textproduct: Twin Cities

KEY MESSAGES

- Scattered thunderstorms are expected late this afternoon and evening. There is a level 3 out of 5 risk for severe thunderstorms south of a line from Redwood Falls to the Twin Cities and Eau Claire. Large hail is the main threat, but damaging winds and a couple tornadoes are also possible.

- Additional chances for showers and thunderstorms Wednesday/ Wednesday night and Friday.

DISCUSSION

Issued at 350 AM CDT Mon Apr 13 2026

Stratus is advancing south from northern Minnesota early this morning behind a cold front. The front will stall near a line from Redwood Falls to the southern Twin Cities metro and Eau Claire a bit later this morning. The low clouds will linger through much of the morning, but should attempt to break up by this afternoon. The differential heating along the boundary will increase baroclinicity. An area of low pressure will track along it this afternoon and evening and the SW-NE oriented LLJ will strengthen to 40-45 kts across Iowa. The increased forcing and low level moisture advection will allow thunderstorms to begin developing after 4 PM along and just north of the stationary front. Effective bulk shear in excess of 45 kts should lead to supercells initially with the potential for very large hail (potentially to tennis ball or baseball size), especially if they can remain discrete. Some tornado threat also exists with any storms anchored on the boundary. Convective coverage will increase further into the early evening as capping continues to erode. This will create a messier scenario when storms may congeal into clusters, reducing the large hail and tornado threats for the rest of the evening. The greatest threat for higher end severe should be contained within about 2 to 3 hours after initiation. Little activity is expected south of the front due to an EML with mid level lapse rates exceeding 8.5 C/km keeping the atmosphere capped. It should be noted the CAMs have shifted much farther south over the last 18 hours and now align closer to the AI guidance, which has proven superior over the last several months with consistency and identifying spatial details such as axes of precipitation. However, it remains to be seen precisely where the front will lay out with mesoscale details yet to play out.

the front will resume its trek south behind the system tonight. Tuesday will be dry locally with robust thunderstorm development far to the southeast across Iowa and southern WI. Another shortwave will track northeast from the central Plains Wednesday. The front will return back to the north toward southeastern MN. Showers and thunderstorms will develop Wednesday afternoon and evening, with the greatest coverage from southern/eastern MN into WI.

As that wave departs, another system developing over the northern Plains will push east Thursday and Friday. A warm and more humid airmass will return and a strong cold front will pass through during peak heating Friday. There is good model consistency with temporal and spatial features of this system. Thunderstorms should form on the front mid to late afternoon across eastern MN and WI. Mid level lapse rates around 9 C/km will keep the atmosphere capped until that time, but the strength of the cold front should allow the cap to break. A squall line is likely to form quickly after initiation, posing another severe risk through the early evening. Model consistency drops off beyond that point, primarily due to the handling of the mid level low Friday night and Saturday. ECMWF and CMC are much stronger and farther south with this feature, allowing post-frontal rain and snow to develop within a deformation band. The GFS and AI guidance, on the other hand, are weaker and farther north. This keeps the area dry, aside from maybe some flurries or snow showers on the southern fringes of moist cyclonic flow. Regardless which scenario plays out, colder air returns for next weekend.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1203 PM CDT Mon Apr 13 2026

A somewhat complicated forecast due to potential TSRA from roughly 20-03z across the area combined with some potential IFR/LIFR visibility concerns post-FROPA after the TSRA is out of the area. Winds favor easterly/southeasterly ahead of the incoming TSRA, becoming light and variable after TSRA heads out of the area with speeds remaining 8kts or lower throughout. The confidence to include gusts within the prob30/TEMPO groups with TSRA was too low, however gusts are certainly a possibility with any TSRA that moves through, the magnitude is just uncertain. The key feature to watch will be the position of the warm front as that will directly relate to the best TSRA potential as well as the position of potential IFR CIGS during the period of TSRA. A period of IFR/LIFR is likely after the TSRA ends from roughly 06-15z depending on location due to low level fog/CIGS, which wraps up quickly after 14-15z.

KMSP...Kept the previous TEMPO from 22-01z intact as this period is most likely to see TSRA, with a start time perhaps an hour earlier as far as the first storms to appear. Lingering -SHRA is less certain and could contain brief thunder, however the post TSRA period is less certain with guidance handling it in dramatically different ways. There is solid consensus for a 5-6 hour period of IFR due to fog after 08-09z, ending around 15z.

/OUTLOOK FOR KMSP/ WED...MVFR/SHRA early, then VFR. Wind NE 5kts. THU...VFR, chc MVFR/-SHRA. Wind N 5-10kts. FRI...MVFR/SHRA likely, chance -TSRA. Wind SE to SW 10-15G25kts.

MPX WATCHES/WARNINGS/ADVISORIES

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