A Chilly Weekend is Coming, a Little Snow too?

By now, you’ve heard the TV meteorologists talking about how it’s going to snow, or you’ve read the headlines about an “historic May snowstorm” that’s coming. As usual, we at Storm HQ will avoid the hype and just give you the facts. Yes, there will be some snowflakes around here and no, it won’t be a big deal at all.

A cold front is moving across the Great Lakes this afternoon, and it move across our area tonight, with plenty of clouds and possibly a few showers. Behind that front, much colder air will start to move into the region. This is an anomalously cold airmass for early May, and in fact, is more representative of early March. That front is expected to stall out near the South Coast, and then a wave of low pressure will develop along the front and ride along it, crossing southern New England Friday night and early Saturday.

The ECMWF model shows the progression of the system for Friday into Saturday. Loop provided by Pivotal Weather.

We’ll have some rain moving in Friday afternoon and evening, but as the sun sets and temperatures drop, some wet snow will start to mix in. The most likely spots for snow are in the hilly terrain from northern Rhode Island across Worcester County and into the Monadnocks of southwestern New Hampshire, as well as out in the Berkshires. However, we wouldn’t be surprised if there was some wet snow mixed in with the rain even into the suburbs of Boston.

As we mentioned with the last few storms, it’s awfully tough to get accumulating snow into early May for a variety of reasons. For one, the ground is fairly mild. Any accumulations will be mainly on grassy surfaces, as pavement temperatures are much too warm now. Secondly, temperatures may not even drop to freezing, but could stay in the middle to upper 30s. Third, the intensity of the precipitation will be key. Heavier precipitation will bring down colder air from aloft, resulting in the change to snow, whereas light precipitation will tend towards more rain.

As far as accumulations, as we said, we’re not expecting this to be a big deal for most of us. You may wake up Saturday morning, if you’re up early enough, to see a little bit of a coating on grassy surfaces, decks, and car roofs/windshields. As we mentioned, most of the accumulations will be confined to the hilly terrain, where a few inches could fall.

Snow is fairly rare once you get into May. Using data for Lowell, snow has been recorded 5 times during the month of May over the past 92 years, and measurable snow only twice.

5/11/1945 – Trace
5/1/1953 – Trace
5/10/1977 – 2.6″
5/6/1996 – Trace
5/18/2002 – 1.0″

The ECMWF model is closest to our thinking for snowfall with this storm. Image provided by WeatherBell.

The snow is only part of the story though, and in fact, a minor part. As the storm intensifies while pulling away on Saturday, gusty winds are expected across the area. West winds of 15-25 mph with gusts of 40-50 mph are expected, especially along the coast. At the same time, an upper-level low pressure area will be moving into the region, bringing in very cold weather. That upper low may trigger a few rain or snow showers in the afternoon, but the cold temperatures will be the story. High temperatures likely will stay in the 40s, which may set records for the lowest high temperatures for the date in many locations.

Record low high temperatures are possible across parts of the region on Saturday. Image provided by Weathermodels.com

The really cold weather will be short-lived, as we will start to moderate on Mother’s Day as high pressure builds in. However, if you’re hoping for some sustained warmth, it’s not coming anytime soon. There are some hints that we may get out of the pattern that’s kept us quite chilly for most of April and early May in another 10 days or so, but a “warm” pattern is still a ways off.

Temperature forecast for the next 45 days for Bedford, Massachusetts based on the 51 members of the ECMWF Ensemble forecast. Image provided by Weathermodels.com

The image above is the high and low temperature forecast for Bedford for the next 45 days, based on the ECMWF Ensemble, which has 51 separate members. The solid red and blue lines in the middle of each graph are the “normal” highs/lows for each day. The green dot is the average of the 51 members for each day (which is also represented numerically in the middle of the 2 charts), and the shaded gray area is the area that between 1/4 and 3/4 of the members fall. The horizontal blue lines above and below that are the extreme on each day. As you can see, this model is forecasting temperatures to remain well below normal through May 14-15. After that, temperatures generally average near or a little below normal until June 9. Granted, “normal” for those dates is upper 60s to near 70 for high temperatures, so it’ll be milder, but still a little cooler than we should be. Finally, we get to near or a little above normal for a sustained period around June 10. Now this is just one model, so take it with a grain of salt, but it’s done fairly well diagnosing the general details of our weather pattern for several weeks now. There is hope that you can finally take your summer clothes out of storage, perhaps as early as next weekend.

Messy Tuesday, Frigid Thursday

The Winter Solstice is Saturday, but winter will certainly make it’s presence felt over the next few days.

The low pressure system that produced severe weather across the South on Monday will head northeastward, impacting our area on Tuesday. The storm will be moving fairly quickly, and it doesn’t have a lot of cold air to work with, so we’re not expecting a big snowstorm. That doesn’t mean it won’t cause any problems.

Winter Weather Advisories are in effect for most of the region. Image provided by Pivotal Weather.

Snow will develop around midnight across parts of Connecticut and Southern Rhode Island, gradually spreading northward across the rest of the region before daybreak. The snow should quickly change to rain after daybreak across the South Coast and Cape Cod. As warmer air moves in aloft, a change to sleet and freezing rain will start to take place across the interior, with plain rain along the coast as milder air moves in off the still relatively mild ocean. Right now, it looks like the mixing may get as far north as the Merrimack Valley during the afternoon. North of there, precipitation should stay all snow. The precipitation will lighten up during the afternoon, but won’t completely end until the evening or first part of the overnight.

The morning and evening commute will both be impacted by this storm, but the greater impacts will certainly be during the morning commute. Not only could icing be a problem, especially in parts of Connecticut and Rhode Island, we could be looking at a band of moderate to heavy snow along and south of the Mass Pike. With temperatures expected to drop below freezing at night, many roads could ice back up, so untreated surfaces could become slick, especially in areas that changed over to rain during the afternoon.

Icing could become a significant problem across parts of Connecticut and Rhode Island on Tuesday. Image provided by Pivotal Weather.

As for how much snow to expect, we haven’t changed our thinking much from our earlier forecast.

South Coast/Cape Cod: Less than 1″
Southeastern Massachusetts (including the I-95 corridor): 1-2″
MetroWest/North Shore: 1-3″
Merrimack Valley: 2-4″
Central + Southern New Hampshire/NH Seacoast: 3-6″

The High Resolution NAM model is probably closest to our expectations for snowfall. Image provided by WeatherBell.

Behind this system, we’ve got to pay attention to an arctic cold front that will move across the region late Wednesday. It could produce some snow showers or squalls as it moves through. These won’t impact everyone, but in places they do, visibility could rapidly drop, and a quick half an inch to an inch of snow could fall.

Wind chills will likely drop below zero across most of the area Wednesday night into Thursday morning. Image provided by Weathermodels,com

Behind that front, some of the coldest air so far this season will settle in for Thursday. Wind chills will be below zero during the morning hours, and actual temperatures may not make it out of the teens during the afternoon. Friday will see temperatures start to moderate a bit, but it will still remain quite chilly, even by December standards.

Weekly Outlook: December 9-15, 2019

Given a choice, would you prefer cold weather or warm weather? What about a choice between rain, snow, or dry weather? Well, you’re going to get ALL of these this week!

Temperatures could reach 60 across parts of the area on Tuesday. Image provided by WeatherBell.

We start the week with low pressure moving into the Great Lakes and then eventually up the St. Lawrence Valley. With low pressure passing to our north and west, we’ll be on the warm side, with rain expected, mainly in two waves. The first one will come in today, with rain developing this morning, and continuing into tonight, when it cold be locally heavy. The warm air should move in south of Boston fairly quickly, but it may take until tonight to get into the Merrimack Valley and southern New Hampshire.

Warm air comes in today, and is quickly pushed out by cold air late Tuesday into Wednesday. Loop provided by Weathermodels.com

We’ll have a bit of a lull tomorrow morning, but a cold front will approach later in the day, with rain coming back ahead of that front. We’ll still be on the mild side, that is until the front comes through. Temperatures will quickly drop behind the front late Tuesday and Tuesday night but the precipitation may linger, so we will likely see rain changing to snow Tuesday night.

The NAM model shows the progression of the storm with 2 waves of rain followed by some snow. Loop provided by Tropical Tidbits.

On Wednesday, a little disturbance will move across the region, bringing us some additional light snow, mainly in the morning. There’s still a bit of uncertainty with this, but plan on the morning commute being impacted. We’re probably only looking at a few inches, but all it really takes to screw up the morning commute is a few flakes at all. High pressure builds in late in the day and into Thursday with drier and much colder weather.

A few inches of snow could really mess up the Wednesday morning rush hour. Image provided by Pivotal Weather.

By Friday, temperatures start to moderate again as the high slides offshore. It’ll still be chilly (it is December after all), but not quite as cold as Thursday. The weekend looks even milder once again, but that’s because we’ll have another storm system passing to our north and west, so we’re looking at another round of rain, possibly heavy once again.

Saturday could end up quite mild once again, but wet as well. Image provided by WeatherBell.

Monday: Cloudy and becoming breezy with periods of rain and showers. High 49-56.

Monday night: Cloudy and breezy with rain likely, possibly heavy at times, tapering off late at night. Temperatures hold steady or possibly rise a few degrees.

Tuesday: Cloudy and breezy with showers redeveloping late in the day. High 53-60, but temperatures start to quickly drop from northwest to southeast during the afternoon.

Tuesday night: Cloudy with rain changing to snow during the evening. Low 26-33.

Wednesday: Cloudy with light snow ending around midday. Skies clear out at night. Temperatures hold steady or drop a few degrees during the day.

Thursday: Plenty of sunshine, but cold. High 24-31.

Friday: Becoming mostly cloudy. High 32-39.

Saturday: Cloudy, breezy, and milder with rain likely. High 46-53.

Sunday: Partly to mostly cloudy and breezy, chance for a few showers. High 42-49.

Weekly Outlook: November 11-17, 2019

Thank you to all that have served or continue to serve our nation. Image provided by the United States Army

Are you ready? Ready for Winter? It’s coming, and quickly. Better enjoy today, because after that, it’s going to get cold.

We start the week off with high pressure in control, but we’ll have plenty of clouds as a cold front begins to approach the region. That front will move through on Tuesday, with some rain likely ahead of it. Low pressure will develop along this front and move right across the region on Tuesday. Ahead of the low and the front, it will be somewhat mild, but once the front moves through in the afternoon, that’s when things start to happen.

NAM model forecast showing rain coming in ahead of the cold front, changing to snow before ending behind it. Loop provided by Tropical Tidbits.

Colder air comes surging in behind the front, and temperatures will quickly drop Tuesday afternoon. Rain will likely change over to sleet and snow from northwest to southeast. Now we’re not talking about a lot of snow, probably an inch or less in most spots, and mainly on grassy surfaces, but snow will be the least of the concerns. Gusty winds will help to dry out the roads, and ground temperatures remain fairly mild, but with temperatures dropping into the 20s by late Tuesday, we could see some ice developing, especially on elevated surfaces like bridges and overpasses. So, if you’re going to be out and about Tuesday evening or night, use caution.

While there might be a pretty good snowstorm up north, around here, we’re not expecting much. Image provided by Pivotal Weather.

We’ve covered the snow potential, and the potential for slick roads, but here’s the biggest issue we’ll be dealing with – it’s going to be cold. When we say “cold”, we mean “COLD”. As in, record low temperatures Wednesday morning across most of the region. As in wind chills (another phrase most of you don’t like) in the single numbers (Fahrenheit, not Celsius). Yeah, it’s going to feel like January Tuesday night into Wednesday. Oh yeah, we forgot to mention that Wednesday may see highs in the 20s to lower 30s.

Any location that is circled is likely to set a record low temperatures Wednesday morning. Yeah, it’s going to be cold. Image provided by Weathermodels.com

Winds will diminish for Thursday, but it will remain chilly. Temperatures should start to moderate a little on Friday as high pressure slides offshore. Of course, another cold front comes through Friday night and then we get cold again next weekend, but probably not quite as cold as Tuesday night and Wednesday. Temperatures will still be well below normal.

Wind chills will be in the single numbers when most of you wake up Wednesday morning. Image provided by WeatherBell.

Monday: Mostly cloudy with a few showers possible, mainly north of the Mass Pike. High 41-48 north and west of Boston, 49-56 south of Boston.

Monday night: Cloudy with showers developing late at night. Evening low 34-41 north and west of Boston, 42-49 south of Boston. Temperatures may rise after midnight

Tuesday: Cloudy and breezy with showers likely, changing to sleet and snow during the afternoon. Morning high 42-49 north and west of Boston, 50-57 south of Boston, then temperatures quickly drop in the afternoon.

GFS forecast for temperatures starting at midnight tonight and ending at 7am Wednesday. Loop provided by WeatherBell.

Tuesday night: Any lingering snow showers end in the evening, then clearing, breezy, and colder. Low 13-20.

Wednesday: Sunny, breezy, and cold. High 25-32.

Thursday: Intervals of clouds and sun, a few flurries are possible at night. High 34-41.

Friday: Sunshine to start, then clouds move in during the afternoon. High 43-50.

Saturday: Sunshine and some afternoon clouds. High 31-38.

Sunday: A mix of sun and clouds. High 37-44.

Boston May Need an Ark, Bismarck Needs a Plow

Two developing storm systems – one off the East Coast and one in Plains, will both wreak havoc in the next few days, but for very different reasons.

Two low pressure areas are developing off the East Coast early this morning. The northern system is the stronger of the two, but the southern one is being monitored by the National Hurricane Center. It has the potential to develop into a tropical depression or subtropical storm later today. Whether it does or not, these two low pressure areas will eventually merge and become a rather strong non-tropical system over the next 24 hours. There is very little in the way of steering currents right now, so the system will just meander around off the coast until Saturday.

Low pressure won’t be in a hurry to go anywhere off the East Coast for the next few days. Loop provided by Tropical Tidbits.

As the system drifts northward, it will produce gusty winds along the coast, especially in New England. Tides are astronomically low at the moment, but will be rising later this week, so coastal flooding, while not a major concern, will still be possible in some locations. A coastal flood watch has been issued for parts of Plymouth County, Cape Cod, and Martha’s Vineyard. Rough seas will also be a large concern for marine interests, with Storm Warnings now in effect offshore. However, the biggest concern and also the biggest question mark right now is heavy rainfall.

Wind gusts in excess of 50 mph are possible across much of Southern New England. Yeah, that blows. Image provided by WeatherBell.

While the storm will likely spread some heavy rainfall into New England, there is still plenty of uncertainty as to how far north the heavy rain gets, as well as how much rain actually falls. Some of the models are producing extremely heavy rainfall, with totals in excess of 10″ in southeastern Massachusetts! While we aren’t buying the extreme totals, the fact that most of the models are showing this potential means that some very heavy rain is likely, especially south of Boston, where a Flood Watch has been issued.

That’s a lot of water coming out of the sky over the next 3 days. Some models have even more than this! Image provided by WeatherBell.

Thanks to some dry weather over the past couple of months, we shouldn’t have to worry about any flash flooding, though downpours will result in ponding of water on roadways, and some locations normally prone to flooding in heavy rain will also have problems. However, since we’re expecting a prolonged period of heavy rain, flooding is still a possibility in some locations, other than the ones we just mentioned, especially some of the smaller streams and rivers. Strong winds will also start to take some of the leaves off of trees, which may clog up storm drains, resulting in some flooding as well.

Recent dryness means that flash flooding is not likely in New England with this storm. Image provided the the Northeast River Forecast Center.

While all this is taking place off the East Coast, some very cold air will settle into the Rockies and Plains states as low pressure starts to develop across the Central Plains. Record lows are likely to be set in numerous locations over the next few mornings across the region. This system will head north-northeastward while strengthening. The system isn’t expected to become that strong, but with a large high pressure area building in behind it, it will produce some strong winds. It will also draw warm and moist air northward from the Gulf of Mexico. As this air runs into the much colder air on the backside of the storm, the first significant snowstorm of the season is expected to develop across the Northern Plains.

Winter Storm Watches and warnings have been posted from parts of Idaho Montana, and Wyoming into parts of northern Nebraska and the Dakotas as well as northwestern Minnesota. across Idaho, Montana, and Wyoming, snowfall totals of 6-12 inches are possible, with some heavier amounts in the higher elevations. The biggest issues are expected across the Dakotas and northwestern Minnesota.

Wind gusts of 40-50 mph or more are expected across the Northern Plains. Image provided by WeatherBell.

The precipitation will start as rain across this area later today, but strong northerly winds will usher much colder weather in, changing the rain to snow from west to east on Thursday. Like its East Coast counterpart, this storm won’t move at a rapid pace, so snow, possibly heavy at times will continue across this area into early Saturday, with snow showers lingering into Sunday.

This storm also has some questions with it’s precipitation shield. While heavy snow is likely across a large area, how much falls and where the heaviest snow will fall is still a question. Right now, it looks like the heaviest snow will fall from central South Dakota into central and eastern North Dakota, but that still could change. As for amounts, many areas could see more than a foot, with totals in excess of 2 feet possible in some areas. The snow will be accompanied by winds gusting to 40-50 mph, resulting in blizzard conditions, especially late Thursday into Friday.

Welcome to winter! Snowfall totals of 1-2 feet or more are possible across the Dakotas. Image provided by Pivotal Weather.

While snow in October is not unusual across this region, snowfall amounts of this magnitude this early in the year are extraordinarily rare. In Grand Forks, ND, the largest October snowstorm on record occurred October 24-26, 2001, and it dropped 10.9″ on the city. In Fargo, ND, the largest October snowstorm on record is only 8.1″ on October 30-31, 1951. For Pierre, SD, the October snowstorm of record occurred October 30-31, 1943, and it only produce 7.2″ of snow. Current model forecasts are forecasting amounts that are 3-4 times the records. These model forecasts are likely too high, but it seems likely that many of these October records are going to be obliterated in the next few days. Hopefully, this is not a sign of what’s to come this winter.

Here Comes the Heat

Excessive Heat Warnings and Heat Advisories are in effect right through the weekend across much of the Northeast. Image provided by Pivotal Weather.

We warned you in our Weekly Outlook that it was coming, and it’s just about here – some brutal heat and humidity is expected for the next few days.

High pressure at the surface and aloft will be responsible for our heat and humidity through the weekend. Image provided by Tropical Tidbits.

Friday will start out with some lingering clouds and a little fog, but the sun will return and as winds shift into the southwest, so will the heat and humidity. Many locations will reach 90 on Friday, but not everyone. Dewpoints will get into the lower 70s, sending the heat index well into the 90s across the region. At night, with plenty of humidity around, temperatures likely won’t drop below the middle 70s across the region, making for an uncomfortable sleeping night if you don’t have air conditioning. This sets the stage for Saturday.

Saturday will likely be the hottest day we’ve had around here in several years. Add in the high humidity (dewpoints again in the lower to middle 70s), and well, it’ll be downright brutal outside. Since it will already be warm to start, with plenty of sunshine, temperatures will quickly jump in the morning, with many locations likely reaching 90 by lunchtime, but it won’t stop there. Temperatures will likely get into the upper 90s, with some spots, especially in the Merrimack Valley, possibly topping 100 degrees.

It’s going to be hot on Saturday. Really hot (by New England standards). Image provided by WeatherBell.

How rare is a 100-degree reading? Since the Merrimack Valley is the likeliest spot, here is some data for Lowell. In the 131 years of temperature records for Lowell, the city has topped 100 degrees just 35 times, or about once every four years. However, it’s actually been 8 years since Lowell hit 100, with a high of 102 on July 22, 2011. Before that, you have to go back to 2002, when it hit 101 on August 14, and 100 on July 3. So that’s just 3 times in the past 17 years. Skewing that average of once every 4 years is the fact that Lowell reached 100 5 times in 1911, 4 times in 1949, and 5 times in 1952. That’s 14 among those 3 years alone. July 22, 2011 was also the last time it reached 100 at Logan Airport in Boston, where they’ve only hit 100 25 times in 147 years of records.

With temperatures in the upper 90s (or higher), and dewpoints in the lower to middle 70s, that means that the heat index will be in the range of 105 to 110 degrees or higher during the hottest part of the day. If you have any plans to be outside, whether it be by the pool, at the beach, at the NASCAR activities in Loudon, or anywhere else, make sure you try to stay hydrated, and take plenty of breaks in the shade if you can.

Heat indices will likely be well over 100 across most of the region Saturday afternoon. Image provided by Weathermodels.com

Saturday night will be another uncomfortable night, with low temperatures only dropping into the middle to upper 70s. Some of the urban locations, like Boston, may not drop below 80. This leads in to another brutally hot and humid day on Sunday. Once again, most places will likely reach 90 by lunchtime and keep going. High temperatures will again get into the upper 90s across the area, with some 100-degree readings possible. Dewpoints will remain in the upper 60s to lower 70s, so we’re looking at heat indices in the 105 to 110 degree range once again.

Sunday looks to be another scorcher, but we’re not quite convinced it will be as hot as this model is showing. Image provided by WeatherBell.

By late Sunday, a cold front will start to approach, and it may produce some showers and thunderstorms during the evening and overnight. Behind it, much more seasonable air and lower humidity settles in for Monday. There may be a little relief in spots before that as well. Thunderstorm complexes in the Midwest will ride along the top of the upper-level ridge, as it typical in the summer. Right now, it looks like this may happen both late Friday and late Saturday. Unfortunately, it looks like these may fizzle before reaching the Northeast, and if they don’t, they will likely pass southwest of our area. So, we’re not holding out hope for these to help cool us off.

Long range forecasts show that some heat may return late next week into next weekend, but not nearly to the extent of what we’ll be dealing with for the next few days.

Weekly Outlook: March 4-10, 2019

The first full week of March is shaping up to be a wintry one, mainly in the temperature department, but a little in the precipitation department as well.

The snow will be ending across the region this morning as our storm system pulls away, with some clearing this afternoon. Temperatures may even get a tad mild, allowing for some melting to take place. However, we’re going to drop back below freezing tonight, so anything that melted with ice back up. If you’re heading out this evening, watch out for slippery conditions on untreated surfaces.

Temperatures could get into the middle to upper 30s this afternoon, allowing some of the fresh snow to melt. Image provided by WeatherBell.

After that, a rather cold airmass will settle into the region for Tuesday through Thursday. While temperatures won’t be as extreme as in the Plains states, we’re still looking at temperatures that are 10-20 degrees below normal, especially Wednesday and Thursday. A couple of upper-level disturbances will also be moving through the region, which may produce a few snow showers at times, especially Wednesday and Thursday.

Temperatures will be 10-20 degrees below normal during the middle of the week. Image provided by Weathermodels.com

By Friday, high pressure will move offshore and temperatures will start to moderate. That just means it won’t be quite as cold, but temperatures will still be below normal. The weekend is where things get complicated.

It looks like we’re going to have 2 systems impact the area, a weak one on Saturday, and a stronger one on Saturday. Given that these are both several days away, nothing is set in stone at this point. The first system passes south of New England on Saturday. There is at least one model that has it pass too far south to have any impact on us, but most bring it close enough to spread in some light precipitation. Right now, it looks likely mainly some light snow, but it could be some rain as well, especially along the south coast.

The stronger storm comes in on Sunday. This one looks like it will produce some rain across the area. However, some models are showing temperatures below freezing at the start, which means we’d be looking at yet another situation where we have snow to sleet or freezing rain inland and rain along the coast. Again, this is a week away, so trying to nail down details at this point is a futile exercise. Just be aware that next Sunday could be messy, especially north and west of Boston.

Daylight Saving Time starts at 2am Sunday. Sunset next Sunday evening will be at approximately 6:45pm. Image provided by the National Weather Service.

Monday: Snow (rain on the Cape) ending early, some sunny breaks develop in the afternoon. High 33-40.

Monday night: Becoming mostly clear. Low 9-16.

Tuesday: Morning sunshine, afternoon clouds, slight chance for a snow flurry. High 24-31.

Tuesday night: Clear to partly cloudy. Low 10-17.

Wednesday: A sunny start, then clouding up again, breezy. A snow shower is possible. High 19-26.

Thursday: Intervals of clouds and sunshine, with a few afternoon snow showers possible. High 20-27.

Friday: Plenty of clouds. Light snow or rain developing at night. High 28-35.

Saturday: Cloudy with some snow or rain showers possible in the morning. High 31-38.

Sunday: Cloudy with a chance of rain, possibly some snow or a wintry mix across the interior. High 34-41.

Weekly Outlook: January 28 – February 3, 2019

The winter of little snow rolls on this week, with just a little bit of snow and more cold weather. Don’t worry, it won’t last too long, and it could be a LOT worse.

The week starts off with high pressure building in, giving us sunshine and seasonably cold conditions. Clouds will start to move in during the evening as low pressure heads towards the Midwest. As this system moves across the Great Lakes on Tuesday, snow will develop across the region Tuesday afternoon. A secondary area of low pressure will develop across the Mid-Atlantic states during the afternoon. This will help bring milder air into the region, changing to snow to rain during the afternoon and evening hours. Whether or not this changeover makes it into southern and central NH is still a question mark. Either way, this doesn’t look like a big snow producer, with a few inches across central and southern NH, and an inch or less elsewhere.

This storm is not expected to be a big snow-producer across the area. Image provided by Pivotal Weather.

Once that secondary low pressure area moves past the area, colder air will quickly move back in, changing any rain back to snow before it ends towards daybreak. That’s not the end of the story though. We could see some sunshine develop in the afternoon, but an arctic front will move through late in the day. This front may produce some snow showers or squalls, which could impact the Wednesday evening commute, but they may hold off until a little later. These squalls may briefly lower visibility, and could drop a quick half inch or so, but the bigger story is what comes in behind the front.

Wind chills will be well below zero when most of you are heading out to work or school Thursday morning. Image provided by Weathermodels.com

Skies clear out Wednesday night as high pressure builds in, ushering in much colder air. While it won’t be quite as cold as last Monday when most of the area had high temperatures around 5 degrees, we’ll have more wind this time, so wind chills will be well below zero on Thursday. So, how could it be worse? When this airmass moves into the Northern Plains and Upper Midwest later Tuesday into Wednesday, temperatures will be a LOT colder. Across parts of the Dakotas and Minnesota, low temperatures will drop near or below -40 Thursday morning, with afternoon highs not reaching -30 in some areas. This is actual air temperature, not wind chill. So what will the wind chills be? How does -60 to -65 sound? We’re not quite sure why people voluntarily live in this area, but they do.

Yes, wind chills could be lower than -60 in parts of the Upper Midwest and Northern Plains Wednesday morning. That is beyond ridiculously cold to us. Image provided by Weathermodels.com

Getting back to our weather, Thursday night will be chilly, but we’ll start to moderate on Friday as high pressure shifts to the east. Oh, it’ll still be cold, just not as cold as Thursday. The gradual warmup will continue on Saturday as high pressure moves offshore and then a warm front moves through on Sunday with milder weather moving in.

Monday: Mostly sunny and chilly. High 24-31.

Monday night: Increasing clouds. Low 15-22.

Tuesday: Cloudy with light snow developing in the afternoon, quickly changing to rain south of Boston. High 30-37.

Tuesday night: Light snow likely across central and southern NH, changing to rain from the MA/NH border southward during the evening. Rain changes back to snow everywhere after midnight, ending towards daybreak. Temperatures may rise a bit through midnight, then drop back to 22-29 by daybreak.

Wednesday: Breezy with any snow showers ending early, then skies become partly to mostly sunny. Snow showers or squalls are possible in the evening. High 26-33, but temperatures will quickly plunge at night.

Thursday: Partly to mostly sunny, breezy, and much colder. High 7-14.

Friday: Sunshine and afternoon clouds, still cold. High 17-24.

Saturday: A mix of sun and clouds, still chilly. High 22-29.

Sunday: Partly sunny and milder. High 34-41.

Storm Update – Less Snow, More Problems

In our forecast yesterday, we told you that some of the biggest questions were the track of the storm system and related to that, how far north the change to sleet/freezing rain would take place. Well, we’ve got some more clarity on that now.

Some of you are already seeing some snow falling this afternoon, but this is not related to the storm. Some ocean-effect snow has pushed into Cape Cod and Plymouth County, and will continue to push inland this afternoon. This will be light, with less than an inch in most spots. The steadier snow will move in late this afternoon and evening from the west, reaching southern NH and the Merrimack Valley first, then the rest of Eastern Massachusetts and Rhode Island. It’s after midnight where the changes start to take place.

The NAM model shows the progression of the storm with the changeover to sleet. freezing rain, and plain rain gradually spreading northward early Sunday. Loop provided by Tropical Tidbits.

The storm system looks like it will track a bit farther north, passing very close to Boston on Sunday. This will not only allow milder air to move into most of southeastern Massachusetts, but the milder air aloft will also move much farther north than we had anticipated yesterday. Snow will fall heavy at times overnight, especially north of the Mass Pike, but as the warmer air starts to move in, we’ll see a change to sleet and eventually freezing rain move into the South Coast towards Midnight. A change to plain rain is likely before daybreak across southern Rhode Island and southeastern Massachusetts, as temperatures may break into the 40s Sunday morning. Some of the rain could be heavy, which may wash away most of the snow that does fall. Farther north, snow will gradually change to sleet and freezing rain north and west of Boston towards daybreak, with the changeover likely getting into southern NH as well. This will significantly cut down on snow amounts, but could make travel quite hazardous if there’s enough freezing rain.

The NAM model is forecasting up to 1/4 inch of freezing rain in parts of southern NH and the Merrimack Valley. Image provided by Pivotal Weather.

By midday, the storm passes by and moves offshore, with winds shifting into the north. This will bring much colder air back in, and rather quickly. Temperatures may get close to or a little above freezing during the morning from southern NH into the Merrimack Valley and the northern and western suburbs of Boston, but by afternoon they’ll quickly drop into the 20s during the afternoon and teens by evening. That will result in a flash freeze, and any untreated surfaces will quickly freeze up, resulting in very hazardous travel. It will also mean that anything you haven’t cleaned off of your car, driveway, sidewalk, etc. will quickly turn into cement. The bitterly cold air will continue to flow in, and temperatures on Monday may struggle to reach the lower teens, with wind chills below zero thanks to gusty northwest winds. These gusty winds may also produce some ocean effect snow across parts of Cape Cod, especially the Outer Cape.

The High Resolution NAM model shows the rollercaster that our temperatures will be on over the next couple of days. Loop provided by Weathermodels.com

So, how much snow are we expecting now? Here’s our current thinking:

Cape Cod/South Coast: 1-3 inches
Southeastern Massachusetts/I-95 corridor: 2-4 inches
MetroWest/North Shore: 3-5 inches
Merrimack Valley/NH Seacoast: 3-6 inches
Southern NH: 4-7 inches
Central NH/Southern Maine: 8-14 inches, with higher amounts the farther north you go.

While there isn’t any one model that matches our current thoughts on accumulations, the High Resolution NAM model is closest to our current thinking. Image provided by the College of DuPage.

Temperatures will slowly start to moderate on Tuesday, then another system may move in on Wednesday, but this one, believe it or not, may be mostly rain. We’ll see how that evolves over the next few days.

The Party’s Over – Here Comes the Snow

We haven’t had a decent-sized snowstorm around here since late November. Well, that is about to end, much to the dismay of most of you. We’ve got several different concerns with this system, so we’ll try and touch on all of them.

Winter Storm Watches and Warnings are in effect for most of the Northeast with a Coastal Flood Watch for parts of the Massachusetts coastline. Image provided by Pivotal Weather.

We’ll start with what’s going on now. High pressure is building into Quebec, and this will bring cold air into the region. Tonight will be chilly, with lows in the teens, maybe even some single numbers. Meanwhile, low pressure is moving out of the Southern Plains. This low will move towards the Appalachians on Saturday, then off the Mid-Atlantic coastline Saturday night. This brings us to forecast problem number 1. Where does the low track from there? This is a critical point, as it will help determine what type of precipitation falls across the area. Some models keep the storm offshore, south of the Cape and Islands, while others bring it right across southeastern New England. We’re thinking it tracks pretty close to the Islands, but stays just to the south. By Sunday, it moves into the Gulf of Maine, and takes all of the precipitation away.

As for the timing of that precipitation, there’s not much disagreement among the models. Snow should move in during the evening hours (7-9pm) from west to east, and end during the afternoon (3-5pm) on Sunday, except across Cape Cod and parts of southeastern Massachusetts, where it may linger into Sunday night. The heaviest precipitation will likely fall between about 11pm Saturday and 8am Sunday, so if you don’t have to be out then, we’d recommend that you stay where you are.

The High-Resolution NAM model shows the progression of the precipitation across the region. Blue is snow, orange is sleet, purple is freezing rain, and green/yellow is rain. Loop provided by Weathermodels.com

What type of precipitation is going to fall? Well, that is a BIG question, that is still in doubt for a large portion of the region. It should start as snow for everyone. It will likely change to rain across Cape Cod and the South Coast, and parts of southeastern Massachusetts. In between? That’s where things get really complicated. As we usually see during storms, we’re going to have a “coastal front” set up. Basically, the milder air from the ocean will push inland a bit. If you are south and east of this coastal front, temperatures will be near or just above freezing. If you are on the other side of the front, temperatures will be in the teens. Eventually, this front will collapse to the coast on Sunday, bringing the cold air in everywhere (more on that later). But the surface is only part of the equation. Warmer air will also move in aloft. How far inland it moves is something that that models disagree on right now. With warm air aloft and cold air at the surface, the precipitation will change to sleet or freezing rain, depending on how thick the layer of warm air is above the surface. Obviously, this will have a significant impact on snowfall amounts. Everything should go back to all snow Sunday afternoon as the coastal front collapses toward the coastline.

The high-resolution NAM model shows a well-defined coastal front setting up in the Merrimack Valley and the I-495 belt Sunday morning. Image provided by WeatherBell.

We’ve got more concerns than just what falls from the sky though. The full moon is Sunday night, which means that tides will be astronomically high. That is usually enough for some minor coastal flooding in a few spots. However, when you add in east to northeast winds of 15-25 mph and gusts to 40-50 mph (or more), then you get coastal flooding in a much wider area, possibly even some moderate flooding in the more vulnerable locations. This is mainly a concern for the high tide that occurs Sunday morning. The winds will also be a concern inland, as it will create blowing and drifting snow, making driving even more hazardous.

We mentioned earlier that the coastal front would collapse to the coastline during the afternoon, bringing cold air back in everywhere. As that cold air comes rushing in, we expect everything to quickly freeze up Sunday afternoon and evening. This will create black ice on the roads, but more importantly, any snow still on your driveway, cars, roads, etc, will quickly turn into cement. You’ll want to get outside and quickly clear everything off, because the longer you wait, the more difficult it will become. Temperatures will continue to drop Sunday night, and as high pressure builds in, skies will clear out, which may allow for viewing of the total lunar eclipse Sunday night. On Monday, temperatures won’t rise that much, with many places likely staying in the single numbers or lower teens. It will still be breezy, so wind chills may stay below zero all day long. Temperatures will start to moderate on Tuesday, but longer-range indications are that we are in a colder (and stormier) pattern now, so winter has finally arrived.

This is the forecast high temperatures for Monday based on the GFS model. It’s going to be cold. Image provided by Weathermodels.com

OK, finally, the part you’ve all been wondering – how much are we getting? As we’ve said, the amount of sleet and freezing rain will have a significant impact on snow accumulations, so we’re going to keep our ranges somewhat wide for now, and if need be, we’ll put out an update on Saturday.

Cape Cod: 2-4″
Southeastern Massachusetts/Southern Rhode Island: 3-6″
I-95 corridor (including Boston and Providence): 4-8″
MetroWest/North Shore: 6-12″
Merrimack Valley/NH Seacoast: 8-14″
Southern NH/Southern ME (Nashua/Manchester/Portland): 10-16″
Central NH (Concord): 12-18″

The NAM model is probably closest to our thinking right now, though some of these numbers may be a bit higher than our thoughts. Image provided by the College of DuPage.

If time allows, and/or there is a significant change in the forecast, we’ll update this on Saturday.