Area Forecast Discussion

KEY MESSAGES

- Widespread showers (80 to 100 percent chances) and embedded storms through mid afternoon. Severe weather is not expected.

- Winds behind this first area of rainfall will gust between 40 and 50 mph out of the east.

- Scattered thunderstorms will pose a risk of severe hail and wind gusts along and west of I-39 from mid afternoon through this evening.

- Cooler temps Tuesday through the end of next week. There is a less than 20 percent chance of a freeze Thursday night and a 20-40 percent chance of a freeze Friday night.

SHORT TERM

Issued 140 PM CDT Mon Apr 27 2026

Rest of the This Afternoon and Tonight:

Warm advection band of rain and embedded thunder continues to move to the northeast. On the back edge of this rain, winds are still gusting to between 40 and 50 mph. Latest observations are closer to 40 mph. The back edge of this area of rain should exit to the east/northeast between 2 and 230 PM.

Attention then focuses to the west where some clearing has occurred over Iowa and a cumulus field has developed. A narrow band of scattered storms is starting to develop across portions of central to north central Iowa in an axis of increasing CAPE. Other narrow low level convergence zones exist across eastern Iowa, which should provide focus for additional development. With some daytime heating to the west, surface based CAPE will approach 1500 J/kg, mixed layer a bit lower at 1000 J/kg. This nose of instability will enter southwestern WI during the mid/late afternoon as the aforementioned boundaries and convergent zones approach.

Scattered storms will pose a marginally severe hail threat and a localized downburst wind threat. The tornado threat hinges on maintaining some sort of backed, southeasterly flow. Guidance indicates as the afternoon progresses, low level winds veer more to the southwest, so the overall tornado risk has decreased, but if a cell can latch on to the southeasterly winds, it has a chance for a brief tornado. The area of main concern with this would be Iowa/Lafayette/Green/southwestern Dane counties.

As the surface low moves steadily to the northeast into this evening, the associated surface boundary will be progressive. Scattered storms will move steadily to the east, exiting over Lake Michigan after 10 PM.

Gagan

LONG TERM

Issued 140 PM CDT Mon Apr 27 2026

Tuesday through Monday:

Cooler, drier conditions will build into the region Tuesday, though low clouds will hang on for at least the morning. Northwest flow aloft begins to take hold and will send a few embedded shortwaves our way. Timing these waves will be the trick, but blurring ones eyes there is a chance for showers Wednesday evening into Thursday morning.

Surface high pressure builds in the region for the end of the week and at least the first portion of the weekend. Will need to keep a close eye on frost/freeze potential Thursday and Friday nights. Right now, the better opportunity for a freeze looks to be Friday night.

Northwest flow aloft will remain in control this weekend into early next week. Another shortwave passage is progged for the latter half of the weekend, with the next chance for rain slated for late Sunday into Monday morning.

Overall, this is a cooler and drier pattern for the next week or so. The GEFS CIPS analogs maintain a cooler than average pattern and temperatures will be at or below average for the next week or so. Rainfall chances will be there every 2-3 days, but should be quick hitters in this fast flow.

Gagan

AVIATION

Issued 140 PM CDT CDT Mon Apr 27 2026

The first round of rain and embedded thunder will exit to the northeast by mid week. Behind this area of rain, easterly winds will gust to between 35 and 40kt for a short period. Winds will then reestablish out of the southeast during the mid to late afternoon and then to the southwest as a cold front approaches this evening. MVFR to in some cases IFR ceiling are building in behind this rainfall, though visibility outside of heavy rain downpours will remain VFR.

Scattered storms will move across southern WI through 04z, and winds will shift more to the west as the front moves through. MVFR ceilings will persist into Tuesday morning, gradually lifting and breaking up toward midday Tuesday

Gagan

MARINE

Issued 140 PM CDT Mon Apr 27 2026

Gusty winds on the backside of an area of rain have prompted a gale warning for the southern half of Lake Michigan. Wind gusts to just above gale level are expected until 7 PM. A small craft advisory for the near short will go back into effect at 7 PM through 1 PM Tuesday for gusty winds and waves between 5 and 8 feet.

High pressure will gradually build into the region beginning Tuesday, this will result in gradually decreasing winds and waves. Light winds and waves between 1 to 2 feet are expected much of the rest of this week.

Gagan

MKX WATCHES / WARNINGS / ADVISORIES

WI...None. LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 2 PM Monday.

Gale Warning...LMZ080-LMZ643-LMZ644-LMZ645-LMZ646-LMZ669- LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874- LMZ876-LMZ878 until 7 PM Monday.

Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646...7 PM Monday to 1 PM Tuesday.