textproduct: Twin Cities

KEY MESSAGES

- Multiple clusters of storms are expected across southern MN tonight to the north of a warm front. There is a level 2 of 5 risk of severe weather, with damaging winds being the highest risk.

- A low confidence precipitation forecast through Labor Day weekend, with multiple low chances for rain.

- Summer-like temperatures and humidity continue through Labor Day weekend.

UPDATE

Issued at 836 PM CDT Tue Sep 1 2026

Regional radar and satellite imagery shows the incoming cluster of showers and storms focused primarily over the monster supercell thunderstorm ongoing over the southeast South Dakota/northeast Nebraska border. The trajectory of this individual storm looks to take it eastwards into Iowa and should remain south of our area for now, however we will keep a close eye on some further development out ahead of it over north- central Iowa that is moving northeast towards our southernmost counties along I-90. The expectation as the night continues to progress is for this cluster of showers and storms to focus along the leading edge of a developing low level jet, which you can see via the SPC mesoanalysis page within the MLCAPE gradient focused over southern Minnesota, and this gradient is where we expect any potential stronger storms or MCS/bowing line segment to favor moving across. This would place the area from roughly Redwood Falls through Mankato and southwards within the most likely area to see a stronger thunderstorm with the potential for severe level wind gusts, especially if it takes on the classic bowing shape indicative of stronger winds. The CAM guidance has been waffling on the pacing of the storms since the afternoon, with each run either speeding or slowing the pace of the line segment as it moves through. At slowest, it is still moving eastwards at around 40-50mph, so some severe level winds up to 60mph are possible despite lower level inversion building underneath the low level jet, with even higher gusts possible mainly within any potential bowing segment. The more recent HRRR runs have favored the bowing shape to occur as it passes through Mankato and approach Rochester in southeastern MN, which mimics the location of the MLCAPE gradient as of 0130z. With the Twin Cities at least 2 tiers of counties north of the gradient, it is looking less favorable to see the stronger portion of the storms, however there is still at least some activity expected north of gradient in the form of some scattered rain showers. These showers look to persist into the mid morning tomorrow before dissipating, and could contain some intermittent lightning but are not expected to be strong whatsoever. For now, we keep a watchful eye on the radar and satellite as we await whatever storms reach us later tonight and into the morning.

DISCUSSION

Issued at 112 PM CDT Tue Sep 1 2026

Water vapor imagery this afternoon shows a subtropical ridge centered over the bootheel of MO, with a monsoon shortwave coming out of Wyoming that will run around the north side of the ridge through the night. At the surface, there's a stationary front a little north of the I-80 corridor in Iowa, with dewpoints pooling up into the upper 70s along it. As we go through the night, the WY shortwave and IA warm front will work together to support an overrunning convective event over southern MN. Current expectations are that storms will develop this afternoon in the Dakotas associated with the shortwave, with elevated storms developing north of the warm front near the MN/IA border shortly after sunset as the LLJ over IA starts to ramp up (eventually getting up into the 35-40 kt range). We're seeing the idea from the HRRR and other CAMS that we could see multiple clusters of storms develop on the nose of the LLJ, with the convection in the Dakotas that develops this afternoon eventually sweeping up any clusters ahead of it late tonight. The favored zone for heavy rain and severe potential will be on the nose of the LLJ and along the MUCAPE gradient. The HREF/REFS continue to show these two features lining up along the MN/IA, with the southern two or three tiers of counties in MN being most at risk for storms, heavy rain, and severe weather tonight, which matches up well with the Day 1 Slight Risk from the SPC. From the severe weather perspective, instability (muCAPE > 3000 j/kg) and deep shear (over 40 kts) are certainly favorable for severe weather, but weak mid- level lapse rates and overnight timing/nocturnal stabilization will be limiting factors that will put a ceiling on this being a significant severe weather setup.

For the rest of Wednesday, we're expected to be dry as the atmosphere recovers from the early morning convection. We'll have height rises through the day, with easterly low level winds, so we may have to battle some morning stratus as the low level moisture gets trapped beneath a building inversion. Those easterly winds and potential for morning clouds will result in Wednesday being the "coolest" day of the work week, with highs generally in the low to mid 80s, with ever increasing dewpoints, as tropical dewpoints in the 70s begin spreading back north across southern and southwest MN.

Going into Wednesday night, we'll begin to see the stationary/warm front lifting back north across the area. The LLJ will not be as strong as what we see Tuesday night, but WAA will still be present. HREF shows over 2000 j/kg of muCAPE coming up with that warm front and the presence of the weak WAA will give us a chance of storms, but it's highly uncertain if we'll get storms to fire with our subsidence and building cap. This uncertainty is why we ended up with pretty broad 20-40 PoPs across the area Wednesday night as we await some hopefully better clarity on where mesoscale features will be.

Answering the question of where mesoscale features will be will continue to be a headache as we go through Labor Day weekend. We'll see a ridge axis centered over us by Saturday, that shifts to our west Sunday into early next week. That ridge will come with strong capping, along with a rather uncomfortable airmass, as we see highs near 90 Friday and Saturday, with dewpoints in the low to mid 70s sending heat index values both days up into the mid to upper 90s, welcome to Augtember! That ridging will also result in capping. However, given how unstable the atmosphere is, it's not taking much for convective parameterization schemes in the deterministic models to start firing off convection. There is lots of spread with QPF in the ensembles, so the on/off, mostly low chances for PoPs makes sense. Again, where any weak shortwaves happen to meetup with a surface boundary, chaos could ensue, but where that may happen is still uncertain given the capping and weak forcing.

For Sunday into early next week, the ridge axis shifts to our west, with MN/WI transitioning into northwest flow. This is why you'll notice temperatures in the forecast taking a step back after Saturday. We'll still be placed within the northern stream and susceptible to mesoscale shenanigans though. At the moment, it looks like Sunday night through Monday night would be a period with increased storm potential, but there's still time for this to change in the coming days.

AVIATION /00Z TAFS THROUGH 06Z THURSDAY/

Issued at 623 PM CDT Tue Sep 1 2026

The primary factor within the TAF period is the potential for -SHRA/TSRA moving in after 02z from west to east with a cluster of storms over southeastern South Dakota the feature to watch. CAM guidance shows this cluster moving towards southern MN by 02-03z and continuing eastwards before becoming linear and moving across southeastern Minnesota and western WI. The most likely sites to see -TSRA or TSRA are RWF/MKT/EAU, with MSP/RNH having a lower but non-zero chance, and STC/AXN being too far north to get hit with the main band of -TSRA and instead relying on some weaker -SHRA with embedded TS. Winds will become light outside of -TSRA and variable in direction, eventually favoring 120-150 at 5kts. By the 06z issuance, storms should be ongoing and we can pinpoint the timing which for now is based off the most recent runs of the HRRR which have generally captured the storms in South Dakota better than other guidance. Outside of TSRA, VFR is expected. As the TSRA moves through, strong gusts in excess of 40kts are possible mainly for RWF/MKT/EAU alongside a drop to IFR/MVFR as they pass.

KMSP...Kept the prob30 for -TSRA but added some prevailing -SHRA as CAM guidance shows lingering -SHRA after the -TSRA passes. MSP is still on the very northern edge of the potential track of the stronger line of storms, with the line more likely moving along the southern MN border/I-90.

/OUTLOOK FOR KMSP/ THU...VFR, early MVFR/-SHRA possible. Wind SE 5-10 kts. FRI...VFR. Sl chc -TSRA. Wind S 5-10 kts. SAT...VFR. Wind SE 5-10 kts.

MPX WATCHES/WARNINGS/ADVISORIES

MN...None. WI...None.