Dec 16: Snowstorm Potential Sunday-Monday

Today was a mainly cloudy day across the area as a storm brought several inches of snow to the south of the area, mainly in Virginia. Clouds are expected to continue through tonight with less cloud cover for tomorrow, however the main attention at this time is on a potential storm for Sunday and Monday that will likely bring accumulating snow to at least parts of, if not most of the area.

Sunday – Monday Storm Discussion:

Today’s models were almost the complete opposite of those of last night and this morning. Yesterday, most models were well east of the area, with most of the snow staying offshore. This reached a peak this morning, when almost every model except for the ECMWF model kept snow to the east of the area. By this afternoon, however, the models quickly trended west, with the ECMWF model in the lead, showing what appears to be a blizzard for NYC with mixing issues in Long Island. This solution appears to be the western outlier at this time, and at the same time, the 18z NAM/GFS which kept most of the precipitation offshore also seem to be outliers in how they handle the storm, though no solution is completely ruled out yet as there is still uncertainty.

Despite the unusually large uncertainty for this being in the shorter range, there does seem to be enough confidence for at least some accumulations in the eastern parts of the area, and to stay conservative, I went with a Snow Alert, or a less than 30% chance of 3-7 inches of snow. This alert is still low confidence, however, and may be removed or upgraded tomorrow based on the model trends tomorrow. With the models trending west, the potential of at least some flakes in New York City also seems to be increasing, and I went with likely precipitation in the 5-Day Forecast. The western parts of the area appear to be mainly dry at this time, but should watch the trends in case a scenario like that of the 12z ECMWF verifies.

This is not an easy forecast to make, given the large spread in the models, and it may not be until tomorrow night or even Saturday night that we will know for sure what will happen with this storm. There is still a large spread in potentials, and it is possible that the area receives no snow at all, and if the western solutions verify, as much as a foot of snow, or even more could be possible in parts of the area.

At this time, I am going with an in between solution of the potential of several inches of snow for the eastern parts of the area, the potential of light accumulations in NYC and some light snow further west, however this is relatively low confidence and is subject to change. Stay tuned for a full discussion on this storm tomorrow and more updates on this storm throughout the next few days.

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