Flash flood and severe risk through Thursday; early freeze this year?

A stalled front straddles the Iowa-Minnesota border. It’s basically the dividing line between summer and fall across the Upper Midwest. Sticky red summer air lingers south of the front. The first chilly blue puffs of fall gather to the north.

Wednesday afternoon temperatures, via Oklahoma Mesonet

A series of low-pressure waves rides the front in the next 36 hours. Expect several waves of rain and thunderstorms through Thursday.

Let’s break down the potential for flooding and severe storms.

  • Flash flood risk: There is a flash flood watch for southern Minnesota south of the Twin Cities overnight and Thursday. Widespread 2- to 4-inch rainfall totals are possible across southern Minnesota. Locally higher totals are possible.

The risk for excessive rainfall totals of several inches favors southern Minnesota.

  • Severe weather risk: Thursday there is an “enhanced” for severe storms producing damaging winds and hail Thursday. Tornadoes are possible. The primary risk is afternoon and evening. This includes the Twin Cities area.

Bottom Line: Expect waves of rain and thunder through Thursday. Locally heavy rainfall is possible. Severe storms with damaging winds and hail are likely Thursday. Tornadoes are possible in the risk zone. As we like to say in the weather biz, maintain ‘situational awareness’ through Thursday.

Nicer weekend

The weekend looks milder and mainly dry. Good timing. Even cooler air arrives next week.

National Oceanic and Atmospheric Administration, via Weather Bell

Instant fall of 2018?

Last weekend’s summer heat burst marked the 18th and 19th days at or above 90 in the Twin Cities this year. September is running 6.7 degrees warmer than average so far.

But the upper-air pattern buckles into a much colder hemispheric flow pattern late next week.

NOAA

Our first shot of real fall air arrives least next week. Highs in the 50s in northern Minnesota and low 60s south will feel brisk. Temperatures will run 10 to 20 degrees cooler than average for a change.

Frost is likely up north, and the Twin Cities may flirt with the 32-degree mark by late next week. Frost is common this time of year in northern Minnesota. The average date for the first 32-degree temperature in the Twin Cities is Oct. 10.

Stay tuned.