Here is the video forecast, showing why the Middle Atlantic region will have a warmup going into the weekend, but all of the Great Lakes and Northeast will have a cold period after that.
During warmer-than-average weather in winters past, we have frequently taken a look at the upper stratosphere for any signs of a reversal that would signal a change to colder and stormier weather. We saw this winter that such a setup is not at all required to have a cold, stormy period. There has been a strong vortex near the North Pole at the 10 millibar pressure level all winter; 10 millibars is just one percent of the typical pressure down here where we live.
But now, just as many of us look forward to warmer times, a high stratospheric reversal has occurred over just the last 10 days. You can see the difference on this map:
Studies have shown that, in a statistically significant way, such a reversal precedes a high-latitude blocking pattern that forces the jet stream southward. The signal may not be as important in spring as in winter, but if we do get the blocking and southward shift in the jet stream, it would suggest chillier-than-average conditions for the North Central and Northeast states, and perhaps stormier weather. Farther south, an increase in temperature contrast and storminess could mean more severe thunderstorms. As always, it will be interesting to see how all of this plays out.
It appears likely that many normal activities can go on through the day Monday, as long as the typical cautions for light to moderate snowfalls are observed. Tuesday will be an <strong>entirely different story</strong>. This map shows the GFS- predicted snowfall through 7 P.M. ET Monday:
The second storm we have been talking about will affect the Middle Atlantic region late Sunday and Sunday night. This GFS forecast map is for 7PM ET Sunday and shows precipitation amounts for the 6 hours up to that time.
This was our snow accumulation projection as of mid-morning. A storm that will develop in the Midwest on Sunday is likely to track to the Virginia-Maryland coastal area by Monday morning, then turn east. It will probably bring some to snow places that get mostly rain out out of the first storm.
Just a 1- or 2-degree temperature difference in the lowest 5,000 feet of the atmosphere can make the difference between heavy wet snow and heavy wet rain. Here is a draft of our snowfall map from mid-morning.
Much can still change with regard to the Saturday storm. This draft map from this morning shows how the accumulations may turn out. The AccuWeather.com staff will be watching this closely. I am happy to see many of our newer forecasters making major contributions.
n the Northeast corridor, this winter has not created much happiness among people who like snow. In New York City, this is the first year out of the last nine to have no 2-inch or greater snow event to this point in winter. Ralph Fato (WxNut27) sent out one of his wonderful charts to illustrate the widespread lateness of the first significant snowfall: