A Winter Storm Warning has been issued for New York City from 4am to 6pm Tuesday. Heavy snow and gusty winds are expected, with snowfall totals of 4 to 8 inches likely and locally higher amounts possible.
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Good morning! It’s been very active since the first week of March, with high-latitude blocking and anomalously cold air resulting in late season snowstorms for the Northeast states. April 2018 will wind up being one of the snowiest for many of the local climatology sites. However, it appears that we might be getting a break (finally) with the next few storm systems this weekend and early next week developing over the Eastern US. Read more
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.
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 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.
Good Evening Folks!
Well the close-call we warned you about on Monday has trended much closer to the coast over the past 48 hours, and looks to deliver the first light to moderate snowfall for many locations long the I-95 corridor! The setup for this storm has been a cold one, as a weak area of high pressure attempted to build over the Mid Atlantic states this afternoon. This area of high pressure has brought a more substantive portion of the Arctic airmass that lies just to our north, and this could certainly be felt today as the air had more of a “bite” to it. This Arctic air is also noticeably more dry than the previous stale airmass that has been in place, and will play a role in the snowfall forecast for tomorrow. Regardless, today’s highs were a bit colder than the past few days due to the reinforcement of the colder air and some mid to high level clouds streaming in overhead. The vast majority of the Northeast saw highs in the lower to middle 30’s, with middle to upper 30’s closer to New York and Philadelphia. This is just below normal for this time of year, and should be the norm for the next couple of days.
As we head into the evening hours, skies should remain mostly cloudy as more mid to low level moisture streams in thanks to a stout mid level jet transporting rich tropical moisture northward. As I mentioned earlier, there is a good amount of dry air in the mid to lower levels of the atmosphere, this should hold off the snow until the very early morning hours of Saturday. Locations farther south in portions of New Jersey may see an earlier start time due to more available moisture. In fact, Cape May New Jersey is currently seeing moderate snow, but this may be due to a moist marine airmass in that area. Overall, expect the mostly cloudy conditions to continue overnight, with lows likely dropping into the upper 20’s and lower 30”s across much of the New York city area. There is the possibility that the dry air will not be able to hold on for as long as the models expect, and portions of New Jersey, Maryland, Delaware and Pennsylvania could see some light snow before sunrise. Only light accumulations around a trace to two inches would be expected if this were to occur.
This evenings last-light visible satellite imagery, surface observations, and regional radar showing precipitation starting to work north into the Northeast.
Moderate Snowstorm Likely Saturday
The massive area of tropical moisture that we talked about back on Wednesday has certainly left its impact across the south over the past 36 hours, with snow being reported in all of the Gulf Coast states except for Florida. This system is being aided by a very strong and anomalous upper level jet streak overhead, which is working to promote the development of intense precipitation over the southeastern states. This system is not the only player for our storm tomorrow, as we have also been tracking an energetic piece of energy diving down from the far northern regions of Canada. As this system continues to move south and into the Great Lakes region, it will begin to interact with the system over the southeast and begin to create a favorable environment for the development of a coastal low to form just off the southeast coast. As this low continues to take shape and the two systems begin to interact further, we should see the bulk of the precipitation begin to move north and expand quite a bit over the Northeast by the early tomorrow morning. This expansion of the precipitation was something that was not well-handled by the models a couple days ago, and is likely to due to the very strong upper level jet streak aiding to the development of precipitation over the area. Snow should start from south to north tomorrow morning, and eventually making its way into the NYC area by 11am or so.
This evenings latest RPM model showing the potential evolution of tomorrows snowstorm across the Mid Atlantic and Northeastern states
We may see a period tomorrow morning where the radar looks to have snow over certain locations, but nothing is actually falling at the surface. This is due to the dry air in the mid to low levels of the atmosphere that causes snow to evaporate before it reaches the ground, but the radar beam still detects it when its far above the ground. This dry air will likely give way once the coastal low begins to intensify off of the Carolinas late tomorrow morning and into the afternoon hours. Expect the snow to start off rather light during the onset, but transition to a more steady rate for the duration of the storm. Portions of eastern New Jersey, southern New York, Long Island and Connecticut may see a few hours of heavy snow, with rates possibly nearing .5″-1″ an hour. Snow should continue through the late afternoon hours and into the evening, before tapering off from southwest to northeast during the early morning hours on Sunday.
As of right now, we are expecting a large swath of accumulating snow totals around the 3-6″ range from southeastern Pennsylvania, through most of New Jersey, and into New England. There may be localized amounts greater than six inches, but this may be confined to southern and eastern portions of the area where heavier snow bands may set up. Road conditions will likely be quite messy tomorrow as the snow is likely to create slippery conditions as it begins to ramp up in intensity. Travel may become hazardous during the afternoon hours during the peak of the storm, so it may be a good day to stay inside and get some work done and stay off the roads unless necessary. We will have updates on this storm after this evenings model runs come in as well as throughout the day tomorrow!
Storm Total Snowfall Forecast Map
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Have a great evening!
-Steve Copertino