Tuesday 9 a.m.
Here is this morning's video:
This map includes more than 200,000 lightning strokes in the 23-hour period that ended at 6 a.m. today. Note that one area free of thunderstorms covered most of Minnesota and parts of the Dakotas. That area was experiencing the arrival of a fresh cool air mass from the middle of Canada. We expect the drier air to make it all the way to the East Coast tomorrow night.
However, whether the dry air maintains control for a couple of days or is instead routed quickly remains to be seen. The European forecast model says moisture returns quickly, but the main U.S. model does not. Here are forecast maps from both models for this Friday afternoon:
The European model (ECMWF) has damp weather firmly planted from Philadelphia to Boston.
The GFS model shows the moisture well south and and east of where it is depicted on the other map. We do not know which idea is better right now, but other changes on the weather maps, upper air charts, satellite and radar images will give us hints about the likely outcome between now and Thursday.
A number of you have submitted weather photos and graphics that we really enjoy. One person with a keen eye for how to visualize weather and climate events is Ralph Fato of Connecticut, who graciously allowed me to use this graphic about snowfall.
Snowfall amounts yesterday were low from Philadelphia to New York City. Accumulations increased toward the north and northeast.
This map shows the NAM's projection for this Friday night. The isobaric pattern suggests there is a southwesterly flow of mild air from the Gulf states to the Middle Atlantic region. Farther north, we see evidence of the frontal boundary that separates the mild air from chillier air.
A new area of snow now over southern Minnesota should expand southeastward to reach Chicago this afternoon, streak to Pittsburgh this evening, then reach the Philadelphia/New York City area late tonight or early tomorrow morning. This map shows a low pressure area over Missouri.
This map shows expected accumulations.
Check AccuWeather.com's latest info as the forecast ideas mature. This is a draft of the Thursday morning snow accumulation idea.