Tuesday 7:15 a.m.
My video shows the heat wave setup for the northeastern third of the country and explains why the heat wave should be cut down during the coming weekend.
The map showing today's upper air flow pattern includes a huge high pressure area aloft centered over Ohio. This kind of high is a classic signature for a heat wave. Note how the prevailing westerlies are pushed well north into Canada.
Most of the time when a big ridge is in charge, there is little or no precipitation. Air sinks in high pressure areas, and sinking air becomes warmer and drier. Yesterday, thunderstorms were most numerous in the Southeast and back into Texas, well south of the high pressure center. However, the hot air mass is so humid that some thunderstorms popped in response to intense ground-level heating right into the central part of this high pressure area.
This forecast map of the upper air flow for Saturday shows a big high is gone and the westerlies are expanding southward through the Great Lakes region. This strongly suggests a cold front will be moving into the Northeast with thunderstorms (perhaps severe) followed by an end to this heat wave.
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.