916 FXUS63 KMPX 211804 AFDMPXArea Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 104 PM CDT Sun Sep 21 2025
.KEY MESSAGES...
- Isolated showers and storms this afternoon/evening, a small chance for strong/severe storms mainly in southern MN.
- Lingering shower chances Monday, and possibly Tuesday across the south and east.
- Rest of the week, drying out with above normal temperatures of highs the mid 70s.
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.DISCUSSION... Issued at 100 PM CDT Sun Sep 21 2025
Today... Interesting weather setup with small and compacts upper level low spinning across northwest Minnesota. Upper level ascent ahead of this PV anomaly, was leading to clouds and some rain showers. For the rest of today, expect isolated rain showers mainly along and north of I-94 from this feature.
Farther south, there was an area of clouds and showers across southeast Minnesota, and these were tied to an area of low level Theta_E advection, This will be the focus for showers and some thunderstorms this afternoon through the late evening. Forecast soundings for later today show low LCLs, a veered hodograph, and around 1500 J/kg of uncapped CAPE. The current thinking is the uncapped nature of the environment should lead to several thunderstorms, and the lack of strong deep layer shear means the updrafts will be short-lived and relatively weak.
However, there is a scenario where a couple storms are able to tap into the marginal shear, and remain somewhat isolated. If this were the case, could see a potential for a brief tornado, and perhaps some large hail. SPC has introduced a 2 percent tornado chance for this reason.
Later this evening, storms will become more elevated as we lose the surface heating. This will bring an end to the tornado threat, but some hail is possible for a few hours past sunset. In summary, the severe weather threat is low, which is why there is only a Marginal Risk, but a few of the stronger storms could pose a tornado and/or hail threat.
Monday and Tuesday... The upper level trough bringing the chances for rain will become more positively tilted and shear out, but this will be a slow process. A few areas of positive vorticity will rotate across the Upper Midwest, and could bring lingering small chances for a light rain showers mainly to the south along I-90, and along/east of I-35.
By Wednesday, confidence in dry weather increases. Upper level subsidence is reflected in increasing surface pressure, so expect more sun than clouds, with light winds expected through the weekend. Temperatures will be in the 70s, with dewpoints in the 50s.
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.AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 100 PM CDT Sun Sep 21 2025
Areas of sct to bkn low to mid-level cu cover most sites this afternoon. We have already began to see areas of light SHRA develop near STC over to EAU which have developed a little faster than what forecast guidance anticipated. Thus introduced tempo groups for SHRA at STC, and EAU for the next couple of hours. Showers and iso areas of TSRA are expected to become more widespread across all sites except for STC, and AXN starting later this afternoon mostly after 22/23z timeframe then progressing from west to east. Confidence lacks on direct impacts at each site so continued with prob30 TSRA mentions but tried to shrink the timing window a bit. Once rain passes, fog is expected to develop late tonight into early tomorrow morning with IFR to LIFR visibilities likely across our western most sites. Southwest winds will remain light becoming variable tonight through the rest of the period as the center of a surface low passes overhead Monday.
KMSP...Best timing for precip looks to range between 00z to 04z this evening. A few pockets of thunder are possible thus changed previously mentioned SHRA to TSRA. Cigs will decrease to near MVFR late tonight into tomorrow morning. There is a potential IFR cigs do occur but lacked confidence with duration thus, used sub 1000kft sct cigs for now.
/OUTLOOK FOR KMSP/ TUE-WED...VFR. Wind NE 5-10 kts. THU-FRI...VFR. Wind NW 5-10 kts. &&
.MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None.
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DISCUSSION...JRB AVIATION...Dunleavy
NWS MPX Office Area Forecast Discussion