textproduct: Twin Cities

KEY MESSAGES

- Long duration heat wave begins Sunday & persists through next week. Monday will be the hottest day.

- Periodic chances for thunderstorms Sunday through next week. A few thunderstorm complexes capable of severe weather & heavy rain are possible.

DISCUSSION

Issued at 329 AM CDT Fri Jun 26 2026

ANother quiet & seasonally cool day today, but we'll see a major pattern change to summer develop this weekend & really peak through next week. We'll already see the start of warm advection & increasing dew points through the day today, although temperatures will likely top out in the upper 70s most places. Isolated rain showers & possible late this afternoon & into this evening as the forcing from the low-level jet ramps up. The greatest coverage of these showers looks to be across central Minnesota & western Wisconsin. The warm advection continues to increase into Saturday with our first-above normal day in two weeks expected as highs warm into the mid 80s & dew points continue to increase into the 60s. Thunderstorms are likely to develop Saturday afternoon across the Dakotas as the first of a series of impulses rides along the strengthening ridging aloft over the Upper Midwest. These storms Saturday night should follow the upper level forcing & remain off to our north & west through the night.

Sunday is when the heat and humidity really begin to take hold as the ridging aloft continues to amplify over the Upper Midwest. Highs are expected to reach the 90s across much of Minnesota and Wisconsin, with dew points rising into the upper 60s and 70s. That combination will make it feel closer to 100 degrees in many locations by Sunday afternoon. Any morning storms or clouds could slow the temperature rise in some areas, but the overall trend is toward a very warm and humid day. Temperatures will also be warming aloft, with 700 mb temperatures forecast to reach 15 C over the area. This very strong capping should prevent any thunderstorms from developing over much of our area, but we'll have to monitor the gradient of how much these temperatures cool off to the north across central Minnesota & northwest WI. The current model consensus generally keeps any thunderstorms Sunday evening off to our north across northern Minnesota, but there is still enough uncertainty to continue to mention a threat for severe thunderstorms & heavy rain across central MN/western WI Sunday night.

Monday continues to look like the most concerning day of the forecast period. Temperatures are expected to climb well into the 90s, if not approach 100, with tropical dew points well into the 70s expected. Just how hot we get & how high heat indices can reach will depend greatly on any remnant precipitation or cloud cover from the possible storms Sunday night. If we remain clear & daytime heating is maximized, widespread dangerous heat index values of 105 to 110 are likely with little cooling relief expected overnight or over the next few days. This level of heat can become dangerous quickly, especially for anyone without reliable air conditioning, those working outdoors, young children, older adults, and people with chronic health conditions.

In addition to the heat, Monday brings a conditional but potentially significant severe thunderstorm threat. CAPE values will easily rise above 5000 J/kg given the extreme heat & humidity, while seasonably strong shear values will also be present from a developing jetstreak to our west. However, the cap will be very strong, likely even stronger than Sunday's, which may prevent any thunderstorm development at all. We'll likely have to monitor any residual outflow boundaries from the previous night's thunderstorms because even the slightest source of lift may be enough to set off intense thunderstorms late Monday afternoon & evening. If any thunderstorms are able to form, they will likely have the potential; for significant severe weather along with torrential rainfall. AI thunderstorm outlook guidance mainly highlights the greatest severe threat across northern Minnesota where the cap is weaker, but still show rather high severe probabilities across our area given the high-end environment in place.

We know it will continue to be hot & humid Tuesday through the rest of the week, but the details become less clear given the chances for daily rounds of thunderstorms & precipitation/cloud cover potentially limiting how warm temperatures can reach during the afternoon. While temperatures are expected to peak on Monday, excessive heat looks likely to continue through most of the week with highs in the 90s & muggy dew points creating severe days in a row of heat index values at or above 100 degrees. The long duration of this heat & lack of any significance cool relief at night will exacerbate the threat to health, especially among at-risk & vulnerable groups.

The main takeaway is that we are heading into a higher impact summer pattern. The heat beginning Sunday and especially Monday will be dangerous, and the severe thunderstorm threat Sunday night into Monday could become significant if storms are able to develop. Now is the time to plan for several days of heat, check on people who are more vulnerable, and stay updated on the latest forecast as thunderstorm details become clearer.

AVIATION /06Z TAFS THROUGH 12Z SATURDAY/

Issued at 1227 AM CDT Fri Jun 26 2026

VFR conditions expected through the period. Skies currently SKC to FEW at 25 kft will continue over the next few hours. Clouds will increase from west to east through the early morning hours will all terminals at BKN-OVC at 20-25 kft by sunrise. By late morning and afternoon, FEW-SCT CU development will occur at 5-8 kft with higher SCT-BKN CIGs at 20 kft. Winds light and VRB or out of the NE through the morning hours, becoming E/SE at 5-10 knots during the late morning and afternoon hours.

KMSP...No additional concerns.

/OUTLOOK FOR KMSP/ SAT...VFR. Wind SE at 10-15 kts, gusts to 20-25 kts. SUN...MVFR CIGs likely AM. CHC of AM TSRA. Wind 10-17G30 kts. MON...VFR. Wind S at 15-20 kts, gusts to 30 kts.

MPX WATCHES/WARNINGS/ADVISORIES

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