Author: wxmanscottk

Weekly Outlook: December 21-27, 2020

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We’ve reached the last full week of the year, and also the winter solstice. Winter officially begins at 5:02am, so by the time most of you read this, astronomical winter will have begun. That doesn’t mean it will feel like winter every day this week.

If you’re heading out early this morning, use a little extra caution, as there may be some black ice, especially away from the coastline. If you’re down the Cape, there’s some rain around this morning, but it should be gone by midday as a low pressure area pulls away from the region. For the rest of us, today will just be a cloudy day, with temperatures fairly typical of late December. We may get a few breaks in the clouds this evening, which would allow you to view the conjunction between Saturn and Jupiter. Otherwise, it’ll remain mostly cloudy overnight and into Tuesday as another weak system moves through with a few rain or snow showers. Once that system moves through, we clear out for Wednesday as high pressure builds in, but it will be chilly.

Some breaks in the clouds this evening may allow you to view the Conjunction of Saturn and Jupiter. Image provided by WeatherBell.

This brings us to Christmas Eve. Low pressure will be heading into the Great Lakes, with milder air moving in ahead of it. Many of the forecast models are showing the potential for strong winds, heavy rainfall, and unseasonably warm temperatures for Christmas Eve into early on Christmas Day before a strong cold front moves across the region. Given the recent performance of the models this far in advance, plus some of the model trends we’ve already seen, we’re a bit skeptical. Yes, we expect it to be mild with some rain. However, we’re not yet convinced that temperatures will be in the upper 50s to lower 60s with 1-2 inches of rain (or more), like many of the models are showing. The system will drag a strong cold front through on Christmas morning, with temperatures dropping quickly on Christmas Day. Now, it won’t be anything like Christmas Day in 1980, but it will be enough for any untreated surfaces to ice up, and possibly for some snow showers. We’ll obviously have a better idea about this system in our Weekend Outlook, which will likely be published on Wednesday this week.

Most of the models are showing the potential for 1-2 inches of rain (or more) Christmas Eve into Christmas Day. Images provided by Pivotal Weather.

(For those wondering, the temperature in Boston on Christmas Day, 1980 was 35 degrees at midnight. A strong cold front moved through just after midnight, and the temperature dropped to -7 by 10am, and only got back up to -2 in the afternoon. Add in the northwest winds of 10-20 mph all day long and it was a brutally cold day.)

Behind that system, high pressure will build in next weekend with drier and colder weather, which is pretty much what you’d expect in late December. There are some indications that our active pattern may continue into next week with more storminess possible.

Monday: Showers end across Cape Cod in the morning, otherwise, plenty of clouds with a few sunny breaks High 35-42.

Monday night: Partly to mostly cloudy. Low 23-30.

Tuesday: Intervals of clouds and sunshine with a rain or snow shower possible. High 35-42.

Tuesday night: Clear to partly cloudy. Low 21-28.

Wednesday: Sunshine fades behind increasing late-day clouds. High 33-40.

Christmas Eve: Cloudy and breezy with showers possible late in the day, and a period of steady rain likely at night. High 43-50.

Christmas Day: Rain may change to snow before ending around midday. High 45-52 early, then temperatures quickly drop in the afternoon.

Saturday: Partly sunny. High 26-33.

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

Snow is On the Way

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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

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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.

Weekend Outlook: December 11-14, 2020

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Another stormy weekend is on tap, but it shouldn’t be anywhere near as bad as last weekend was.

High pressure will remain in control of the region into Friday, with generally dry weather and moderating temperatures. However, low pressure will be heading towards the Great Lakes, sending cloudcover our way, though Friday will still be a decent day around here, by mid-December standards at least.

We still need more rain to alleviate drought conditions, and this weekend will help. Image provided by the National Drought Mitigation Center.

By Saturday, that low will be moving across the Midwest, resulting in a few things happening around here. Some rain will move in late in the day and at night, likely ending Sunday morning. While it’s not expected to be heavy, it will make for a wet Saturday night and Sunday morning. The storm will also send a warm front toward the region, but this is where things get tricky, because we’ll also have a strong high pressure area in southeastern Canada. That high will send cooler air down into the region – meteorologists refer to this as “cold air damming”, as both the mountains to the west and the warm front to the south act as a dam to prevent the cold air from advancing. That warm front likely doesn’t get much past the Mass Pike Saturday night, which keeps areas north of the Pike on the cool side. Meanwhile, a wave of low pressure will ride along that front, keeping the cold air locked in from southern New Hampshire into the Merrimack Valley. Temperatures will likely be in the middle to upper 30s in these areas, but if they are just a few degrees cooler, then we may have to worry about the rain becoming freezing rain. If you’ve got plans in these areas Saturday night, keep an eye on the conditions before you head out.

Most of the models show the warm air staying south of the Mass Pike Saturday evening. Images provided by Pivotal Weather.

By Sunday, the main low pressure area moves into southeastern Canada, dragging a frontal system across the region. As winds shift into the west, it will scour the cold air out, bringing milder air in. For areas south of the Mass Pike, where the warm air will already be in place, temperatures will actually cool off a bit behind the front on Sunday. High pressure returns on Monday with cooler air drier conditions.

Finally, we’ll just address this now, before the hype gets out of control. Yes, there are some models that show the potential for a snowstorm towards the middle to latter half of next week. However, not all of the models show that. Plus, most of the models have done a relatively poor job forecast beyond about 3-4 days out for quite a while now. So yes, there is the “potential” for something next week. There’s also the “potential” that the Patriots will win the Super Bowl again this season. That’s all it is for now – potential. We’ll address it in a bit more detail in out Weekly Outlook Monday morning, if the potential is still there.

Thursday night: Clear to partly cloudy. Low 21-28.

Friday: Sunshine dimmed by afternoon high clouds. High 45-52.

Friday night: Thickening clouds. Low 27-34 north of the Mass Pike, 35-42 south of the Pike.

Saturday: Cloudy with showers developing by late afternoon. High 41-48 north of the Mass Pike, 49-56 south of the Pike.

Saturday night: Scattered showers, possibly some freezing rain across parts of southern New Hampshire. Low 32-39 north of the Mass Pike, 40-47 south of the Pike.

Sunday: Any lingering showers end in the morning, some afternoon sunny breaks are possible. High 47-54.

Sunday night: Partly cloudy. Low 30-37.

Monday: Partly sunny. High 37-44.

Weekly Outlook: December 7-13, 2020

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We’ve got a fairly quiet week coming up across the region with a moderating trend as well.

We start the week off with high pressure in control, providing us with dry and cool conditions. We’ll start off sunny, but high clouds will start to stream in during the afternoon ahead of low pressure moving off the Carolina coast. That system will pass well to our south and east on Tuesday, but the flow around it, moving over the still relatively mild ocean, could help generate a few ocean-effect rain or snow showers, mainly across Cape Cod and east-coastal Massachusetts, especially coastal Plymouth County and Cape Ann. That system pulls away Tuesday night, but another weak upper-level disturbance swings through on Wednesday. Moisture will be limited with this system, but again, a few rain or snow showers can’t be ruled out, mainly well north and west of Boston. High pressure builds in again for Thursday and Friday with generally dry weather and moderating temperatures.

Temperatures should start to moderate by Thursday. Image provided by Weathermodels.com

Things start to get active again next weekend. Most of the models show a low pressure area heading into the Great Lakes and then southeastern Canada. This would result in a warmup around here with some rain likely as the storm drags a frontal system toward the region. However, most of these same models showed a similar scenario for the storm we just had on Saturday. Also, some of the members of the various ensembles show the potential for a secondary area of low pressure to develop south of New England, a common occurrence with low pressure areas that pass well to our west. If this were to happen, it would result in the warm air never making it in here. Now, this doesn’t mean we’ll be in for another snowstorm. It also doesn’t mean that we won’t get well into the 50s with more rain. Obviously, things can and will change as we head through the week. Consider our forecast for next weekend to be “low confidence” right now.

Several members of the GFS Ensemble show a secondary area of low pressure near or south of Southern New England next Sunday. Image provided by WeatherBell.

Monday: Sunshine fades behind thickening afternoon clouds. High 32-39.

Monday night: Partly to mostly cloudy, a few flurries may develop late at night near the east coast. Low 19-26.

Tuesday: More clouds than sun, a few rain or snow showers possible near the coast. High 29-36.

Tuesday night: Partly to mostly cloudy. Low 17-24.

Wednesday: Mostly cloudy, slight chance for a rain or snow shower, favoring areas north and west of Boston. High 34-41.

Thursday: Plenty of sunshine. High 40-47.

Friday: Sunshine dimmed by some afternoon high clouds. High 40-40.

Saturday: Plenty of clouds with showers possible, mainly late in the day and at night. High 47-54.

Sunday: Cloudy with a chance for more showers, mainly early. High 49-56.

Saturday Storm Update

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Our storm is well underway, and we’ve got some changes to the forecast.

Low pressure is taking shape off the Mid-Atlantic coast this morning. Image provided by the Weather Prediction Center.

In the big picture, not a lot has changed this morning. Low pressure is just east of the Delmarva Peninsula this morning, and it will head northeastward today, intensifying rapidly as it passes close to or over Nantucket this afternoon, before heading into the Gulf of Maine tonight. Rain has overspread the region this morning, and has been heavy at times, while temperatures have dropped into the middle 30s to lower 40s. Across the higher elevations of Worcester County, the Monadnocks of southwestern New Hampshire, and the Berkshires, the rain has changed over to snow already.

Heavy rain is falling in many areas with a change to snow across the higher elevations of the interior. Loop provided by Weathertap.

Most of this is in line with the forecast we posted yesterday, the timing is just a little quicker. There still isn’t a lot of cold air to work with at the surface, but the storm is quite intense, and the heavier precipitation is dragging the cold air down from aloft. This will allow the rain to change to snow as the day goes on across much of the remainder of the region from west to east. Temperatures likely will stay in the lower 30s, so it will be a heavy, wet snow, and if the intensity lightens up, it could flip back to rain in spots. This could mean the difference between several inches of snow in one spot, and much less in a nearby location. Along the coast, where water temperatures are still in the 40s, it will take a little longer to flip to snow, thanks to the moderating influence of the marine air.

We’ll also have some strong winds to deal with later today, especially along the coastline. High Wind Warnings and Wind Advisories have been posted for parts of the region. Sustained winds of 20-30 mph and gusts to 50 mph or more are expected, mainly this afternoon and evening as the storm center passes near and just east of the region. Some gusts to 60 mph or more can’t be ruled out, especially across coastal Plymouth County along with Cape Cod and the Islands.

Strong winds are likely this afternoon and evening, especially near the coast. Image provided by WeatherBell.

Here’s where there is still some unknowns. There are likely to be bands of very heavy snow that develop as the system really gets cranked up. These could produce snowfall totals of 1-3 inches per hour. Where they set up is extremely difficult to predict in advance, and these bands could be as little as 5-10 miles wide. We’ve already had one band of very heavy rain setup from Worcester northeastward to the Merrimack Valley this morning. The western edge of this band changed to snow in the higher elevations in Worcester County. Similar bands are likely to form later today. Places just outside these bands could see significantly less snow these spots just a few miles down the road that get stuck under the bands. This obviously complicates the snowfall forecast.

Here’s our updated thoughts on the changeover timing:

Mid/Late morning: The higher terrain from central Massachusetts into southwestern New Hampshire
Late Morning/Midday: Southern New Hampshire
Midday/Early Afternoon: Merrimack Valley and New Hampshire Seacoast
Early/Mid Afternoon: MetroWest and the North Shore as well as Northern Rhode Island
Late Afternoon/Early Evening: I-95 corridor from Boston to Providence and 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. As for snowfall, there is still a wide range among many of the models, so forecast confidence is still below average.

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

Dusting (if that): Cape Cod and the Islands
1-3″: Southeastern Massachusetts and Southern Rhode Island
3-5″: I-95 corridor from Boston to Providence
4-7″: North Shore/New Hampshire Seacoast (heaviest inland)
5-9″: Merrimack Valley/Southern New Hampshire/MetroWest/Northern Rhode Island
6-12″: Worcester County/Southwestern New Hampshire

Some of the hills in Central Massachusetts and Southwestern New Hampshire, especially above 1000 feet, will likely see more than a foot.

The storm is already underway, but there is still a wide range in snowfall forecasts among the model. Images provided by Pivotal Weather.

Once the system passes by, we’ll have drier and cooler weather for the next several days. The only possible fly in the ointment is another system that is expected to pass well south and east of the region on Tuesday. Right now, it should be too far offshore to have much, if any, impact on our area, but we’ll keep an eye on it.

Stormy Saturday on Tap

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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.

Weekend Outlook: December 4-7, 2020

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It looks like we’ve got some snow coming in this weekend for at least part of the region, but that’s only part of a complex forecast for the next few days.

High pressure will slide offshore later today and tonight while clouds start to stream in ahead of a cold front. That front may produce a few showers on Friday, but most of us will just see some clouds as the front moves through. However, this will set the stage for the next storm.

Enjoy the mild weather on Friday, because changes are coming. Image provided by Weathermodels.com

Low pressure currently near the Louisiana coastline will head northeastward tonight, moving up the Appalachians on Friday, then off the Mid-Atlantic coastline on Saturday. At the same time, an upper-level disturbance in Canada will dive southeastward. As these two systems meet up or “phase”, they will create a strengthening low pressure system. The track of that low will determine several things, but the two main ones are how much precipitation will fall, and whether it will be rain or snow. Most of the models bring the storm near Cape Cod or just south of it, but there are others that bring it across southeastern Massachusetts. The farther north and west the low travels, the farther north and west the rain/snow line ends up.

There are still some significant differences among the models for the weekend storm. Images provided by Pivotal Weather

Before we get too far ahead of ourselves, let’s get to what we are fairly sure about. Rain will develop across the region early Saturday morning, and may fall heavy at times during the day on Saturday. This will help put another dent in our long-term rainfall deficit. As the low passes by, northerly winds will bring cooler air into the region. There’s not a lot of “cold” air to begin with, but temperatures will likely drop to near or below freezing, which will allow for a changeover to snow, at least north and west of Boston. That changeover is likely to occur Saturday night, but at least one model has it change over much earlier – during the afternoon. Others only have the changeover occur as the precipitation winds down and ends Sunday morning, and at least one other doesn’t have it changeover at all. Obviously when that changeover occurs will have an impact on how much snow (if any) accumulates.

Whether it’s all rain or rain to snow, this will be another heavy precipitation producer. Image provided by WeatherBell.

Right now, we’re expecting a change to snow from northwest to southeast Saturday evening and night, with everything winding down around daybreak Sunday. The snow could be heavy at times during Saturday evening, but should taper off at night as the system starts to pull away. Several inches could accumulate well north and west of Boston, but this is still a bit uncertain. We’re not going to forecast any amounts yet, as there’s not enough confidence yet to come up with specific amounts. We’ll do another blog post just on the storm tomorrow, and at that point we’ll have a specific snowfall forecast.

Skies should start to clear out Sunday afternoon as gusty west to northwest winds will bring drier air in behind the storm. High pressure will start to build in on Monday, but with an upper-level low pressure system moving through, we’ll still have some clouds, and a few rain or snow showers are possible.

Thursday night: Becoming mostly cloudy. Low 32-39.

Friday: Mostly cloudy, becoming breezy, chance for a few showers, mainly south of the Mass Pike during the afternoon. High 49-56.

Friday night: Cloudy with some showers developing. Low 35-42.

Saturday: Cloudy and windy with rain, heavy at times, changing to snow from central Massachusetts into southern New Hampshire late in the day. High 39-46 early (47-54 across Cape Cod and the Islands), then temperatures drop during the afternoon.

Saturday night: Cloudy and windy with rain changing to snow from northwest to southeast before tapering off and ending toward daybreak. Low 25-32, a little milder across Cape Cod and the Islands.

Sunday: A few lingering rain or snow showers early, then clearing in the afternoon, breezy. High 33-40.

Sunday night: Clear to partly cloudy. Low 19-26.

Monday: A mix of sun and clouds, slight chance for a rain or snow shower. High 32-39.

Weekly Outlook: November 30 – December 6, 2020

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It won’t feel like the last day of November as we start the week on a windy, warm, and wet note.

A strong storm system will move up the Appalachians today, passing west of the region. This will allow unseasonably mild air into the area on gusty south to southeast winds. Sustained winds of 25-35 mph are expected, with some gusts of 50-60 mph (or higher) possible, especially near the coast. Temperatures will get well into the 50s across the region today, with many areas, especially in eastern Massachusetts possibly topping 60 by late in the day. The warm weather will be accompanied by rain, some of which may be heavy at times this afternoon and evening. A few thunderstorms are possible as well. By the time everything winds down at night, much of the region will have received 1-2 inches of rain, with some heavier amounts possible.

Heavy rain is expected across much of the region today. Image provided by Weathermodels.com

As the system moves into southeastern Canada on Tuesday, it will drag a cold front across the region. The day will start off mild, with temperatures in the upper 50s and 60s during the morning, but they’ll drop during the afternoon behind the front. A few more showers are also possible, but nothing as heavy as what we’re expecting today.

The NAM model shows the warm air move in today, remain in place into Tuesday morning, then colder air moves in Tuesday afternoon and night. Loop provided by WeatherBell.

By Wednesday, an upper-level low pressure system will move into the Northeast and southeastern Canada, bringing much cooler air in, though it will still be close to normal for early December. We’ll still have plenty of clouds around, and a pop-up shower or two can’t be ruled out, maybe even a snow flurry. High pressure then builds in for Thursday with sunshine. Clouds return Thursday night and Friday along with milder weather ahead of the next storm system.

Next weekend looks unsettled, but pinning down specifics at this point is an effort in futility. The models have performed relatively poorly beyond a few days lately, and there are significant differences in their solutions for next weekend as well. For now, we’ll just go with unsettled conditions, and the chance for some rain both Saturday and Sunday, but there is a possibility that the entire weekend won’t be unsettled. There’s also the possibility that all of the precipitation that falls wouldn’t be just rain. It will be early December, so this shouldn’t be a big surprise. We hope to have much more clarity on this when we write our Weekend Outlook on Thursday.

The models have no idea what to do with a potential storm next weekend. Image provided by Pivotal Weather.

Monday: Cloudy and becoming windy with rain, possibly heavy at times, maybe a thunderstorm as well. High 55-62.

Monday night: Mostly cloudy with diminishing winds, showers taper off toward midnight. Temperatures hold steady overnight.

Tuesday: More clouds than sun, breezy, chance for a few more showers. High 56-63 early, then temperatures drop in the afternoon.

Tuesday night: Becoming clear to partly cloudy. Low 31-38.

Wednesday: Intervals of clouds and sunshine, breezy, slight chance for a sprinkle or flurry. High 39-46.

Thursday: Mostly sunny, some high clouds may start to stream in late in the day. High 41-48.

Friday: Mostly cloudy, showers possible late in the day. High 47-54.

Saturday: Mostly cloudy and breezy with a chance of rain. High 43-50.

Sunday: Mostly cloudy and breezy with a chance of rain. High 42-49.

Stormy Weather Ahead for the East

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A rather potent storm system will bring a variety of weather to the eastern third of the United States over the next few days.

Low pressure is developing along a frontal system in southern Texas this evening. Image provided by the Weather Prediction Center.

Low pressure developed along a frontal system in southern Texas on Saturday, and it will slowly strengthen as it moves northeastward tonight and Sunday. As it strengthens, it will draw moisture northward from the Gulf of Mexico, while colder air continues to move southward behind the storm system. This will set the stage for a couple of rather active days across the Eastern third of the nation, with several different types of weather likely.

The GFS model shows the progression of the storm over the next few days. Loop provided by Tropical Tidbits.

The biggest threat initially will be severe weather. As the warm, moist air flows northward from the Gulf of Mexico and clashes with the colder air moving in behind the storm, strong to severe thunderstorms are possible. A few storms are possible overnight in parts of Texas and Louisiana, but the threat will shift into the Gulf Coast on Sunday, parts of the Southeast and the Carolinas Sunday night, and parts of the East Coast from Florida to the Mid-Atlantic states on Monday. Some of the stronger storms may produce heavy downpours, damaging winds, and possibly some tornadoes.

Strong to severe storms are possible from the Gulf Coast into the Carolinas on Sunday. Image provided by Pivotal Weather.

While severe weather is not common at this time of year, it is certainly not unheard of. In fact, Saturday marked the 32nd anniversary of one of the strongest tornadoes on record to hit North Carolina. On November 28, 1988, an F4 tornado tore an 84-mile path of damage across parts of North Carolina, including the city of Raleigh.

As the storm moves up the Appalachians it will bring unseasonably mild air to the East Coast, but also some heavy rainfall. Temperatures will be in the 60s and 70s across the Gulf Coast and Southeast on Sunday. By Monday, 60-degree readings will be possible as far north as southern New England, with some 70s into the Carolinas and parts of southern Virginia. The mild air may linger into Tuesday across parts of New England as well. While these temperatures are 10-20 degrees above normal, they will likely fall short of the record highs in most locations.

Monday will be a warm day by November standards up and down the East Coast. Image provided by WeatherBell.

The warm weather will be transported in by strong southerly winds ahead of the system. Sustained winds of 25-35 mph will be common up and down the East Coast. Many places could see wind gusts of 50-60 mph or stronger, which could lead to power outages as trees and wires come down.

Wind gusts in excess of 50 mph are possible across the East Coast ahead of the storm. Image provided by WeatherBell.

In addition to the warm weather, heavy rain is likely for much of the East. The warm, moist air being drawn northward from the Gulf of Mexico will be deposited up and down the East Coast later Sunday into Monday, and early Tuesday for parts of New England. Rainfall totals of 1-2 inches will be common, with some places possibly picking up 3 inches or more, especially in parts of eastern New England. While this will help put another significant dent in the long term drought that the region is experiencing, too much rain at once will likely lead to flooding in some areas.

Heavy rain is likely across the East Coast Monday into Tuesday. Image provided by Weathermodels.com

While all of this is going on ahead of the storm, a different scenario will be evolving on the storm’s back side. Colder air flowing southward from Canada will clash with the warm air, resulting in snow across parts of the Great Lakes and the Appalachians. The snow will be accompanied by gusty winds, lowering visibility in many locations, resulting in very hazardous driving conditions. While the snow won’t be exceptionally heavy, many places could receive upwards of 4-8 inches by the time everything winds down. Across the higher elevations of the Appalachians, even into the southern Appalachians, some heavier amounts are possible as well. As the systems gets caught under an upper-level low pressure system in southeastern Canada, it may produce some lake-effect snow into mid-week downwind of Lakes Erie and Ontario.

Accumulating snow is expected behind the storm system. Image provided by Pivotal Weather.

Once this system pulls away, things will quiet down across the East for a few days, but there are signs that another system could impact parts of the East next weekend.