Weekend Outlook: April 16-19, 2021

It’s not April 1, and this isn’t a joke – there’s snow in forecast for parts of our area.

Low pressure is moving off the Mid-Atlantic coast this afternoon while an upper-level low pressure area moves in from the west. The upper-level low will draw the surface low northward towards southeastern New England while it intensifies. Rain is spreading across the region this afternoon, and it will become steadier and heavier tonight as the low moves up the coast. With the upper-level low moving in, we’ll have some very cold air aloft. As the rain becomes heavier, it will pull the cold air down from above, a process called “dynamic cooling”. As this occurs Friday morning, we’ll see the rain change over to snow across the hills from northwestern Rhode Island and central Massachusetts into southwestern New Hampshire. Some wet snow may mix in across the lower elevations of southern New Hampshire and northern Massachusetts as well but we’re not expecting much, if any, accumulation, and what does accumulate will be mainly on grassy surfaces because the pavement is too warm, and air temperatures won’t drop below freezing. It’ll be a different story across the hills from Worcester County into the Monadnocks of southwestern New Hampshire, where several inches may accumulate. Even heavier snow is possible for the Berkshires and the Green Mountains of Vermont. We should note that there are some models that are forecasting accumulating snow, and in some cases quite a bit of it, across most of eastern Massachusetts and Rhode Island. While we can’t completely rule out this scenario, we’re not expecting it to occur.

Most of us won’t see much, if any, snow from this system. Image provided by WeatherBell.

The surface low will pass near or over Cape Cod or southeastern Massachusetts Friday afternoon, allowing any mixed precipitation to change back to all rain and milder air moves in. The rain will taper off to showers in the afternoon, but the showers may not completely end until early Saturday as the system slowly starts to move away. Given the recent lack of rainfall, we’re starting to see drought conditions develop. With 1-2 inches of rain expected from this storm, we’ll help put a nice dent in that developing drought.

Much-needed rain is expected over the next 48 hours. Image provided by Weathermodels.com

Saturday won’t be quite as chilly as Friday, but we probably won’t see much sunshine either as the system only slowly moves away. High pressure starts to build in on Sunday with more clearing and milder temperatures. However, an upper-level disturbance will be moving through, so a couple of pop-up showers can’t be ruled out. Patriots Day on Monday is shaping up to be a nice Spring day with partly sunny skies and mild temperatures, but again, a pop-up shower can’t be ruled out as another weak upper-level disturbance crosses the region.

Monday looks to be a mild day. Image provided by WeatherBell.

Thursday night: Periods of rain, possibly heavy at times, changing to snow across the hills from northwestern Rhode Island and central Massachusetts into southwestern New Hampshire, breezy. Low 33-40.

Friday: Windy with rain mixed with snow at times in the morning, tapering off to showers during the afternoon. High 37-44, possibly a little warmer south of Boston.

Friday night: Cloudy and breezy with showers ending. Low 33-40.

Saturday: Plenty of clouds, possibly a few showers near the coast, some sunny breaks may develop in the afternoon. High 44-51.

Saturday night: Partly to mostly cloudy. Low 32-39.

Sunday: Intervals of clouds and sunshine, slight chance for a shower. High 49-56.

Sunday night: Clear to partly cloudy. Low 33-40.

Monday: Partly sunny, slight chance for a shower. High 56-63.

More Snow on the Way

This shouldn’t be a surprise, since it’s February, but there’s snow in the forecast.

Today’s sunshine and cool temperatures are a product of high pressure building in across the eastern Great Lakes. However, as that high slides off to the east, low pressure, currently in the western Gulf of Mexico, will slowly make its way toward the region. However, it’s not as simple as a storm system passing off to the south and bringing in some snow. This will actually be a three-part system that lasts quite a while.

Aside from a few high clouds, most of the Northeast is enjoying sunshine this afternoon. Loop provided by NOAA.

The initial low pressure system will move off the Southeast coast and head northeastward, passing south of the area late Thursday and Thursday night. This will spread some light snow in Thursday afternoon and evening, mainly south of the Mass Pike. As that system pulls away, another weak system will emerge from the Carolina coast, spreading more snow in. This will overspread most of the area. Along the South Coast, we’ll see some milder air move in, especially aloft, which will likely result in some sleet or rain mixing in. That system pulls away early Friday, but yet another weak system follows in its wake, passing south of the area during the day on Friday, with even more snow expected, even down to the South Coast, as some cooler air filters in behind the previous system. That system finally pulls away Friday night, but with an upper-level low pressure system moving across the Northeast, some more snow showers are possible on Saturday.

It’s important to note that this isn’t your classic Nor’easter with a powerful system off the coast, strong winds, and bursts of heavy snow. Instead, we’re just left with a series of weak systems that will produce off-and-on light snow for a period of 24-to-36 hours across the region. Of course, even light snow will add up if it persists for that long, but this isn’t the “blockbuster” 1-to-2 feet that we sometimes receive at this time of year.

So, how much are we expecting?

Central NH (Concord): 2-4″
Southern NH (Manchester/Nashua): 2-5″
NH Seacoast/Merrimack Valley: 3-6″
MetroWest/MetroBoston: 4-7″
Southeastern Massachusetts/RI: 5-9″
South Coast: 4-7″
Cape Cod: 3-6″ (heaviest near the Canal)

The NWS Blend of Models is probably closest to our thinking right now. Image provided by Weathermodels.com

Another system may bring in some light snow or rain on Monday. We’ll have a little more detail on that in our Weekend Outlook tomorrow.

Weekly Outlook: February 15-21, 2021

This week is going to be messy with not one but two different storms that will produce a variety of precipitation across the region.

We start off the week with plenty of clouds and some light snow and/or freezing drizzle this afternoon as a weak system passes well south of the region. However, another storm system will be moving out of the Tennessee Valley and heading our way. This is the same storm that wreaked havoc on Texas and the Southern Plains over the weekend. At one point over the weekend, all 254 counties in Texas were under a Winter Storm Warning. We’re not sure if that has ever happened before, but it’s certainly a rare event. That storm will head northeastward today, moving up the Appalachians. It will then redevelop south of Long Island tonight, and pass near or across southeastern Massachusetts Tuesday morning.

A variety of watches, warnings, and advisories are in effect across the Northeast ahead of the next storm system. Image provided by Pivotal Weather.

With the low passing to our south, cold air will remain in place for much of the region, mainly north and west of Boston. As milder air moves in aloft, we’ll see snow change over to sleet and then freezing rain this evening and tonight. Before it changes over, we’re looking at an inch or less of snow for much of Massachusetts and Rhode Island, with an inch, possibly 2 inches across southern New Hampshire. Once you get north of Concord, NH, several inches are possible before the flip to sleet/freezing rain. An extended period of freezing rain is possible in parts of the area, especially from the Merrimack Valley into Southern New Hampshire. This will obviously result in hazardous driving conditions, but also will increase the threat of power outages due to downed trees and wires from the weight of the ice. From Boston southward, we’re looking at mostly rain, with temperatures above freezing. How far inland that above-freezing air gets is still a question mark, but right now, we’re thinking that areas north and west of Interstate-95 will likely stay below freezing the entire time. Most of the models try to bring the warmer air all the way into the Merrimack Valley or even Southern New Hampshire. However, the models also tend to overestimate how quickly the cold air will erode, especially when there is snow on the ground. Plus, they have significantly underestimated the magnitude of the cold air that moved in across Texas and the Southern Plains over the last few days. For these reasons, we’re going to stay a little colder than the models. Across Cape Cod and parts of southeastern Massachusetts, cold air won’t be an issue, and in fact, temperatures could get to 50 or even warmer for a while Tuesday morning if the storm passes across southeastern Massachusetts instead of just to the south.

Everything winds down by early afternoon, then skies clear out, with colder air returning for Tuesday night and Wednesday as high pressure builds in. From Boston southward, this means that everything will quickly ice back over Tuesday evening as temperatures drop below freezing. Keep this in mind if you’ll be out an about, as many untreated surfaces will become slick. Although Wednesday will feature sunshine, it will be quite chilly, with temperatures likely staying in the 20s to lower 30s, which is as much as 10 degrees below normal.

Temperatures will be 5-10 degrees below normal on Wednesday. Image provided by Weathermodels.com

By Thursday, another system will approach the region, and this one also looks messy, but a little colder. This system will likely stay south of the region, but some milder air will move in aloft. So, once again, we’re looking at snow, changing to sleet and freezing rain, and possibly plain rain in some areas. The airmass ahead of this system will be a little colder than the one we have in place today, so we could be looking at more snow before the changeover, especially from the Merrimack Valley northward. However, this one could also feature a period of freezing rain across the interior. Details like this are nearly impossible to pin down 4-5 days in advance, so we’ll get into more detail towards midweek as things become clearer.

Thursday night and Friday are looking messy once again. Images provided by Pivotal Weather.

High pressure returns next weekend with drier and colder conditions once again. There are some signs that the colder weather we’ve been dealing with for much of the month could start to retreat in Canada next week, but that’s a long ways away, and things can still change.

Above normal temperatures next week? It’s possible, at least according to one model. Image provided by WeatherBell.

Monday: Cloudy with some light snow or snow showers, possibly mixed with a little sleet or drizzle, especially along the coast. High 27-34.

Monday night: Light snow during the evening, mainly from the Merrimack Valley into Southern New Hampshire, eventually changing to sleet and freezing rain, except precipitation falls mainly as rain south and east of Interstate 95. Low 25-32 during the evening, then temperatures may rise a few degrees overnight.

Tuesday: Freezing rain across the interior and rain in the coastal plain ending by early afternoon. High 30-37 north and west of Interstate 95, 38-45 south and east of I-95, potentially as warm as 45-55 across parts of southern Rhode Island, southeastern Massachusetts, and Cape Cod during the morning.

Tuesday night: Clearing, breezy. Low 14-21.

Wednesday: Sunshine and some late-day clouds. High 25-32.

Thursday: Cloudy, light snow is possible late in the day, possibly changing to sleet and freezing rain at night. High 26-33.

Friday: Snow, sleet, freezing rain, and rain ending in the morning, breezy. High 33-40.

Saturday: Intervals of clouds and sun, breezy, a few flurries are possible. High 25-32.

Sunday: Partly to mostly sunny. High 27-34.

Super Snow Sunday?

It seems as though we are getting a snowstorm after all tomorrow. It won’t be a big one, or a long-duration one, but it will impact your Sunday.

At the end of our Weekend Outlook, we mentioned the chance for snow on Sunday, but closed with this:

“Overall, not a big deal for most of us. Parts of the South Coast could see a few inches of snow depending on how far north the ocean storm actually gets, but otherwise, we’re not anticipating much accumulation across the region, unless things change in the next day or two.”

Well, things have changed. Low pressure will move off the Mid-Atlantic coastline tonight, and pass south and east of Nantucket on Sunday, farther north than we were thinking on Thursday. This will result in accumulating snow for most of the region, with this ending up as a moderate snowstorm far parts of southeastern Massachusetts.

Low pressure will pass south and east of the region on Sunday. Loop provided by WeatherBell.

Snow will develop from southwest to northeast during the morning, and from late morning into mid-afternoon, snow may be moderate to heavy at times, with snowfall rates of 1 inch per hour or more. The snow will start to wind down by late afternoon or early evening, just in time for the Super Bowl to begin. For most of us, this will be just a snow storm. However, for parts of Cape Cod and the Islands, there is a chance that some sleet or rain could mix in, which would keep accumulations down slightly.

So, how much are we expecting?

Central NH (Manchester/Concord): 2-4″
Southern NH/North-Central MA: 3-5″
NH Seacoast/Merrimack Valley: 4-7″
The Rest of Eastern MA/RI: 5-9″, except 3-6″ across the Outer Cape and Islands and the immediate east coast of MA

The NWS Blend of models is probably closest to our thinking right now. Image provided by Weathermodels.com

As was pointed out to us by a colleague for parts of Southeastern Massachusetts, this will be one of the biggest storms this area has seen in a few years. Using Middleboro as an example. they have only received 6 or more inches from a single storm twice in the last 3 years – 6.5″ December 2-3, 2019, and 8.5″ on March 4, 2019.

Beyond this, our next chance for some snow will be with another weak system on Tuesday. That storm will produce a little light snow, possibly rain south of Boston. However, given the performance of the models more than a day or two out, would you really be surprised if it becomes something bigger? We’ll have more on that in our Weekly Outlook Monday morning.

Weekly Outlook: February 1-7, 2021

March is supposed to come in like a lion, and it still may, but for now, February is going to as well.

As you may have heard, it’s going to snow today. We’re not going to rehash that too much, since we just wrote a very detailed post about the storm Sunday evening, and our thinking really hasn’t changed much. Suffice to say, snow will become heavy at times this afternoon and tonight, changing to rain for the immediate coast and Cape Cod. It’ll start to wind down early Tuesday, but occasional snow showers and periods of light snow continue on Tuesday with rain eventually going back to snow near the coast. Strong winds this afternoon and tonight slowly diminish on Tuesday as well.

The NWS Blend of Models is still closest to our thinking with snowfall for the current storm. Image provided by Weathermodels.com

So, let’s get to what comes next. On Wednesday, the storm pulls away, heading towards Nova Scotia, but we may still have a few snow showers around, especially during the morning. Skies may start to clear out late in the day. The airmass behind the storm isn’t that cold, so unlike past storms, we don’t have to worry about another arctic blast freezing everything up. High pressure then builds in for Thursday and the sun should return, with temperatures right around where they should be in early February.

Average high temperatures in early February are in the middle to upper 30s across the region. Image provided by Weathermodels.com

Friday and the weekend are when things get interesting again. You may recall a few days ago when some of the tv meteorologists were talking about a big warmup and rainstorm around here for this coming Friday, which would help get rid of a lot of the snow we’re getting today. Well, that’s not quite what’s going to happen now. Yes, low pressure will still travel into the Great Lakes and then Ontario, passing well north and west of us, and temperatures will moderate a bit on Friday. However, temperatures will likely only get into the upper 30s to lower 40s, which is still a little above normal, but not the 50s some of the models were showing a few days ago. We’re also not looking at a lot of rain either. There will likely be some precipitation ahead of a strong cold front, and much of it will be rain, but it might not start as rain across the interior.

The cold front moves through Friday night and high pressure starts to build in with colder air once again. It won’t be as cold as what we had this past weekend, but temperatures will be near to perhaps a little below normal. That’s not the end of the story though. That cold front likely stalls out across the Southeast and then a wave of low pressure will move out of the Gulf of Mexico and start to ride up along the front. Some of the models are showing the potential for that system to bring in some more snow next weekend. It’s still 6-7 days away, and most of the models have not performed that well beyond 2-3 days for quite some time, so we’re not completely convinced of this yet, but it’s something we’ll start to focus on once we get our current storm out of the way. If it starts looking more likely, we’ll have more details in our Weekend Outlook Thursday afternoon.

The models have lots of differences in timing and track of a potential system next weekend. Images provided by Pivotal Weather.

Monday: Becoming windy with snow, heavy at times by late afternoon, changing to rain along the coast. High 28-35.

Monday night: Windy with snow, heavy at times inland, and rain from Cape Cod and parts of southeastern and coastal Massachusetts. Precipitation tapers off toward daybreak. Temperatures hold steady or rise a few degrees overnight.

Tuesday: Cloudy and breezy with periods of light snow and snow showers, except rain showers for southeastern Massachusetts. High 30-37, a little warmer across Cape Cod and possibly southeastern Massachusetts.

Tuesday night: Cloudy and breezy with additional snow showers possible. Low 21-28.

Wednesday: Cloudy with a few more snow showers possible early, some glimpses of sunshine are possible in the afternoon. High 29-36.

Thursday: Partly to mostly sunny. High 32-39.

Friday: Cloudy and breezy with showers developing, possibly starting as snow or a wintry mix north and west of Boston. High 38-45.

Saturday: Some early sun is possible otherwise mostly cloudy with a chance of snow or rain. High 33-40.

Sunday: Mostly cloudy with snow or rain possible. High 32-39.

Here Comes the Snow

We really haven’t had a decent-sized snowstorm around here since mid-December. That will change in a hurry on Monday. As a result, the Extreme Hype Watch we issued on Thursday has been upgraded to an Extreme Hype Warning.

Low pressure moving across the Ohio Valley this afternoon is just one ingredient in the mix for the upcoming storm. Image provided by the Weather Prediction Center.

High pressure remains in place across Quebec, keeping plenty of cold air in place across the Northeast this afternoon. Meanwhile, low pressure is moving across the Ohio Valley, producing a swath of snow from the Great Lakes into the Mid-Atlantic states. As that low moves eastward, it will weaken tonight, but a new area of low pressure will develop off the Mid-Atlantic coastline. At the same time, and upper-level low pressure area will also move toward the East Coast. As the new surface low gets caught underneath the upper-air low pressure area later Monday and Monday night, it will stall out or meander around south of Long Island. Eventually, it will resume an east to northeast motion on Tuesday, passing south and east of Nantucket before moving into the Gulf of Maine.

Snow is falling from Chicago to New York City late this afternoon. Loop provided by Weathertap.

As we mentioned, an Extreme Hype Warning has been issued, which means you’ll see blanket coverage from the network stations around here, hourly updates even when they go to regular programming, and of course, obligatory live shots from (take your pick):

  • The side of an Interstate
  • Logan Airport
  • A local DPW salt pile
  • A beach showing the rough surf and coastal flooding
  • A Dunkin Donuts where they are talking to a plow operator
  • All of the above

You’ll also get network reports about how the snow is creating chaos in New York City, how it put Washington at a standstill, and possibly how it dumped heavy snow on the Midwest. The latter is debatable, because anything west of the Appalachians is considered “flyover country” to the media around here.

OK, we’ve explained what’s going on in the big picture, now let’s focus on some of the details for our area (Southern New Hampshire, Eastern Massachusetts, Rhode Island):

Winter Storm Warnings are in effect from Maine to Virginia.

As you can see on the radar above, snow is already moving into the Tri-State area, and will continue to make slow progress northward tonight. By morning, east to northeast winds will start to increase around here, and we’ll see some ocean-effect snow showers develop in parts of southern New Hampshire and eastern Massachusetts. These aren’t directly related to the storm, but may drop 1/4-1/2″ of snow. This is also a common occurrence before some storms around here. The snowfall from the storm will move in during the late-morning and early afternoon hours and should become moderate to heavy by late afternoon or early evening. Snow may fall at the rate of an inch or two per hour at times. This will continue overnight with precipitation starting to taper off before daybreak. For much of the region, that precipitation will fall as all snow, but a change to rain is likely along the coast and across parts of southeastern Massachusetts and southern Rhode Island. How far inland that rain-snow line penetrates will obviously have a large impact on accumulations. Right now, we don’t expect it to get past Interstate-95, and it might not even get that far.

By Tuesday morning, the steady precipitation will taper off, but the storm will still be south of Long Island. So, what we’re looking at is occasional snow showers and periods of light snow throughout the day, with rain or mixed precipitation in southeastern Massachusetts and southern Rhode Island, This likely won’t add too much accumulation, but in some places, we could see another inch or two. As the low finally gets moving, colder air will work its way back in, changing everywhere back to all snow before it ends late Tuesday night or Wednesday morning.

There are several factors that could cause problems around here. First and foremost is the wind. Northeast winds will increase to 15-25 mph inland, and 20-30 mph along the coast, with gusts of 30-50 mph. This will create near-blizzard conditions at times Monday night, with reduced visibility and blowing and drifting snow. If you don’t have to go out Monday night, stay home. Driving will be extremely hazardous. Across Cape Cod and the Islands, a High Wind Warning is in effect. Sustained winds of 25-35 mph with gusts to 60 mph are possible here. Winds will only slowly diminish across the region on Tuesday.

Peak wind gusts of 40-50 mph are expected across the region. Image provided by WeatherBell.

Along with the wind, we have coastal flooding to worry about. A Coastal Flood Watch is in effect for eastern Massachusetts, mainly for the high tide cycles Monday night and Tuesday morning. Those strong northeast winds, combined with tides that are still astronomically high, will likely produce some coastal flooding, especially in some of the normally prone areas (like Morrissey Boulevard in Boston). By Tuesday afternoon, winds will become more northerly, reducing the coastal flood threat.

Finally, we get to the part you’re all interested in – how much snow? The good news is that they heaviest snow from this storm will likely be south and west of us, from southeastern New York and northern New Jersey into parts of Pennsylvania. Many locations in this area could see 20 or more inches of snow before everything winds down. Even New York City could see a foot to perhaps a foot and a half of snow. Around here, there will likely be many reports in excess of a foot, especially north and west of Boston. As for specifics, here’s what we’re thinking:

Cape Cod: 1-3″, heaviest near the Canal
South Coast/Immediate East Coast: 3-6″
Interior Southeastern Massachusetts/I95 Corridor from RI into Eastern MA: 6-10″
Areas North and West of Interstate-95 (including southern/Central NH): 10-15″ with some heavier amounts possible.

Our thinking is closest to what the NWS Blend of Models is showing. Image provided by Weathermodels.com

Obviously, some of these amounts are dependent on when/if rain starts to mix on or a complete change to rain occurs. Most of the accumulating snow will occur between late Monday afternoon and daybreak Tuesday, but there will still be some snow falling during the day on Tuesday.

Another storm will move in late this week, but this one looks to be milder, with rain for a bigger chunk of the region, though snow is a possibility across the interior. We’ll have more on that in our Weekly Outlook tomorrow morning.

Christmas Weekend Outlook: December 24-28, 2020

We’ve got a couple of busy days coming up, and not just because it’s Christmas.

Low pressure is moving across Iowa this afternoon, producing blizzard conditions across parts of the Upper Midwest and Northern Plains. That system will impact us over the next few days, but in a different way. As it moves toward the Great Lakes, it will start to send milder air into the region tonight, but more noticeably tomorrow. Southerly winds will gradually increase tomorrow, becoming quite strong tomorrow night and into Christmas morning. Sustained winds of 15-30 mph are likely, with wind gusts to 50-60 mph or more possible. This could result in power outages, so don’t be surprised if you wake up Christmas morning and can’t charge up those new electronics you found under the tree.

Damaging wind gusts are possible across much of the region Thursday night and Christmas morning. Image provided by WeatherBell.

Wind isn’t the only issue we’ll have. Rain will move in Thursday night, and continue into Christmas Day. While it may not be raining the entire time, there will be some bands of heavy rain, with rainfall totals in excess of an inch possible in many areas. The rain, combined with temperatures climbing above 50, will help to melt a lot of the snow that is on the ground. This could result in some flooding issues in some spots, but widespread flooding doesn’t look likely.

The ECMWF shows how our snow cover could quickly disappear over the next few days. Loop provided by Weathermodels.com

As this storm system moves into southeastern Canada, it will drag a strong cold front across the region on Christmas Day. Although the day will start mild, likely in the 50s for most of us, temperatures will drop during the afternoon. If the cold air moves in fast enough and the precipitation is slower to move out, we could even see some wet snowflakes before everything winds down late in the day. At night, temperatures will continue to drop, meaning that the wet roads will likely start to ice over if they are not treated, as they won’t have had much time to dry before the cold air moves in.

The GFS model shows the warmer air move in on Christmas Eve, then quickly get replaced on Christmas Day. Loop provided by WeatherBell.

High pressure builds in for the weekend with dry and seasonably cold conditions. It may still be a bit breezy on Saturday, adding to the chill, but Sunday may also be a few degrees milder. By Monday, we’ll be watching another storm system passing to our west, with some showers possible.

Wednesday night: Becoming partly to mostly cloudy. Low 23-30 this evening, but temperatures may start to rise a bit after midnight.

Christmas Eve: Mostly cloudy, becoming breezy in the afternoon. High 48-55.

Thursday night: Cloudy and windy with showers developing, becoming steady rain late at night. Temperatures gradually rise overnight.

Christmas Day: Cloudy with rain likely, possibly heavy at times, windy in the morning. High 53-60 in the morning, temperatures drop during the afternoon.

Friday night: Mostly cloudy and breezy with any lingering showers ending in the evening, possibly mixed with a few wet snowflakes, some clearing is possible late at night. Low 22-29.

Saturday: Becoming partly to mostly sunny. High 28-35 (welcome back to December).

Saturday night: Clear skies. Low 19-26.

Sunday: Partly to mostly sunny. High 32-39.

Sunday night: Increasing clouds. Low 22-29.

Monday: Mostly cloudy and breezy with a few showers possible. High 42-49.

Snow is On the Way

After several days of media hype, and people posting model forecasts for extreme amounts of snow on social media, it looks like we do actually have a snowstorm on the way, and it could be a decent-sized one for parts of the region.

High pressure over Ontario and low pressure over Texas are two things we need to pay attention to for the next day or two. Image provided by NOAA.

Low pressure over Texas this afternoon will combine with a second area near the Texas coast to become a single storm system later today, which will then head northeastward into the Tennessee Valley tonight, bringing plenty of moisture with it from the Gulf of Mexico. Meanwhile, a strong high pressure system is moving across southeastern Canada, bringing plenty of cold air into the Northeast. When you get copious amounts of moisture running into cold air, you end up with snow, potentially a lot of it,. That’s what’s going to happen here late Wednesday into Thursday.

Winter Storm Watches are in effect for all of Southern New England. Image provided by Pivotal Weather.

That low pressure area will move from the Tennessee Valley to the Mid-Atlantic coastline on Wednesday before moving offshore and passing south of New England. While there are still some questions as to the exact track it will take, which has implications for the forecast itself, the models have come into better agreement today on a more northerly track than they were showing last night. This has several implications for the forecast around here:

1. Snow will likely penetrate even farther inland, with heavier snow farther inland as well.
2. Rain/snow ratios will be lower across southeastern New England, resulting in a wetter snow.
3. A change to sleet or rain is now possible across Cape Cod, and possibly parts of southeastern Massachusetts and southern Rhode Island.

We mentioned in our Weekly Outlook that there would likely be a sharp cutoff in the northern extent of the snow, going from heavy snow to little snow in a short span, but we weren’t sure where that cutoff would set up. At this point, it’s looking more and more likely that it will set up somewhere in central or southern New Hampshire, meaning that most of us will be shoveling by Thursday morning. This detail is still not definite, so obviously things can change in the next 24 hours or so.

Plenty of cold air will be in place before the storm moves in. Image provided by Weathermodels.com

That high pressure area in southeastern Canada will provide us with plenty of cold air, which will be evident tonight when temperatures drop into the teens or even single numbers. As the snow moves in Wednesday night, we’ll see a coastal front setup across eastern Massachusetts and Rhode Island. This is a common occurrence in winter storms. Basically, the northeast to east winds off the water send temperatures up to the lower to middle 30s along the coast and a short distance inland (anywhere from 20-40 miles). On the other side of that front, northeast to north winds keep the colder air locked in, with temperatures in the teens and lower 20s. Obviously, in the “milder” air on one side, you’ll get a wetter snow, with the possibility of some mixed precipitation, while the colder area gets mostly snow that is more powdery. We said “mostly snow”, as you can get some milder air aloft which could allow for some sleet to mix in, which obviously would have a significant impact on snow accumulations. That coastal front will eventually collapse southeastward toward the coast as the low pressure area moves by, allowing the colder air to eventually move back in everywhere, and any mixing that does take place eventually goes back over to all snow.

The snow to rain ratio varies by temperature, as this chart shows. Image provided by Weathertrends360.com

As for the timing, most of Wednesday should be fine, so you can do any errands that need to be completed before the storm moves in. Snow should move into the South Coast towards the evening rush, quickly spreading northward, reaching the MA/NH border by midnight. Snow may fall moderate to heavy at times overnight, with some mixing possible across Cape Cod and the Islands (and possibly southeastern Massachusetts) late at night and early Thursday morning. Most of the steady precipitation should wind down by midday, but some lingering snow showers are possible, especially along the coast, through the afternoon.

Snow isn’t the only threat with this system, as gusty winds are also expected, especially along the coastline. While this storm won’t be that strong, at least compared to many winter storms in the past, the gradient between it and the large high pressure area to the north will create some gusty winds. Sustained winds of 15-25 mph, with gusts to 40 mph or more, are likely. These gusty winds may enhance the snow across parts of eastern Massachusetts. However, with high astronomical tides, the winds may also result in some coastal flooding around high tide, especially at northeast and east facing coastal areas.

Wind gusts to 40 mph or more are possible, especially along the coast. Image provided by WeatherBell.

So, how much snow are we looking at? Obviously, there’s still some things that complicate this part of the forecast (snow ratios/mixing/northern extent of the snow), so this is preliminary for now, and we may adjust it tomorrow if needed, but here’s our thinking:

Central New Hampshire: 2-4″
Southern New Hampshire/Seacoast: 4-8″
Merrimack Valley/Central Massachusetts: 5-10″
North Shore/MetroWest/Metro Boston: 6-12″
Interior Southeastern Massachusetts/Rhode Island: 8-14″
Cape Cod and the Islands: 4-8″

This model is probably closest to our thinking on snow accumulations at the moment. Image provided by Pivotal Weather.

Colder air will settle back into the region behind the storm for Thursday night and Friday, so you’ll want to clear out the driveways and walkways before everything freezes solid.

Weekly Outlook: December 14-20, 2020

Hope you enjoyed the 60-degree temperatures on Sunday, because changes are coming. It’s going to snow this week, likely more than once for many of us.

Sunday was a mild day across most of the region. Image provided by NOAA.

A cold front moved across the region overnight and is now south of us. Low pressure will move off the Mid-Atlantic coastline and ride along that frontal system today. Precipitation will move in towards midday and continue through the afternoon, ending in the evening. Temperatures will be near or above freezing, so we’ll see a mix of rain and snow, likely changing over to snow before ending in many areas as colder air filters in behind the system. We’re not expecting much accumulation, mainly an inch or so, and mainly south of the Mass Pike. A few places could see up to 2 inches in heavier bursts, but overall this isn’t a big deal. However, since it will fall during the afternoon, it could make a mess of the afternoon commute, so keep that in mind if you are not working from home. North of the Mass Pike, we’re only looking at some flurries, if that, with the ground getting coated in some locations.

Not much snow is expected today, but the timing will make it a bit more impactful. Image provided by WeatherBell.

That storm will move into Atlantic Canada on Tuesday, and strengthen into a powerful storm system. Gusty northwest winds behind the storm will usher much cooler air in for Tuesday and Wednesday as high pressure moves into southeastern Canada. This will become important as we head into later Wednesday and Thursday as the next storm system moves towards the area.

Wednesday morning could be rather chilly across the region. Image provided by Weathermodels.com

As you’ve no doubt heard by now, a rather strong storm system will impact the East Coast later Wednesday into Thursday. With high pressure to the north, we’ll have plenty of cold air in place, so anything that does fall will almost certainly fall in the form of snow. As the storm strengthens, it will produce gusty winds in some areas, which combined with the high astronomical tides, could result in some coastal flooding, especially east and northeast-facing locations. Beyond that, there’s a lot of uncertainty. That storm that moved into Atlantic Canada will not move too much, and it will have an impact on the track our mid-week storm takes. Another factor will be the high pressure area to our north. It will try to send cool and dry air southward into the region. This will likely result in a sharp cutoff of the precipitation, going from heavy snow to virtually no snow over a relatively small area. Where that cutoff sets up is also still in question. The models, while in general agreement that a powerful storm will move off the Atlantic Coast and south of New England, differ on some of the finer details, which have an enormous impact on the forecast. It’s still WAY too early to pin down any specifics, so we won’t bother to attempt it. We’ll just say that the potential exists for a significant snowstorm across the region from late Wednesday into Thursday. Beyond that, we’ll offer more details in a special blog post on Tuesday.

Differences among the models can have a big impact on the forecast for the storm around here. Images provided by Pivotal Weather.

Behind the storm, high pressure builds back in for Friday and Saturday with dry and chilly conditions. If there’s fresh snow on the ground, some places could get quite chilly at night, especially Thursday night and Friday night. By Sunday, the high moves offshore and temperatures will start to moderate. However, another system may bring in some rain or snow. We’ll worry about that one after we get through the first two.

Monday: Cloudy with rain or mixed precipitation developing around midday, eventually changing to light snow by late afternoon. High 32-39.

Monday night: Light snow ends in the evening, then skies clear out overnight. Low 23-30.

Tuesday: Sunshine and some afternoon clouds, breezy. High 28-35.

Tuesday night: Clear during the evening, clouds move in late at night. Low 12-19.

Wednesday: Cloudy and becoming breezy with snow possible late in the day and at night. High 24-31.

Thursday: Cloudy and windy with snow likely, ending during the afternoon. High 24-31.

Friday: Partly to mostly sunny. High 27-34.

Saturday: Sunny in the morning, clouds return in the afternoon. High 30-37.

Sunday: Cloudy with a chance of rain or snow. High 37-44.

Stormy Saturday on Tap

The first snowstorm of meteorological winter is expected across at least part of the region on Saturday.

Low pressure is moving into Tennessee this afternoon, on its way toward the Northeast. Image provided by the Weather Prediction Center.

Low pressure moving into the Tennessee Valley this afternoon will cross the Appalachians tonight and move off the Mid-Atlantic coastline on Saturday. Ahead of it, rain will move into our area tonight, and it could be heavy Saturday morning. Given our long-term rainfall deficit, this is a good thing. However, some localized flooding is possible, especially in areas where the storm drains are covered or clogged by fallen leaves. This is the easy part of the forecast.

Rainfall totals of 1-2 inches are possible across much of the area from this storm. Image provided by Weathermodels.com

As the system moves northeastward, an upper-level disturbance will drop southeastward from Canada. This disturbance and the system to the south will eventually phase, resulting in a fairly strong storm system off the East Coast. There is still some question to the exact track the system takes, but it will likely pass close to or just south of Cape Cod and the Islands. As the system intensifies, it will generate some strong winds, especially along the coast south of Boston. High Wind Watches have been posted along the coast in this area, where sustained winds of 25-35 mph are expected, with some gusts to 50 mph or more possible.

Wind gusts of 50 mph or higher are possible along the coast late Saturday and Saturday night. Image provided by WeatherBell.

As the storm passes by our longitude, it will turn winds from the northeast to the north and eventually northwest. This will help bring colder air down from the north. The airmass to the north isn’t that cold by December standards, but temperatures will drop below freezing, which will allow for the rain to change over to snow from northwest to southeast as the low passes by. The exact track of the storm will determine exactly where the rain/snow line ends up. A track farther to the north and west results in less snow to the south and east.

The models still have a wide variety of ideas for how much snow is expected and where it will fall. Images provided by Pivotal Weather.

When that changeover occurs also will have a big impact on the snowfall amounts. Right now, here’s our thoughts on the changeover timing:

Late morning: The higher terrain from central Massachusetts into southwestern New Hampshire
Midday/Early Afternoon: Southern New Hampshire
Early/Mid Afternoon: Merrimack Valley and New Hampshire Seacoast
Late Afternoon: MetroWest and the North Shore as well as Northern Rhode Island
Early Evening: I-95 corridor from Boston to Providence and parts of Southeastern Massachusetts.

Everything should wind down and end by midnight as the storm moves into the Gulf of Maine and pulls away from the area.

Beyond the timing and track issues, we have one more thing that complicates the snowfall forecast. As the system gets cranked up, bands of very heavy snow will develop. Some of these bands may produce 1-2 inches of snow in an hour. Exactly where those bands set up is nearly impossible to determine in advance, and even trying to figure out a general area for them is tough, because part of it will depend on the track of the system.

Having said all of that, here’s our best estimate right now for snowfall:

Dusting (if that): Cape Cod and the Islands
1-2″: Southeastern Massachusetts and Southern Rhode Island
2-4″: I-95 corridor from Boston to Providence
3-5″: Northern Rhode Island/MetroWest/North Shore/New Hampshire Seacoast
4-7″: Merrimack Valley/Southern New Hampshire
5-9″: Worcester County/Southwestern New Hampshire

Obviously this is a low-confidence forecast, based on all of the factors above, but it’s our best guess at the moment. If there’s any significant changes, we may do another quick update Saturday morning/early afternoon.

The next few days after the storm look calmer, but another system will develop off the East Coast on Tuesday. Right now, it looks like it will stay too far south and east to have any impacts here, but we’ll keep an eye on it.