Wednesday, 11:30 a.m.
It's a fairly busy weather pattern these days, but with a general lack of heat in the pattern, there's not a lot of severe weather. It isn't totally absent, mind you, but there's just not a lot of it. Look at some of the severe weather reports from Tuesday and Tuesday night:
This afternoon and tonight, there will likely be very little severe weather. The Storm Prediction Center has outlined only a small area at risk for severe weather, basically parts of Kansas and Nebraska:
We often see a steady decline in severe weather as we move into the second half of summer. With the sun angles decreasing, we tend not to get as much out of a given air mass as we normally would. And the temperature contrast between north and south is generally not very large, so the types of things that lend themselves to strong to severe thunderstorms are not as present as they are earlier in the season. When you couple that with a relatively cool air mass in place from the northern and central Plains to the Ohio Valley, it's not a pattern conducive to severe weather.
That said, there is still some risk of flooding in various parts of the country. One of those flood risks is in the mid-Atlantic into New England late tonight into tomorrow night as an upper-level trough of low pressure pulls more humid air into the region, then squeezes it out in the form of heavy rain and thunderstorms. To give you an idea of the rain potential, here's the total precipitation forecast through 12z Friday morning:
Note that the axis of heavy rain extends down through North Carolina. It's possible some places may well exceed 2 inches of rain during this time period, and it will likely fall on saturated ground. In addition, the heaviest rains are likely to fall in a relatively short time period, roughly six hours or less. The combination of those two factors can lead to some of the flooding downpours we are concerned about.
That's not the only area at risk for flooding over the next couple of days. As another upper-level disturbance rolls out across the Plains and the Mississippi Valley Friday and Friday night into Saturday, it will generate more rain and heavy thunderstorms, starting over eastern Nebraska and ending up in the Ohio Valley. The NAM projected precipitation totals for 72 hours starting this morning and running through 12z Saturday:
With more typical summertime heat and humidity in place across the southern Plains the rest of the week into the start of the weekend, the region from Nebraska to Indiana will be closer to the heat and humidity, while at the same time a renewed push of cooler air moving in behind a cold front into the northern Plains and Upper Midwest should sharpen the contrast between air masses and help contribute to the heavy rain and strong thunderstorms.
Warmth will expand from the Gulf Coast into the Ohio Valley and mid-Atlantic states by Memorial Day, but the wet and stormy weather will persist in the Plains, and expand across the Mississippi Valley.
Chilly, wet weather will morph into a warm, humid pattern later this weekend into next week, one that will remain unsettled, especially in the Plains and Mississippi Valley.
Severe thunderstorms will erupt over West Texas late tonight and tonight, but they'll become more widespread over a larger percentage of the Plains states later tomorrow and Saturday.
After a brief cool spell, much of the country from the Plains on east will turn warmer Friday through Sunday, but there will also be more clouds, showers and thunderstorms around as well.