textproduct: Twin Cities

KEY MESSAGES

- Very hot & humid today. Heat Index values of 100-110 degrees this afternoon with little cooling relief overnight.

- Low chance of thunderstorms this evening, but, if thunderstorms are able to develop they could become severe with heavy rain.

- Hot & humid weather continues this week, although not nearly as intense as today. Continued low chances for thunderstorms as well.

DISCUSSION

Issued at 459 AM CDT Mon Jun 29 2026

Very hot & humid weather develops today as strong warm advection continues over the Upper Midwest, in response to a deepening & anomalously strong low over the Canadian Prairies. The ridging aloft over the region peaks this afternoon with 700 mb temperatures of 17C on the upper end of climatology for June & July. There will be some stubborn low stratus to clear out this morning across central Minnesota & western Wisconsin as rich moisture gets trapped under the stout capping inversion, but otherwise we should see plenty of sunshine today allowing for temperatures to easily reach the low to mid 90s. The very muggy dew points in the mid to upper 70s being advected in from Iowa will limit any run at 100 degrees today, but this will only make the heat index values worse as we are still expected to have a "feels like" temperatures of 100-110 degrees for much of the area this afternoon & evening.

The very hot & humid conditions will also create an explosively unstable atmosphere with most-unstable CAPE values of 5000-6000 J/kg expected to develop this afternoon. To go along with the extreme instability, seasonably strong wind shear values of 30-40 kts will be present across the region as the wind fields strengthen in response to the deepening low to our north. This is a high-ened environment for severe weather we'll have over the region this afternoon, BUT, the very strong capping of 15+ degrees C at 700 mb *should* limit any storm develop the Dakotas & northern Minnesota.

Things change a bit late this evening, as a surface cold front moves eastwards through the area & our temperatures aloft begin to decrease. Some of the larger-scale global models are more robust at initiating a line of convection along the front late this evening & overnight as our 700 mb temperatures cool to more reasonable levels. Instability values will be slightly lower than this afternoon, but still very unstable, so any storms that would be able to initiate tonight could likely become severe with damaging wind gusts & heavy rainfall. Meanwhile high- resolution models are much more sparse with initiation along the front tonight, potentially picking up on some sort of subsidence response to the intense convection expected off to our north. It'll be a classic conditional summertime thunderstorm forecast: probabilities are low (20-30%) that thunderstorms are able to develop, but, the chance for severe weather & heavy rain is high if they do. be sure to monitor forecast trends through this afternoon & evening.

Tomorrow through the holiday weekend, we begin a stretch of mostly similar days as the ridging aloft becomes entrenched over the region. Hot & humid weather continues, although not nearly as hot as today, with max heat index values of 90 to 100 degrees expected daily. Periodic chances for thunderstorms are also present as a number of weak disturbances traverse northwards around the ridge, and any of these thunderstorms complexes could pose a threat for severe weather & heavy rain. Models are widely scattered on resolving these impulses (as expected) so precip probability forecasts are going to remain very broad brushed, but we do look to have higher chances for thunderstorms & heavy rain during the morning hours Tuesday & Wednesday. These morning thunderstorm chances could also impact our forecast temperatures as any day with morning precip & cloud cover with have significantly cooler temperatures than currently forecast. As for daily temperature trends, there is a noticeable departure between the ECMWF & GFS suite of guidance, with the ECMWF members trending much cooler midweek through the weekend. ECMWF AI/ensemble/deterministic guidance suggests we'll see temperatures more in the mid to upper 80s while the GFS members still depict highs in the 90s most days. Excessive heat conditions with heat indices of 100-105 still look likely again tomorrow afternoon across the metro & western Wisconsin, but the heat threat looks more uncertain beyond that.

AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 1244 PM CDT Mon Jun 29 2026

A mix of low VFR to MVFR cigs to start the TAF. Cigs should gradually increase to around 4 to 5kft by late afternoon. Main concern for this period is the threat of thunderstorms this evening. A line of storms should develop across W MN after 00z and trek eastward through the night. It'll gradually weaken as it pushes east and likely doesn't impact our W WI sites. I have introduced a PROB30 as the best option given uncertainty with convection this evening. Cigs will briefly dip to MVFR with any TSRA. Winds S/SE 10 to 15 knots with gusts 20 to 30 knots through early evening with gusts falling off overnight. Winds turn more southwesterly tonight with SW winds prevailing on Tuesday. Additional round of TSRA/SHRA is possible around daybreak, but there is not enough confidence to include in the TAF. W WI sites will see MVFR cigs possible overnight before scattering after daybreak. VFR on Tuesday.

KMSP...Cigs will remain low VFR/MVFR through mid-afternoon. There is a chance for -SHRA/TSRA after 04z and a PROB30 has been included. Additional -SHRA/TSRA is possible around 12z Tuesday AM, but left out given lower confidence.

/OUTLOOK FOR KMSP/ WED...VFR. Chc -TSRA. Wind SW 10-15G25 kts. THU...VFR. Chc PM -TSRA. S 5-10 kts. FRI...VFR. S 5-10kts.

MPX WATCHES/WARNINGS/ADVISORIES

MN...Heat Advisory until midnight CDT tonight for Chippewa-Douglas- Lac Qui Parle-Pope-Stevens-Swift-Todd-Yellow Medicine. Extreme Heat Warning until midnight CDT tonight for Anoka- Benton-Blue Earth-Brown-Carver-Chisago-Dakota-Faribault- Freeborn-Goodhue-Hennepin-Isanti-Kanabec-Kandiyohi-Le Sueur-Martin-McLeod-Meeker-Mille Lacs-Morrison-Nicollet- Ramsey-Redwood-Renville-Rice-Scott-Sherburne-Sibley- Stearns-Steele-Waseca-Washington-Watonwan-Wright. WI...Heat Advisory until midnight CDT tonight for Rusk. Extreme Heat Warning until midnight CDT tonight for Barron- Chippewa-Dunn-Eau Claire-Pepin-Pierce-Polk-St. Croix.