Thursday 10 a.m.
The upper-air feature that has been pumping warm, moist air northward through the Eastern states is getting kicked northeastward by a wider trough that is taking shape farther west. The latter feature is sponsoring the southward push of colder air. Near the core of the cold air mass, temperatures dropped as low as the teens in parts of Montana. A few places had their coldest morning since last winter. In eastern North Dakota, Fargo was hit by gale-force, icy wind gusts carrying the first snow of the season.
The main thrust of the cold air will be across the upper Great Lakes and Ontario, but the leading edge of the change to cooler weather has already reached northern Texas. At Amarillo, it was 64 degrees at midnight with the wind out of south. At 8 a.m. CDT, it was 49 with a north wind gusting past 40 mph! The change to chilly will not be as dramatic when it reaches the East Coast, but it will certainly be noticed. Temperatures will be well up in the 70s in Boston tomorrow... and near 80 degrees in Philadelphia and Washington, D.C. On Sunday, temperatures in those cities will be in the 40s and 50s.
This morning's NMM-WRF run shows the band of rain associated with the leading edge of the change to colder weather crossing the Appalachians by midday Saturday. The rain shown on the map is the predicted amount from 8 a.m. until 2 p.m. EDT.
In the six-hour period after this (2 p.m. until 8 p.m. EDT), the rain band almost totally vanishes. I interpret the maps as suggesting I may not actually need the rain jacket that I will carry along anyway to the Penn State - Northwestern game on Saturday. I always carry the jacket in my golf bag so that if it does happen to rain, it looks like I predicted it all along!
A deck of clouds about a half-mile overhead spread westward from the Atlantic to much of the I95 corridor from DC to Boston early this morning. These cloud decks can be a forecaster's nightmare in the spring because ...
The map below the video is one of the GFS solutions for where the southeast storm will be early Saturday. The precipitation is predicted to be farther north than suggested by other models.
It is freezing cold in the Northeast this morning, but this map shows that much more mellow mildness has reached the Plains.
Extensive precipitation straddles both sides of the cold front that was moving through central New York and central Pennsylvania as of mid morning. This radar shows the distribution of rain and snow; some temperatures are added.
The cold front approaching the East shows up quite well in this pressure analysis. Several temperatures are plotted to give you a sense for how much the temperature changes behind the cold front. At Chicago, it went from 60 at 4 a.m. to 39 at 5:19, a 21-degree drop in little more than an hour.
Temperatures on Sunday and Monday will range from the 60s in parts of New England to near 80 in Maryland and Virginia. However, a strong cold front will then trigger and perhaps a few thunderstorms as it ushers in air that will be 30-40 degrees colder than it will be ahead of the cold front.