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!
Some bands of rain broke out in the I-95 corridor, the most important of which brought a batch of heavy rain to the New York City area between 8:30 and 10 a.m.
in response to the approach of a deepening trough from the Plains, a Midwest low pressure area will grow stronger as it moves east to arrive on the New England coast Saturday morning.
In the I-95 corridor from D.C. to NYC, temperatures will be up past 80 this afternoon. However, between now and Saturday, a major change is on he way.
In eastern New England, an onshore flow of cool damp air prevailed all morning. There could be a last-minute warmup this afternoon. The affected areas will certainly be warmer tomrrow morning than they were this morning.
Now, out-of-season warmth is set to be the rule through midweek from the Ohio Valley to much of New England. Peak leaf color in Pennsylvania and New Jersey ranges from now northern mountains) to Halloween (in parts of South Jersey).
The Pacific storm caused some strong thunderstorms in northwest Oregon yesterday, bringing an end to a very long hiatus in the need for tornado warnings there. Note also the lack of tornadoes in eastern Tennessee.