Thursday Thunder: Flag Day brings heavy rain & severe threat

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Source: Twin Cities NWS

Thursday Thunder:

While the lead wave in our change to a wetter weather pattern was weak Wednesday, the next one looks stronger and should produce more widespread rainfall Thursday and Thursday evening.

SPC has laid out a slight risk area that includes much of southern Minnesota.

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Source: NOAA/SPC

Here’s the technical “weather geek” speak on the convective outlook from SPC.

…UPPER MS VALLEY/WRN GREAT LAKES INTO ERN NEB…

TSTMS SHOULD BE ON-GOING ACROSS ERN PORTIONS OF THE DAKOTAS/WRN MN AT 12Z THU AIDED BY STG LOW-LEVEL WAA. DESPITE SOME QUESTION ON THE MAGNITUDE OF BOUNDARY LAYER MOISTURE…AREAS AHEAD OF THE ADVANCING COLD FRONT SHOULD BECOME MODERATELY UNSTABLE BY AFTN WITH MLCAPE VALUES BETWEEN 1000-2000 J/JG…AND POSSIBLY HIGHER. AS FORCING FOR ASCENT OVERSPREADS THE AREA…DEEP-LAYER SHEAR WILL INCREASE TO BETWEEN 45-50 KTS AND SUPPORT SUPERCELL STORMS WITH A THREAT FOR LARGE HAIL AND DAMAGING WINDS. ISOLATED TORNADOES WILL BE POSSIBLE…ESPECIALLY AS STORMS INTERACT WITH THE WARM FRONT DURING THE AFTN/EVENING.

SVR PROBABILITIES MAY NEED TO BE INCREASED IN LATER OUTLOOKS AS THE EVOLUTION OF SURFACE FEATURES AND THE MAGNITUDE OF INSTABILITY ACROSS THIS AREA BECOMES BETTER ESTABLISHED.

Tornado Threat?

There may be enough spin or “directional wind shear” to spawn a few rotating supercells Thursday afternoon. Check out the “helicity” fields below from twisterdata.com.

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Source: www.twisterdata.com

You can see there may be enough shear to produce tornadic supercells from Redwood Falls and Willmar into the Twin Cities metro Thursday afternoon. The best chance of a twister producing storm appears to be between 1pm and 5pm if we get enough sun and heating.

Friday looks dry and hot with a high near 90, but dew points may fall into the more comfotable 50s. Thunder looks to return this weekend.

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Source: Twin Cities NWS

Smoke coverage increases:

You may notice an unusual whitish tint to the sky today in addition to the clouds. The smoke plume from the Colorado “High Park Fire” is spreading east, according to this analysis from NOAA’s Fire Detection Program.

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Source: NOAA/NESDIS

PH

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