112 FXUS63 KMPX 121716 AFDMPXArea Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 1216 PM CDT Fri Sep 12 2025
.KEY MESSAGES...
- Very warm and humid for the next several days. Highs in the upper 80s to lower 90s this weekend.
- Chance of thunderstorms this afternoon and evening with additional chances next week.
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.DISCUSSION... Issued at 324 AM CDT Fri Sep 12 2025
It`s a quiet and mild morning with scattered high clouds streaming east across the region. Some patchy fog and low clouds have developed in Wisconsin, but the most widespread fog remains to the east. Any fog will burn off quickly after dawn. An Omega pattern remains in place across the country with the ridge axis stretching from Texas to Minnesota. A weak disturbance will lift north across the Plains, then turn east and crest the ridge this afternoon and evening across the southern half of Minnesota and Wisconsin. Steep lapse rates greater than 7.5 C/km, pwats in the range of 1.5 to 1.75 inches, MUCAPE of 500-1000 J/kg, a persistent weak LLJ, and a stalled frontal boundary draping northern IA or southern MN will all aid in the potential for thunderstorm development this afternoon and evening. The boundary layer will remain dry, however, and some CIN is expected to remain. Many CAMs show some scattered thunderstorms by early afternoon across western Minnesota, progressing east through the rest of the day and into the early evening. Introduced 30-50% PoPs across the whole area.
The surface front is expected to lift north into southern Minnesota Saturday. A hot airmass to the south characterized by 925 mb temps exceeding +27C will send highs into the low to mid 90s. Cooler air to the north and southeast flow will keep highs elsewhere in the mid 80s. Winds shift more southerly area wide Sunday, and while the intensity of warm air aloft will ease a bit, a larger portion of the region will reach the upper 80s to lower 90s. Combined with dew points around 70, heat indices will likely top off in the mid 90s.
The ridge shifts slightly east Sunday, and by afternoon an upper trough will advance toward the Upper Midwest. It will become a bit negatively tilted Sunday evening and spread a 40-50 kt mid level jet into western Minnesota. Lapse rates will remain weak, but an uncapped atmosphere and stronger forcing arriving should allow storms to develop in the afternoon and evening. SPC highlights western Minnesota in a day 3 marginal risk. PoPs will likely need to be increased in later forecasts.
Sunday`s upper trough will lift north Monday and ridging will build back in its wake. However, additional short wave troughs embedded in the gyre of a parent trough over the northern Rockies will keep the forecast unsettled for much of next week.
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.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 1210 PM CDT Fri Sep 12 2025
Clusters of -TSRA in western/central MN will likely affect most of the TAF sites throughout the first 6-8 hours of the period, present at the beginning at AXN/RWF and pushing eastwards through 00z. Significant wind gusts are not currently expected with -TSRA, with the main impacts stemming from VIS reductions and lightning. Timing wise, AWIPS time of arrival tool on the storms currently in western MN would have them pushing towards STC by 19-20z, MSP/MKT by around 20z, and RNH/EAU by 21-22z. Duration looks to be a few hours at most, on the order of 2-3 for most locations at the current pace. CAMs are performing extremely poor with this entire setup, thus the ongoing -TSRA will be tracked based on movement rather than modeling through the next few hours. After -TSRA move through, winds weaken below 08kts generally from 100-130 as skies SCT200-250 by the end of the period.
KMSP...Model guidance showed little -TSRA which is why the prob30 was removed with the 15z AMD, however given current activity a TEMPO has been introduced from 20-22z based on the movement of what is currently in Renville County. -TSRA may arrive 10-15 minutes prior to 20z if further cu develops ahead of what is present. The window for -TSRA should be fairly tight, with little persisting beyond 22z as it moves over western WI.
/OUTLOOK FOR KMSP/ SUN...VFR, chc MVFR/-TSRA late. Wind SE 5-10kts. MON...VFR, chc MVFR/-TSRA. Wind S 5-10kts. TUE...VFR, chc MVFR/-TSRA pm. Wind S 5-10kts.
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.MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None.
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DISCUSSION...Borghoff AVIATION...TDH
NWS MPX Office Area Forecast Discussion