monitoring a potential winter storm this weekend

As many of you have probably heard, there is a potential winter storm on the horizon for this weekend. That said, there is considerable uncertainty regarding the track of the storm which will have major implications on the exact forecast of snow vs rain and any potential accumulations. This post will analyze model data and show 2 potential outcomes for this storm system, as well as share what we do and don't know. 

The image above is the 12z run of the GFS model for Sunday at 7am. Previously, this has shown the heaviest snow along and NW of the I-95 corridor. However, there has been a notable trend southward with this latest run, with the heaviest snow south of I-70 and into southern MD. Whether or not this is a trend is unknown as it has only been 1 run of the model.

As far as temperatures go, most of the region is near or below freezing on the GFS, with temps in the 30-33 degree range. While not ideal, its certainly cold enough for snow especially with heavy precipitation rates. This is due to high pressure to our north funneling in colder air, and favorable temperatures at about 5,000 feet which look to be well below freezing on the GFS. 

This image above is the EURO model for 10pm Saturday night. This model has been consistently showing a swath of heavy snow across central and northern MD. Additionally, the EURO has historically been more accurate than the GFS, so I am more keen to lean towards the EURO. 

For temperatures, they are a bit warmer to start, but then cool to at or just below freezing as heavy precipitation results in dynamic cooling. Even with temps hovering near freezing, snow should stick fairly easily as the temperatures at 5,000 feet are also well below freezing.

The final model we will show is the NBM probability map. This image above shows the probability of 4 or more inches based off a blend of models, which is a good way to look at things this far out. The highest probability remains NW of I-95. The probability in those areas is 30-40%, which is fairly high for this far out and bears watching closely. 

Courtesy goes to Tomer Burg for these amazing NBM graphics. 

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Now that we have gone through the model data, lets talk about what we do know vs what we don't know. 

What we know is that there will be a storm near the coast late on Saturday and into Sunday. There is potential for significant accumulating snow, a wintry mix, or all rain depending on the track. What we don't know is what the exact track will be, where the rain snow line will set up, or how much accumulation there will be.

We are still 5 days out, with plenty of time for change, and it is WAY too early to start throwing out model snowfall accumulations or official snowfall forecasts. For now, please stay tuned to the forecast and pay attention to any changes that WILL occur over the coming days. We should have much more confidence as we head into Wednesday afternoon.