Heavy Rain/Snow

Better Find Those Shovels

We warned you yesterday, and now it’s just about here. The first winter storm of the season, coincidentally falling on the first day of meteorological winter.

Low pressure is moving into the Great Lakes this afternoon while a secondary area of low pressure is starting to develop across the Delmarva Peninsula This secondary low will move northeastward tonight, then meander around south of Long Island, before drifting eastward on Monday. This will spread snow into the region later this afternoon and evening. Snow may fall moderate to heavy at times during the evening and into the first part of the overnight. As warmer air moves in aloft and at the surface, a change to sleet and then rain is expected along the coast, pushing inland as the night moves on. There’s still a bit of a question as to how far inland that changeover occurs. Right now, our best estimate is somewhere around the Massachusetts/New Hampshire border, give or take 10 miles.

Winter Storm Warnings and Winter Weather Advisories are in effect for much of the Northeast. Image provided by Pivotal Weather.

Precipitation should lighten up considerably toward daybreak as the low moves southeast of New England. We’ll still have occasional snow showers with some drizzle or freezing drizzle as the intensity lightens up, with only light accumulations during the day , mainly north and west of I-95. If you’re south and east of I-95, these will be mostly rain showers, as temperatures will likely be in the upper 30s or 40s, thanks to a coastal front.

The ECMWF model is fairly similar to our thinking for how the storm progresses. Loop provided by Pivotal Weather.

As the low moves east of Cape Cod on Monday, an upper-level low pressure system will move overhead, pulling the system northward into the Gulf of Maine, where it will start to intensify and also slow down. This will result in another period of steady snow Monday night into midday Tuesday. There will likely be a band of heavier snow that sets up on the backside of this storm. Exactly where that band sets up is still a question. Several models want to keep moderate snow going to much of the day Tuesday across most of eastern Massachusetts and into the New Hampshire Seacoast and most of Maine. We’re still not convinced that will happen. Right now, we think it’s more likely that band stays just offshore, clipping the Seacoast and the Eastern Massachusetts coastline. If we need to make changes to this part of the forecast, we’ll do so in our Weekly Outlook early Monday morning.

Again, the big question – how much snow can we expect? Our thinking isn’t very different than yesterday:

Cape Cod: 1-2″ (mainly on Tuesday)
Southeastern MA: 2-5″ (1-2″ Sunday night, another 1-3″ Tuesday)
I-95 corridor (Boston/Providence): 3-6″ (1-2″ Sunday evening, 2-4″ Monday night/Tuesday) The farther away from the coast, the higher the amounts.
North Shore/MetroWest: 4-8″ (3-5″ Sunday night, 1-3″ Monday night/Tuesday) The farther away from the coast, the higher the amounts.
Merrimack Valley: 6-12″ (4-8″ Sunday night, 2-4″ Monday night/Tuesday)
Central and Southern NH: 8-12″ (6-10″ Sunday night, 1-2″ Monday night/Tuesday)
NH Seacoast: 10-15″ (6-9″ Sunday night, 3-6″ Monday night/Tuesday)

Once again, the GFS Ensemble Mean is closest to our thinking with respect to snowfall totals. Image provided by WeatherBell.

The good news is that the rest of the week looks storm-free. It’ll be chilly (it is December after all), but no more snowstorms for now. Don’t expect that to continue for the rest of the month.

Heavy Rain/Snow

Time's Up, Winter is Arriving

We made it through November with just a few flakes, but your luck has run out. Mother Nature has decided to start December with a bang. We’ve got a very complicated storm coming, and for most of us, it’ll include snow, potentially a lot of it.

Winter Storm Watches and Warnings have already been posted for parts of the Northeast. Image provided by Pivotal Weather.

Today is a sunny albeit chilly day thanks to high pressure moving into southeastern Canada. As that high slides into Quebec, our sunny, chilly day will become a clear and cold night. Meanwhile the storm that’s been slamming the Rockies and Plains states for the past few days will head towards the Midwest. Normally, that would be good, as storms heading in that direction will move up the St. Lawrence Valley, keeping us mild with some rain. That’s not the case this time.

A secondary area of low pressure will develop off the Mid-Atlantic coastline on Sunday, and slowly drift south of Long Island. This will spread snow into the region during the mid/late afternoon hours on Sunday. Snow may fall moderate to heavy at times during the evening and into the first part of the overnight. As warmer air moves in aloft and at the surface, a change to sleet and then rain is expected along the coast, pushing inland as the night moves on. Precipitation should lighten up considerably toward daybreak as the low moves southeast of New England. So, that’s it, right? A quick 12-hour burst of snow and/or slop and we’re all done, right? Nope.

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

We’ll have some occasional flurries, drizzle, and freezing drizzle during the day on Monday as the system slowly moves out. At the same time, an upper-level low will move into the Northeast, spawning another system south of Long Island. This will bring colder air back into the region, with another period of steady snow Monday night into Tuesday morning, with everything winding towards daybreak Tuesday.

Now, there are several things that are still in doubt, that could have a significant impact on the forecast. First and foremost – the change to sleet and/or rain Sunday night. How quickly does the changeover happen and how far inland does it get? There’s at least one model that shows the change to sleet happening quickly and as far inland as southern New Hampshire, with a prolonged period of sleet for much of the evening and overnight. This is a detail that we’ll hopefully have a better handle on in the next 12-24 hours. Second problem – the second batch of snow Monday night. This is not set in stone either, and if it does occur, we’re still not sure exactly where that band sets up or how heavy it will be.

So, having said that, how much do we expect? Keep in mind, this is preliminary, and we will almost certainly update it again before the snow starts Sunday afternoon:

Cape Cod: 1″ or less, mainly with the batch Monday night:
Southeastern MA: 2-4″ (1-2″ Sunday afternoon, another 1-2″ Monday night)
I-95 corridor (Boston/Providence): 3-5″ (1-3″ Sunday afternoon/evening, 1-2″ Monday night)
North Shore/MetroWest: 4-7″ (3-5″ Sunday afternoon/night, 1-2″ Monday night)
Merrimack Valley: 6-10″ (4-8″ Sunday afternoon/night, 1-2″ Monday night)
Southern NH/NH Seacoast: 8-12″ (6-10″ Sunday afternoon/night, 1-2″ Monday night)
Central NH: 10-15″ (Mostly Sunday night into midday Monday)

The GFS Ensemble Mean is probably closest to our thinking at the moment. Image provided by WeatherBell.

Obviously, we’re staying very conservative with that 2nd batch, and we’re hoping to have better clarity on that with the next few model runs. We’ll update again tomorrow.

Extreme Temperatures, Heavy Rain/Snow, Winter Weather

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.

Heavy Rain/Snow, Tropical Weather

Trouble Brewing in the Gulf

It’s been a fairly slow start to hurricane season in the Atlantic, which is fairly normal, but things are starting to heat up in the Gulf of Mexico.

A disturbance dropped southward from the Tennessee Valley over the weekend, moving into the Gulf of Mexico on Tuesday. With plenty of warm water and only a little wind shear, the system is starting to get organized this afternoon, and could become a tropical depression later today or on Thursday.

Thunderstorm activity is getting more organized in the northern Gulf of Mexico this afternoon. Loop provided by NOAA.

As of 2pm Wednesday, the system was centered about 155 miles east-southeast of the mouth of the Mississippi River, moving toward the west-southwest at 8 mph. It is producing sustained winds of 30 mph, with some higher gusts. Steady strengthening is expected for the next few days. A Tropical Storm Watch has been posted from the Mouth of the Mississippi River to Morgan City, Louisiana. A Storm Surge Watch has also been posted from Pearl River to Morgan City.

Forecast tracks for Potential Tropical Cyclone Two from various forecast models. Image provided by WeatherBell.

The forecast models are fairly unanimous that the system will continue westward for the next 36-48 hours, but after that point things become unclear. A turn toward the northwest and eventually north is expected as an upper-level trough moves into the Great Plains, but when that turn occurs has a very significant impact on the system. A quicker turn means that the storm spends less time over the warm waters of the Gulf, and thus has less time to strengthen. A later turn means the opposite, more time over water, more time to strengthen, and the greater likelihood of it becoming a hurricane. Intensity forecasts are notoriously poor to begin with, and this system is no different. Very few models are predicting the system to reach hurricane strength, but the National Hurricane Center’s official forecast does call for the system to become a hurricane before landfall. As we mentioned already, the eventual track of the system will play a large part in determining this.

Intensity forecasts from various models for Potential Tropical Cyclone Two. Image provided by the University of Wisconsin.

Storm surge is a danger with any storm system, and this one is no different. Storm surge of 2-4 feet is likely near where the center makes landfall. Since much of southern Louisiana is already low-lying, this could result in flooding for much of the region. Wind damage will also be a concern across the region, which again will be dependent on the strength of the system. Winds will pick up Friday night across portions of Louisiana and possibly eastern Texas, with landfall most likely on Saturday right now, but this is obviously subject to change.

Rainfall forecast for the Gulf Coast for the next 6 days. Image provided by Weathermodels.com

By far, the biggest threat with this system will be rainfall. Tropical systems produce copious amounts of rainfall, and this one will be no different. Rainfall totals of 6 to 12 inches are expected across parts of the Gulf Coast, with some amounts to 20 inches possible. This would produce widespread flooding across the region, but in this case, it will just exacerbate existing flooding problems. The Mississippi River remains above flood stage across the region, and this will only worsen the flooding. On top of that, thunderstorms dropped up to 10 inches of rain on parts of New Orleans Wednesday morning, and that’s before the precipitation from the system even reaches the area. The Mississippi River is expected to crest in New Orleans at a level of 20 feet, which is also the same height that the levee system protects the city to. Obviously this will bear watching. Upstream, the River has been above “Major Flood” stage in Baton Rouge since February 26. It’s not likely to drop below flood stage until at least some time in August, if then.

River forecast for the Mississippi River at New Orleans. Record flooding is not expected, but the levee system will likely be tested once again. Image provided by NOAA.

Elsewhere, the Atlantic remains quiet, with no other systems expected to develop in the next week or so.

Heavy Rain/Snow, Weekly Outlook

Weekly Outlook: April 22-28, 2019

Did you enjoy the sunshine and warm temperatures at the end of the past week? Good, because you probably won’t get much of that this week. This week looks rather wet at times. The whole week won’t be wet, but there will be a few days that are quite damp.

We start the week off with some fog this morning, especially along the south coast, since we have plenty of moisture in the air. A weak system will pass offshore today, and it will bring in a period of rain and showers, mainly across eastern New England. Some of this rain will be locally heavy, and thanks to northeast winds off the still-cool Atlantic, temperatures will be cooler than the past few days. The rain may linger into Tuesday morning before the system pulls away. Some sunny breaks may develop in the afternoon, but they won’t last long. Another cold front quickly approaches for Tuesday night into Wednesday morning with more showers.

Some of the rain today into early Tuesday could be heavy across eastern New England. Keep that umbrella handy. Image provided by WeatherBell.

High pressure builds in for later Wednesday into Thursday with sunshine and seasonable temperatures, but this too will only be temporary. The next system approaches on Friday, with, you guessed it, more rain, but it’ll be generally light. High pressure returns for Saturday with some sunshine, but again, not for long. Yet another system will move in for Sunday with another round of rain, and there’s a chance that this could be heavy too. We’ll keep an eye on that as the week goes along, but don;t go cancelling any plans for next weekend just yet.

Rainfall has actually well below normal over the last couple of months across much of the Northeast, so we really need this week’s rain. Image provided by the Northeast Regional Climate Center

Monday: Fog burns off early, then a few sunny breaks are possible before clouds return, with rain likely during the afternoon. Becoming breezy during the afternoon, especially along the coast. High 57-64, but turning cooler in the afternoon along the coast.

Monday night: Periods of rain and showers, possible heavy at times. Low 45-52.

Tuesday: A few lingering showers in the morning, otherwise cloudy with some sunny breaks in the afternoon. High 51-58, except 59-66 north and west of I-495.

Tuesday night: Cloudy with scattered showers. Low 41-48.

Wednesday: Showers ending early, then skies become partly to mostly sunny and breezy in the afternoon. High 60-67.

Thursday: Mostly sunny for much of the day, clouds start to filter back in during the afternoon. High 59-66.

Friday: Mostly cloudy with showers likely. High 54-61.

Saturday: Sunshine to start, clouds come back in the afternoon, breezy. High 54-61.

Sunday: Mostly cloudy with a chance of rain. High 55-62.

Heavy Rain/Snow, Winter Weather

Sunday Night Special or Monday Morning Madness?

As promised, the second storm in our one-two punch is heading this way. While most of the snow is expected while you’re asleep Sunday night, it could have a big impact on your Monday morning commute.

Winter Storm Warnings and Winter Weather Advisories are in effect for most of the Northeast as of Sunday morning. Image provided by Pivotal Weather.

High pressure is hanging on this morning, providing us with sunshine, but clouds will quickly move in this afternoon as low pressure starts to move towards the Mid-Atlantic coastline, passing south of New England Monday morning. This storm will be a bit stronger than the one we had yesterday, and also have a little more moisture to work with, but will be moving fairly quickly, limiting the amount of time it spends in the region. One thing working in its favor is that most of the snow will fall at night. We’re at the time of year where the sun angle is high enough that snowfall during the daytime has a hard time sticking on pavement. At night, that’s not an issue.

The high-resolution NAM model shows the snow moving in this evening, becoming heavy overnight, and ending in the morning, with any rain confined to the south coast. Loop provided by Tropical Tidbits.

Snow will move in this evening, likely in the 7-10pm time frame, and will continue through the overnight hours. It may be heavy at times, especially between about 1 and 5am. A change to rain is expected for Cape Cod and the South Coast, but likely won’t advance past Route 44. Everything should wind down and end around 6-8am. That’s also the time of the morning commute. Road crews should have plenty of time to work on getting the roads cleared, but given past experience, and that people will likely leave early since it’ll still be snowing, we expect many roads to still be in awful shape. Give your self a lot of extra time in the morning. We also expect many school districts to cancel classes for Monday.

Snowfall is running about 10-20 inches below normal across the area this winter. Image provided by the Northeast Regional Climate Center.

It’s been a down year for snowfall, running 10-20 inches below normal across the area, but this storm will put a dent in those departure numbers. How much are we looking at?

Cape Cod/South Coast/Southern RI: 2-5″
The rest of the region: 4-8″ with isolated 10″ totals possible, especially from northern RI into the South Shore.

The high-resolution NAM has had a great winter for snowfall predictions, and we’re not straying from it again. Image provided by WeatherBell.

Things look to quiet down and get colder behind this storm, but a pattern change to milder weather could be coming as we head towards mid-March. We’ll have more details on at least the next week in our Weekly Outlook early Monday morning.

Heavy Rain/Snow, Winter Weather

Not One, But Two Storms on the Way

Back in our Weekly Outlook on Monday, we warned you that even though Meteorological Winter ends on February 28, that March can still be a wintry month. Well, today is March 1, and we’re looking at two snowstorms in the first four days of the month.

You can see that this is a fairly fast-moving storm. In by daybreak Saturday, out before dinnertime. Loop provided by Tropical Tidbits.

Technically, there’s actually 3 storms, as the first one is passing south of the region this morning. It brought in some clouds, and a few stray flakes across southeastern Massachusetts, but otherwise, had little impact on us. The first storm we need to pay attention to is moving across the central Appalachians this afternoon. It will move off the Mid-Atlantic coast tonight, then pass south of New England on Saturday. A few days ago, it looked like this storm would pass harmlessly to our south while a a system to the north brought in some snow or rain later on Saturday. Well, this storm became the more dominant of the two, and will pass closer to us than originally thought.

Snow will develop Saturday morning, maybe before daybreak south of Boston. It may even start as some sleet or rain across Cape Cod before changing to snow It will snow steadily during the morning hours, and then taper off and end during the afternoon, possibly lingering along the coast until evening. Despite the hype from some of the media, this will not be a big storm. Oh sure, it’ll be disruptive to your Saturday morning/afternoon plans, but it’s not a major storm.

So, the big question – how much?

Central NH/Southern ME (Concord/Portland) – Less than 1″
Southern NH/Seacoast/Cape Cod (Manchester/Nashua/Portsmouth) – 1-2″
Merrimack Valley – 2-4″
Metro Boston/MetroWest/Southeastern MA/ Rhode Island – 3-6″

Would be we shocked if a few spots, especially south of Boston, pick up 7 or 8 inches? Nope, not at all. This won’t be the fluffy snow we had a few days ago, so it won’t pile up as quickly.

We’ve stuck with the high-resolution NAM for most of the winter and it’s served us well, so we’re going to do it again. Image provided by Weathermodels.com

OK, so the snow ends Saturday afternoon/evening, and we’re all set, right? Nope – the next storm, follows fairly quickly for Sunday night and Monday. This one looks a little strong, and will pass a little closer. This will allow for the rain/snow line to penetrate a little farther into southeastern Massachusetts. However, with it being a stronger storm, it will have more moisture to work with, and that means more snow. There’s still many details that need to be worked out, and some things will depend on what the first storm does, so we’re not going to go into too much detail yet. We’ll have another blog post Sunday morning focused on that storm. But, there are several models showing the potential for up to, or even more than a foot of snow in spots from that storm.

The NAM model indicates that we could get a pretty good wallop early Monday. We’ll see if things stay that way over the next day or two. Image provided by Pivotal Weather.

After that storm goes by, it looks cold and dry for a few days. But let’s take it one storm at a time for now. Look for an update from us Sunday morning.