Weakening thunderstorms Tuesday morning; hot, humid, stormy for July Fourth

Updated flash flooding conditions at 8:15 a.m. on Tuesday

Serious flash flooding is occurring this morning in southwestern Minnesota. There have been isolated rainfalls of 6 to 8 inches reported. Roads are flooded.

The National Weather Service has expanded the area of flash flood warnings to include all or part of ten counties from near Luverne in Rock County northeastward to near Bird Island in Renville County.

Earlier this morning

Thunderstorms blew up overnight from southwestern to northeastern Minnesota in response to the low-level nocturnal jet stream. Very heavy rain caused flooding in southwestern Minnesota, including in Lyon, Murray, Redwood, Renville, Yellow Medicine and Kandiyohi counties. The flood and flash flood warnings shown below are scheduled to expire at various times this morning but will likely be revised based on conditions.

Some of the lighter rain has been crossing the Twin Cities area northeastward.

Radar shows the ongoing precipitation across southern and central Minnesota this morning:

That jet stream typically weakens after sunrise as the heating of the day creates vertical mixing. So I expect that the storms west of the metro area will diminish and end this morning.

Severe storms possible in northwestern Minnesota this morning

Northern Minnesota will continue to experience areas of showers and thunderstorms. A severe thunderstorm watch remains in effect until 9 a.m. for part of the western edge of Minnesota as severe storms race eastward across the Dakotas. Some storms could cause wind damage when they reach Minnesota.

North central and northeastern Minnesota will continue to have periods of showers and thunderstorms from this morning through Wednesday.

Tuesday will be a warm and more humid day with high temperatures from the upper 70s to the upper 8os.

Flooding possible north

Thanks to recent rains and more expected, a flood watch has been issued from this evening through Wednesday for much of central and north central Minnesota including Brainerd, the Iron Range, Ely and International Falls.

Sticky, stormy Independence Day

Our Fourth of July will be hot. High temperatures are likely to range from the low 80s to the low 90. The Twin Cities should reach about 92. And it will be quite steamy with dew points well into the 70s across central and southern Minnesota.

Combine that heat and humidity with the usual urban heat island effect, and the National Weather Service has issued an Excessive Heat Watch for the 7-county metro area for Wednesday.

Thunderstorms are likely to develop again tonight over central and northern Minnesota. Some of those storms could linger into the morning and reach the Twin Cities area around daybreak or a bit later.

More numerous thunderstorms are likely to develop later in the day, mainly during the afternoon and evening in response to heating and support aloft. Locations and timing of storms is quite uncertain as prior convection will have created a rather chaotic atmosphere. As of now, it looks as though thunderstorms, some of them strong and possibly severe, will build southeastward across the state and reach the Twin Cities area in the evening and then track farther southeast toward Rochester.

There is a slight risk of severe thunderstorms, meaning that scattered severe storms are possible, for much of Minnesota and into Wisconsin Wednesday and Wednesday night. Fireworks might be in jeopardy in some locations.

Quieter, cooler, less muggy weather will then come our way for at least Thursday, Friday and Saturday.