Thursday, 11:40 a.m.
There's a growing area of the country that is just plain dry. Much of that covers the Deep South and the Southeast into the mid-Atlantic states, but there are portions of the Rockies that could use some moisture. Thankfully some of these areas got some rain in the past 24 hours, namely the eastern Rockies and western Plains, and there will be more where that came from.
Look at the latest projected precipitation across the country from this morning through Sunday evening:
A series of upper-level disturbances will come through California and across the Rockies, then out into the Plains and Midwest. The air ahead of these disturbances will become increasingly warm and moist, while it turns cooler, naturally, behind them. So, as each one moves along in the flow, it will be able to tap into this increasing contrast of air masses, and that will lead to episodes of rain and thunderstorms. And some of those thunderstorms will be severe, plain and simple.
As far as the severe weather risk is concerned, let's break it down. This afternoon and into tonight, the main area will be over the western Plains as the first of these disturbances comes on through:
These thunderstorms will weaken tomorrow as they head into the Midwest, and things will become relatively quiet later tomorrow into tomorrow night. However, more disturbances will follow over the weekend, and thunderstorms will erupt anew on Saturday. Some will be across the middle and upper Mississippi Valley into the Ohio Valley and lower Great Lakes, with a concern for severe weather in these areas, but the worry for severe weather may be greater later in the day and at night back across Kansas, Oklahoma and parts of Texas.
As another feature streaks out of the southern Rockies and out onto the Plains Sunday, it will push the dry line out to the east across the southern Plains, with strong to severe thunderstorms almost sure to erupt along and ahead of it. At the same time, some of that moisture will get wrapped back around the developing surface storm in the central Plains, resulting in a growing area of rain and elevated thunderstorms north and northwest of the storm. In some cases, it will even change to snow!
This is all well and good for the eastern Rockies and Plains into the Midwest int terms of moisture in the coming days, but if you go back to that first image, where's the love for the South? The Southeast? the central Appalachians and the mid-Atlantic? Most of these areas will get virtually no rain through Sunday, and probably a good bit of Monday before a cold front finally starts to move into the Great Lakes, the Ohio, and the Tennessee Valleys late Monday or Monday night. And by the time this front moves over the Appalachians and heads into the East Tuesday night and Wednesday, there will be far less moisture left behind. The only way these latter areas can truly cash in on any moisture is if there is still another wave of low pressure traveling along the front that can bring it to a halt for a time and lead to a period of enhanced rain or convection. But that's a long shot right now.
Instead, it just gets warmer into and through the weekend. MUCH warmer, in fact. Look at the projected 850 mb temperatures for late Sunday from the Canadian model:
That +10C area runs along the north shore of Lake Ontario to Portsmouth, N.H. In a well-mixed environment with some sunshine, that would equate to surface temperatures as high as the upper 70s near sea level! That's probably not the case in these northern areas, but not far to the south it will get that warm, and probably warmer, as the 850 mb temperatures of +15C or better in Maryland and Virginia could mean highs in the middle 80s or better! 90 in Washington, D.C.? It could happen! It was just 10 years ago that parts of southern New England saw it reach 90 in mid-April, and many will remember the April heat wave in the bicentennial year of 1976. Even if it isn't that warm, it will be much above normal and with no rain, it will further dry out an already very dry landscape. That will only serve to increase the already very high fire danger throughout the East.
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.