An active weather pattern is setting up for the Mid-Atlantic region which will feature an energetic Arctic frontal passage later tomorrow and then a weekend storm threat. It is quite certain that the frontal passage later tomorrow and early tomorrow night will generate the first snowflakes of the season for much of the I-95 corridor, but the weekend system is far from being clear as to its impact on the region and requires more time for clarification.
An Arctic front with copious upper-level support will push towards the I-95 corridor later tomorrow and snow showers are likely to break out. Given the strength of the upper-level energy, there is a chance that a burst of heavier snow (aka snow squall) takes place late tomorrow or early tomorrow night which could cause a minor accumulation of snow in a hurry. Winds could also become a factor early tomorrow night with gusts possible up to 50 mph. Once this front slides through the region, there will be a reinforcing shot of Arctic air and temperatures on Wednesday will have a hard time reaching the 30 degree mark for highs.
A strong wave of energy will approach the west coast of the US on Wednesday (circled area on forecast map above) and then trek across the country reaching the southern states by Friday afternoon. There are simply too many details to be ironed out for this particular system to have a clear handle on the potential weekend scenario. Odds favor rain at this point in the immediate I-95 corridor, but a shift to the south and east of the main upper-level wave could change those odds somewhat and lean more towards snow. In fact, the change in the Euro model forecast from last night-to-this morning has been somewhat subtle, but rather significant if it is part of a developing trend. The upper level wave (circled areas below) for the potential weekend system is a little stronger and a tad farther south on the latest 12Z version of this particular computer forecast model (right) compared to last night's 00Z version (left) for the same Friday afternoon verification time of 18Z. Stay tuned on this as we will likely not have a good handle on it until at least the mid-week time period when the upper wave moves from the eastern Pacific Ocean to over California. It is quite certain that more very cold Arctic air will follow the weekend system into the central and eastern US.
Meteorologist Paul Dorian