Let your guard down for one minute and things change in a hurry. What had seemed to be a rather dull week just got a little more interesting. A series of low pressure will travel over the southeastern CONUS and off the East Coast. These lows will bring the chance of rain to the area starting as early as Tuesday morning. As the first low passes to the south, there could be enough moisture north of the low to support wintry precipitation across ENC.

 

GFS model forecast precipitation type Tuesday morning.
GFS model forecast precipitation type Tuesday morning.
NAM forecast model precipitation type on Tuesday morning.
NAM forecast model precipitation type on Tuesday morning.

The past 24 hours for these models have been a trend northwestward with moisture which has led to the change in my forecast thought. The ECMWF was hinting at this possible scenario last week when the GFS wasn’t but ended up backing off to a light rain scenario. It’s uncertain if the trend northwestward will hold up or enough cold air will be in place to support significant precipitation amounts but will all models trending this direction the possibility increases.

Southwesterly flow aloft will bring above freezing temperatures over the area before all the precipitation has moved out leading to snow changing over to sleet/freezing rain (rain along the coast) before ending Tuesday evening.

Light accumulations are possible with areas seeing the highest accumulations near the coast where the bulk of precipitation is forecast to fall. Areas as far inland as Rocky Mount could see accumulations of 0.50″ or greater depending on the track of the low.

As the first low pulls away from the area, there will be a lull in activity as the next low travels across the northern Gulf of Mexico. It is at this point the track of the low is very important as there is a small window of opportunity for wintry precipitation.

GFS forecast model precipitation type for Wednesday night.
GFS forecast model precipitation type for Wednesday night.
NAM forecast model precipitation type for Wednesday night.
NAM forecast model precipitation type for Wednesday night.

As the low strengthens off the FL/GA coast it will moisture to its north will be brought over ENC. At this time there appears to be enough cold air over the inland sections to support all snow initially. The coastal sections would most likely see a mix to mostly rain event with above freezing mid-levels.

SREF plumes from Rocky Mount, NC.
SREF plumes from Rocky Mount, NC.

SREF plumes show the models picking up on light accumulation Tuesday from the first low as well as the higher accumulations from the following low.

Probability of snowfall greater than 1" over a 24 hour time frame Wednesday night through Thursday night.
Probability of snowfall greater than 1″ over a 24 hour time frame Wednesday night through Thursday night.
24 hour probability of snow accumulation greater than 4" Wednesday night through Thursday night.
24 hour probability of snow accumulation greater than 4″ Wednesday night through Thursday night.

My updated forecast for Wednesday night’s winter storm:

Winter-Storm-Threats

Winter-Storm-Threats

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