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Monday Briefing: Winter Storm in the Northeast Wednesday

Happy Monday! High pressure from the west, builds into the Northeast today, behind our departing storm system on Sunday. Mostly sunny skies and breezy conditions are expected.  Cold air advection with northwest winds behind a cold front early this morning will keep temperatures nearly steady in the mid-upper 30s most of the day. A tighter pressure gradient could cause winds to gust up 30 to 35 mph at times.

Skies will remain clear and winds diminish early tonight. Then some mid-high clouds will be increasing, as a weak upper-level disturbance approaches from the west. Overnight low temperatures will range from the upper teens to middle 20s in many areas. However, some of the Interior Valleys and Pine Barrens may drop into the lower to middle teens, with some radiational cooling occurring, before more clouds arrive.

Cloud cover will persist into Tuesday morning as the upper-level disturbance moves through. A few isolated-scattered snow showers are possible, especially over the Interior parts New York State and Pennsylvania. But moisture will be lacking with this disturbance. So these showers will likely be weakening after cross the mountains and any snow accumulations will be between a dusting to 1” with some slick spots also possible on roads, for the morning commute.

RGEM model showing snow showers over parts of Northeast Tuesday morning

RGEM model showing snow showers over parts of Northeast Tuesday morning

Skies clear for more sunshine by the afternoon hours on Tuesday. More southerly winds will help temperatures rise into the upper 30s to lower 40s for highs. Then clouds will be increasing again on Tuesday night, as next storm system approaches from the southwest. More cloud cover will likely keep temperatures from dropping below the upper 20s or lower 30s, over most areas.

Increasing warm-air advection and moisture ahead of this system will likely result in precipitation arriving from the southwest, during the morning to early afternoon hours. The airmass will still be cold enough for precipitation to being as snow in many areas of the Northeast. High pressure still to northeast may also result in tighter thermal gradient or stronger frontogenesis for a front-end moderate snowfall

However, overall the flow is still fast, with a lack of high-latitude blocking in the Atlantic. So high pressure will be departing to the northeast and low pressure with this storm system, will be taking a more inland track from over the Northern Mid-Atlantic into Southern New England. This setup will allow for some warmer air intrusion, in the lower to middle levels of the atmosphere, during the day on Wednesday, especially to the south and east of the low track.

3km NAM model showing snowfall much of Northeast for Wednesday

3km NAM model showing the winter storm producing snowfall, ice and rain over Northeast by early Wednesday afternoon

For the I-95 corridor major cities and further east, more marine influence with east-southeast winds will cause snow to quickly changeover to rain by the mid-late afternoon hours. Subsidence from high pressure may also result in precipitation holding back until the late morning or early afternoon hours. So light snow accumulations, between a coating to 2” appears mostly likely.  However, there is a lower chance, snow begins during early or mid-morning hours and with some areas receiving between 2” to 4” of snowfall.

Over the higher elevations of the Northeast, including Northwest New Jersey and Lower Hudson Valley, any changeover to rain is likely to take longer to occur, farther away from the warmer ocean influence. There is potential for snowfall totals around 4” or higher for these areas. There might also be a period of sleet and freezing rain in between the transition, as cold air tends to be slower to scour out in the lower-levels. Overall some travel delays and hazardous roads are likely, especially over the Interior Northeast on Wednesday.

The entire storm system begins leaving on Wednesday night. As colder air rushes in, any wintry mix or rain may change back to snow before ending. But little if any additional accumulations are expected. Then high pressure builds in, behind this storm system with more tranquil and seasonable cold weather again on Thursday and Friday. Stay tuned for another update later today or early this evening, as we fine tune snowfall totals and other forecast details for the winter storm in Northeast on Wednesday.

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