Thursday, 11:55 a.m.
I'm going to take somewhat of an unusual tack in today's post. Rather than talk about specific storms and fronts, I'm going to look at things in terms of circulation centers. Follow me for a bit, and I think you'll catch on. There are essentially three main storms controlling the pattern right now, but there are little 'whirls,' as I'll call them, rotating somewhat independent of these larger storms, and each one can have plenty of weather associated with them.
Let me start with the colorized water vapor imagery:
And then let's combine that with the 12z 500mb chart:
Perhaps the anchor point to the whole thing is the strong upper-level low over Quebec, a feature that is forcing a much smaller feature - one of those little whirls - to turn southeastward and dive under it as it moves away from the eastern Great Lakes and crosses Pennsylvania. While there i some thunder, most of it is a gentle rain at this point, and much of it will slide off the mid-Atlantic coast early tonight. There will be some stronger thunderstorms farther south, where the sun is shining and it remains hot and humid.
The next upper-level low has been spinning around the Northwest and, of late, the northern Rockies. It has had some severe weather with it over the past couple of days, and there will still be some strong to severe thunderstorms out on the Plains over into the Mississippi Valley this afternoon into tonight. That upper-level low will be near or just north of North Dakota tomorrow morning:
Another one of these little 'whirls' will scoot through the Midwest and into the Great Lakes late tonight and tomorrow, bringing clouds, rain and some thunderstorms through these areas, as well as into the Ohio Valley late tomorrow and tomorrow night. From there this feature will again slide east-southeastward through the mid-Atlantic Saturday before slipping off the coast Saturday night. All of that as the parent upper-level low hardly moves through the weekend by North Dakota and northern Minnesota!
Lastly, there is a much larger upper-level low over the Northeast Pacific. Another one of these little whirls will be aimed at Vancouver Island late this afternoon and tonight, bringing rain into British Columbia, and a few showers to western Washington. The front that is tied to this will mean a little cooling for the Northwest tomorrow into Saturday before heights rise and it becomes much warmer Sunday and Monday.
Two systems will delay the onset of warm weather in the Ohio Valley and the East over the next week or so, but then it should get warm all across the country heading into the Memorial Day weekend.
A turn to much colder air over the Northeast and mid-Atlantic states will set the stage for a rain and snow storm later this weekend before it turns much warmer later next week.
It's warm now, but will turn much colder this weekend, with a storm threat later Saturday into Sunday. Warmth will return by the second half of next week.
Though it is cold now east of the Mississippi, with a couple of opportunities for snow into the weekend, a blast of warmth is due for much of the country east of the Rockies next week.
Warm air will once again surge eastward from the Plains to the East Coast this weekend and early next week. A strong storm next Tuesday and Wednesday will then be followed by colder air later next week.
A storm in Southeast Texas will generate severe thunderstorms this afternoon and tonight, and some wet snow on its western flank as it heads into the Ohio Valley tomorrow.