Monday, 11:25 A.M.
Sunday was one of the stormiest fall days I can ever remember. In fact, it was one of the worst severe weather outbreaks I've seen at any time of the year, much less in November! Here are the reports from yesterday:
The 81 tornado reports may well be cut in half to the actually number of tornadoes, but that's somewhat immaterial at this point, given the number of fatalities, the devastation, and the large number of power outages.
What caused such a massive outbreak of severe weather in the first place? Several factors, actually. For one, we had record heat in parts of Texas and Arkansas for starters, and the air was being pull from there into the circulation of a deepening storm heading across the Midwest into the Great Lakes. Two, the low-level winds pulled high dew point air way to the north, with 60-degree dew points all the way Chicago. Three, a vigorous upper-level disturbance was streaking across the Plains, helping to not only lift the warm, moist, unstable air, but also set up some strong wind shear - a change in the wind direction and speed with height. And four, the air mass back over the northern Plains behind pulled into the deepening storms' circulation was quite chilly. Add it all up, and yet get a rapidly deepening storm tapping warm, moist air and triggering severe thunderstorms.
The storm itself raced across the Lakes, and is now along the southeast shore of James Bay. The very strong jet stream winds blowing across the Midwest, the Lakes, and the Ohio Valley have rapidly ushered the cold front off the New England and mid-Atlantic coast, even faster than the models had been indicating late last week! The last of the showers will exit Maine this afternoon, while the front brings showers and thunderstorms across the central and eastern Gulf Coast into Florida.
The air mass is not cold immediately behind the front, so with sunshine and a good downsloping wind east of the Appalachians, the atmosphere will be well mixed, allowing the air to warm up as much as possible. The chillier air will move in tonight and tomorrow, pushing temperatures back below normal in the East for a couple of days, while areas from the Ohio Valley back to the Midwest will be chilly today and tomorrow.
The weather won't be quiet for long. In fact, clouds are already streaming into the Northwest ahead of a much weaker storm off the coast. Rain will spread in to western Oregon and much of Washington this afternoon. The rain will spread into northern California tonight, with showers persisting there through tomorrow into tomorrow night.
By Wednesday night, low pressure will be reorganizing over the western Plains, pulling much colder air southward through the Northwest and northern Rockies. This will mean snow crossing Montana late tomorrow night and Wednesday, spreading into Wyoming later Wednesday, and into Colorado late tomorrow night into Thursday.
Out ahead of the developing storm, southerly winds will transport warm, moist air northward yet again, and it may trigger a much, much smaller outbreak of severe weather from parts of southeastern Kansas and Oklahoma into Missouri and perhaps southern Illinois.
This storm may ultimately wind up as two separate features, with one bringing the front to the East Coast Friday night and Saturday morning, and the second one allowing a wave of low pressure to form along the front. This latter option is to some degree supported by most models. The details of how that shakes out in the wash is still not certain, but it does raise the concern for snow with the storm, specifically in parts of the Lakes, upstate New York and northern New England, if not a little farther south.
After that, a blast of cold air will sweep across the country, bringing us ever closer to winter.
Despite the current chill, warmth is becoming more certain this weekend and beyond from the Plains to the Northeast, even as Erika threatens Florida Sunday night and Monday.
While Danny has been declared an open wave, the low pressure area trailing it will likely have at least a passing impact on the weather along the East Coast next week.
It may be hot now in the Northeast, but much cooler air is drilling into the Rockies and is heading eastward. An even cooler air mass this weekend and early next week will be followed by a stronger warming trend.
The retreat of the jet stream will lead to more warmth than not in much of the country heading into the second half of August.
More concentrated areas of active weather will be the rule into the early part of next week across the country as weak storms move steadily eastward.
A building upper-level ridge over the southern Plains will escalate the heat, while diverting disturbances with showers and thunderstorms around it through the northern Plains into the Great Lakes.