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The arctic air reservoir across the Midwest/Northeast U.S. this afternoon is set to be replenished over the next 2 days pulled southward by a developing storm off the Mid-Atlantic/Northeast coast. The developing storm will be quickly unusually intense due to the replenishing arctic chill across western North Atlantic SSTA averaging 1-3C warmer than normal.

Climate Impact Company is following the 12Z GMT ECMWF model. The ECMWF had this storm as much as 1 week ago, particularly the coastal Southeast U.S. event.  I was informed by a colleaue that a USAF RECON will fly into the developing storm off the Georgia Coast this evening. This storm is considered unusual due to the evolution over SSTA 1-3C warmer than normal. That warm signature should change substantially after this event as colder subsurface water is up-welled to the surface.

The warm SSTA is mentioned as this storm takes on subtropical characteristics east of the center while arctic air surges into the west and north side of the storm from Canada. ECMWF indicates a 951 MB low off Nantucket at 1PM EST tomorrow while high pressure over western Ontario is 1039 MB. Obvious implications are high wind likely past hurricane threshold in southeast Mass. and certainly just offshore. The forecast track is a little closer to the coast so enough warm air causes some rain mix into southeast Mass. to lower snowfall amounts.

Along and just west of that mix line we’re looking at a blizzard. Right now NOAA indicates a blizzard warning along the Massachusetts/Maine coast. However, these warnings are likely to extend farther inland.

New England/Long Island are hardest hit due to the rapid intensification of this storm driving fast-developing heavy snow, rising wind speeds, descending wind chill and elevated ocean. Coastal flooding will become a worry – rapidly – southeast New England tomorrow midday and eastern Mass. tomorrow afternoon.

Farther down the coast winter storm warnings for moderate snows extend south to Georgia where several in. away from the coast are likely (NOAA indicates 6 in. south-central GA). Heavy snow…6+ in. along the Southeast/Mid-Atlantic Coast due to the strengthening trough aloft generating enough cold air in the vertical column of the atmosphere to drive all snow near the coast despite relative warm water.

The storm begins to intensify rapidly this evening dipping to 980 MB due east of Wilmington, NC by 1AM. Rapidly increasing gales on the NC Coast at this time. Wind direction is mostly north so cold air from the north feeds the coastal NC/VA storm making for mostly snow as milder marines influence is cutoff. Sleet can certainly occur. By tomorrow at dawn the storm is due east of Norfolk and heaving for just east of Nantucket.

The incoming chill is the strongest of the current cold wave and crosses fresh snow cover throughout the East. Ambient air temperature including “feels like” temperature due to wind will exceed (be stronger than) model output. Expect 1+ days of below zero wind chill in the Mid-Atlantic once underway early Friday and 2 days of these conditions in the Northeast into the weekend.

Pictured: Climate Impact Company wind speed forecast for the Jan. 4-5 storm.

Pictured: Climate Impact Company snowfall forecast for the Jan. 4-5 storm.