January 18 2019

We are still dealing with the light snow and icy roads this morning. A Dense Fog Advisory is in place where warmer air is trying to move in over snow and ice covered ground. The is a precursor for the problems with the next event is around the corner. As of now, a Winter Storm Watch is in place for Southern Pennsylvania. There will be impacts farther south, but the worst conditions will be north of Baltimore. However we all get into the rapid freezing Sunday. Timing as well as any remaining snow in place is still up for debate.

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Worst And Best Potential Results

This is very complicated but ti simplify this storm I see two basic outcomes. I am going to show you two models with how this weekend could play out. The NAM 3 Km is most aggressive with cold air and icing. This brings in the arctic air and flash freeze as soon as Sunday morning with more snow. This has done a very good job with the last two systems, so we must consider it sincerely.

The European Model (ECMWF) shows the warm air posing north quickly with minimal snow and ice. Then the flash freeze on Sunday. I honestly am spoilt here, but considering the snow in place and recent impacts.

I have to lean towards the colder solution for two reasons. The NAM has performed well recently and Wirth snow on the ground, cold air is slow to retreat in our local northern zones. But I will have a firmer update later today.

1: Worst case scenario

We start with snow Saturday afternoon. Northern Maryland and Southern PA get moderate accumulations. Metro areas likely to thaw just above freezing.
Saturday night: Moderate Ice Storm north of the Hereford Zone into southern PA. Heavy snow near Harrisburg and north of the PA Turnpike. Central Maryland stays wet.
Sunday: Quick return of freezing air.
Saturday afternoon develops snow and mix. Accumulation with freezing line will be in the normally colder inland west/north zone. Metro areas get some snow at the finish

NAM 3 Km Model Timeline

When It May Start?

Showers beging early Saturday Afternoon