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Winter returns with multiple threats next week

Temperatures will soar into the 50’s and 60’s during the day on Wednesday, as a strong low pressure system drives into the Great Lakes and eventually Southeast Canada.  This will, undoubtedly, leave many wondering if winter has taken its one and only stand with the blizzard at the end of January. Unbeknownst to most, however, is a large ridge driving into British Columbia and the Arctic Circle as we speak. This feature will help unload cold southward into Canada, and as a large ridge builds on the West Coast of the United States next week, multiple threats for winter weather will quickly make their way back into the forecast.

Friday morning light snow

This winter weather potential has flown under the radar (pun intended) as most have kept their eyes peeled on bigger storm potential next week. However, forecast models are still hinting at the potential for snow along the coast as a low pressure area develops on a frontal wave Friday morning. This frontal wave is the same cold front that will bring us rain and wind on Wednesday. Guidance has trended slower with the fronts movement, with a low pressure system developing along the front Friday.

GFS model showing a low pressure system scraping the area on Friday morning.

GFS model showing a low pressure system scraping the area on Friday morning.

Most notably, our area is in the right-entrance region of a 120kt 250mb jet streak. This supports the enhancement of precipitation to the northwest of the low pressure system along the front. A mid level shortwave trough takes on a negative tilt with positive vorticity advection near the Mid Atlantic Coast.

Most forecast models currently show this wave just scraping the area, with light precipitation over New York City, New Jersey, and Long Island. Colder temperatures aloft will support snow, but surface temperatures may remain slightly warmer and inhibit accumulations, especially if precipitation is light.

Forecasters are closely monitoring mesoscale developments and forecast model trends to see if this storm trends farther west. Such a trend would bring light accumulations into the picture for Friday morning.

Strong coastal storm swings seaward Monday

A strong ridge will building over West Coast early next week, with tremendous height rises from the West Coast into British Columbia. This will carve a longwave trough over the Eastern United States with several disturbances digging southward and amplifying near the coastal plain. The first southern stream disturbance ejects as early as Sunday into Monday, deepening rapidly off the East Coast.

GFS model showing a large piece of energy off the Southeast US coast this weekend and early next week.

GFS model showing a large piece of energy off the Southeast US coast this weekend and early next week.

This storm is likely to produce gale-force winds off the Southeast Coast, but forecast model guidance is currently in good agreement that this storm will stay well to the south and east of the region as it rapidly strengthens offshore and moves into the Atlantic Ocean.

Still, a tight pressure gradient between that storm system and a strong high pressure in Southeast Canada is expected. This will cause a persistent northeast flow that could result in minor coastal flooding during astronomical high tides on Sunday Night and Monday.

Nor’Easter, winter storm potential Tuesday and Midweek

The storm system of most interest to us is a “third wave” of energy, which ejects southeastward on the east side of a large West Coast ridge early next week. This storm system drives southeastward toward the Ohio Valley and eventually the Mid Atlantic States, with a low pressure center transferring from the Great Lakes region to a position off the Northeast Coast.

This is known more affectionately as a “Miller B” type storm system — as opposed to a “Miller A” where the low pressure center comes northward from the Gulf of Mexico or Southeast States (see: Blizzard of 2016). This system currently stands the best chance of the above three to impact the area with wintry precipitation. The details, however, remain very muted at this time, with a higher than normal amount of “moving parts” in the pattern causing model uncertainty.

European model ensemble mean showing a Nor'Easter south of Long Island early next week.

European model ensemble mean showing a Nor’Easter south of Long Island early next week.

Interestingly enough, one of the major uncertainties in regards to this event is the behavior of the storm system prior to it. That storm system’s exact track has implications on the location of the offshore baroclinic zone in the Western Atlantic. This thermal gradient often serves as a highway for low pressure area’s and can aid in their strengthening. But the storm system just a day or two prior can “drag” this thermal gradient farther offshore, meaning the mid week system won’t have as much room to amplify.

Ensemble guidance currently is strengthening a signal for a storm at this time period, but individual solutions have high variance. Understanding the interaction and wave spacing between these two features will be the first step in gaining confidence in any storm during the early to middle part of next week. From that point, we can begin to look deeper into the intricacies of the developing storm system — if it develops at all.

This article was written and compiled by Miguel Pierre and John Homenuk.

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