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Sunday Briefing: Warmer east, snow in Plains, changes continue

Good afternoon, everyone! Much-awaited warm air has finally moved into the Eastern United States, on the heels of a prolonged period of cold. Temperatures today are running well above normal across a widespread area. Meanwhile, a deep trough and associated disturbance moving through the Rockies will eject northward into the Plains States later tonight into Monday, leading to the potential for a significant snowstorm in the Northern Plains.

The National Weather Service in Minneapolis, MN is forecasting a significant snowfall – but the gradient in snowfall totals is expected to be quite sharp. Snowfall totals could be very high underneath areas where impressive banding occurs, but could be much lower outside of those heavy snow bands. A very tough forecast! We explain a bit in our video below. Meanwhile, warm air will surge into the Eastern United States on Monday ahead of the system.

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Friday Briefing: Warmer times East, winter storm looms in Plains

Good morning and Happy Friday! We’re excited to introduce our daily briefing posts. Think of these as your “go-to” posts for weather information in the morning, whether you’re sipping a coffee or sitting on the train. Or both. We’ll lay out the important weather information with links and details on what’s ahead. More technical posts will follow throughout the day – but these will be the first checkpoint to see what’s going on.

So here we are! It has been a long and hard stretch of cold weather in the Northeast States. In fact, January is running well below normal in terms of temperature essentially from the Great Plains to the Northeast US Coast. That’s all about to change – big time changes in the Pacific Ocean will lead to changes in how the atmosphere is behaving across the United States. The storm track will shift west, and a ridge will build over the East. The result? Warmer temperatures for the East Coast and a pattern that will become inherently less wintry.

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Morning Snow Winds Down This Afternoon

Good morning! An inverted trough extending from low pressure offshore has resulted in bands of snow and rain across parts of the Northeast to start the day.  The majority of steady snow so far today has been situated over parts of Northern NJ and the Lower Hudson Valley into Southern New England, where the airmass remains colder and more supportive of precipitation. Closer to the coast, enough warm air from east-southeast winds off the ocean has lead to mainly light rain with some snow mixing in at times.

As low pressure moves further east off the Northeast coast and begins to deepen, it will drag colder air in behind it via northerly winds. Precipitation may end as a period of snow for coastal areas with some light accumulations under 2″. In fact, this is occurring already as of 8am over much of the NYC Metro Area. Any accumulations will likely be relegated to colder surfaces as temperatures remain above freezing.

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Snowstorm expected tonight across interior Northeast, less near coast

In the middle of a winter that seems to continually overproduce at the final buzzer comes another storm system, expected to develop late tonight into early Wednesday morning, that is expected to bring moderate snowfall to much of the Northeast states. It is really quite remarkable how many storm systems have trended more wintry in the final moments during the first half of this meteorological winter, and this storms system will be no exception. Occurring during a pattern transition, with warmer air moving in to the Northeast, it will feature challenges in terms of precipitation type.

A weak low pressure system is already in the process of developing off the Southeast US coast this morning. This low pressure area is mainly associated with an offshore baroclinic zone, or temperature gradient, near the Outer Banks of the Carolinas. Increased precipitable water values are noted on observations and forecast soundings, and models suggest this low pressure area will gradually organize later today.

Meanwhile, a deep trough will dig over the Central United States and is expected to amplify through the Mississippi Valley. As it turns towards the coast, and vorticity advection occurs near the coast, lift in the atmosphere will increase along the baroclinic zone and the low pressure system will deepen while heading north/northeastwards towards the Long Island coast. Precipitation is expected to develop to the west of the low pressure, near a frontal boundary, across the Northeast states later tonight.

Upper-level trough digging and amplifying over Eastern US. But the trough remains positively-tilted and more progressive.

The deep trough amplifying over the  Eastern US. But the trough remains positively-tilted, resulting in a more progressive storm system on Wednesday

Initial precipitation will be light, but steady, across parts of Pennsylvania and New England. But as the storm system gains some steam, banding is expected to develop across parts of New Jersey, Southeast New York and Connecticut and spread into New England. Without any prevalent high latitude blocking, the system will remain mostly progressive. But wintry precipitation amounts could still be significant in some areas, particularly across the interior.

One of the biggest forecast challenges tonight will be temperatures. While plenty of cold air exists aloft, forecast models are consistent in suggesting that the boundary layer will remain quite warm. The boundary layer is the low level atmospheric profile — where we live. And if it is warm enough, snowflakes can melt before they reach the ground. With an onshore flow (wind off the water) prior to the storm, models suggest this will be the case for much of Eastern New Jersey, Long Island, and Southeast Connecticut — mostly a cold rain.

Just inland, however, bands of snow are expected later tonight, and the potential exists for several inches of snow. While quick moving, models suggest enough dynamics for moderate snow in these bands, with quick accumulations of 3-6″ and possibly amounts higher than that in the highest elevations of Northwest NJ, Northeast PA, Southeast NY and New England. The winter storm is expected to be moderate impact in these locations, with a lighter impact event in NYC and even lighter along the coastal plain.

Expected Storm Total Snowfall from Tuesday Night/ Wednesday Afternoon

Expected Storm Total Snowfall from tonight through Wednesday Afternoon

The National Weather Service has, accordingly, issued Winter Weather Advisories for many locations. These create a good visual as to where the impacts are most likely and expected. In these regions, plan for winter weather tonight, including 3-6″ of snowfall, and leave extra time for travel through Wednesday morning when the event finally comes to a close.

The good news? Much warmer weather is anticipated over the coming days, with temperatures 10-15 degrees above average by this weekend! More details to come on that — we have a snowstorm to get through first.