Area Forecast Discussion

KEY MESSAGES

- Temps rise well above normal Tuesday through Thursday.

- Next chances (50-80%) for showers and thunderstorms Thursday night.

UPDATE

Issued 758 AM CDT Mon Apr 20 2026

Thin high clouds overhead will not prevent plenty of sunshine today. Breezy southwest winds up to 20 mph are expected this afternoon. Low relative humidity values dropping to 20 to 30 percent with lowest values well inland will help dry us out a bit. After a cold start with frost, temperatures are heading into the lower to mid 50s, except cooler by the lakeshore.

Cronce

SHORT TERM

Issued 1130 PM CDT Sun Apr 19 2026

Today through Tuesday night:

Lows this morning in the mid 20s to low 30s combined with calm winds and clear skies will allow for widespread frost development this morning, burning off shortly after sunrise. High clouds are expected to move in by the afternoon hours, with south- southwesterly winds increasing through the day as high pressure exits to the southeast and low pressure propagates through northern Manitoba. Gusts around 20 mph are expected, with highs in the low 50s. Temperatures overnight are only expected to dip into the low 40s, as southwesterly winds continue.

A weak frontal boundary from the northern low will propagate through southern Wisconsin Tuesday morning. A few showers are possible across far southern Wisconsin as the front stalls, but confidence is low with plenty of dry air in the 700 mb to surface layer. Majority of this precipitation would evaporate before reaching the ground. Expecting highs in the 70s as southerly winds continue. A lake breeze may contribute to highs in the mid 60s near Lake Michigan. Tuesday evening, the cold front from the northern low will sweep through southern Wisconsin from northeast to southwest. Expect lows in the mid 40s to upper 30s, with the lowest temperatures in the Sheboygan/Fond du Lac areas.

MH

LONG TERM

Issued 1130 PM CDT Sun Apr 19 2026

Wednesday through Sunday:

Second half of the week will be a warm one. Temps quickly recover on Wednesday as the the upper-level ridge axis works its way across the region. Given the high probabilities (+80%) from the GEFS, ENS, and GEPS, expect daytime temps to warm back into the 70s for Wednesday and even a potential for upper 70s and maybe even crack 80F on Thursday. However, any easterly wind off of Lake Michigan will keep things several degrees cooler along the lakeshore to the Kettle Moraine, while further inland will likely see the warmest temps. Overnight temps are also looking milder for this time of year ranging from upper 40s to lower 60s through the end of the week.

Accompanying this warm stretch will be another potential for showers and thunderstorms as an upper-level trough swings across the the Northern Plains and Upper Mississippi River Valley for Thursday into Friday. The long range models continue a trend pivoting the mid- level trough back northward as another trough tries to phase with it. Given this trend, expect to see the surface low follow suit and likely track across the Dakotas and lift into Manitoba/northwestern Ontario later Thursday. While southern WI will be on the warm side of this system with instability building toward 1000J/kg, the better upper-level forcing along with more favorable shear looks to remain to the west-northwest close to the center of the low itself. Thus, the more favorable setup for severe thunderstorm activity looks to remain along and west of the Upper Mississippi River Valley at this time. May see the decaying remnants of this activity work its way into the western half of the area later Thursday. While there is fairly consistent agreement on the long-range ensembles as well as the ML severe probs for things to remain just outside our area, we are still several days out and will be monitoring for any eastward shift in the trends.

Friday is trending warmer, but the cold front associated with the Thursday system is progged to gradually work its way across southern WI through the day. This will bring cooler airmass to the region for the weekend under mainly zonal upper-level flow. However, not expecting as cold of temps as we saw with this past weekend system, but generally looking at temps closer to normal.

Wagner

AVIATION

Issued 758 AM CDT Mon Apr 20 2026

VFR conditions through the period. Breezy southerly winds will persist through the night, but expect low level wind shear as SW 40 to 50 kt winds will persist just above the surface.

Cronce

MARINE

Issued 758 AM CDT Sun Apr 19 2026

High pressure of 30.4 inches shifting over Lower Michigan today and low pressure around 29.7 inches developing in the Plains will bring increasing southerly winds to Lake Michigan through Tuesday morning.A few gales are possible tonight into early Tuesday morning, especially over the northern third of the lake as low pressure around 29.5 inches also progresses across the Hudson Bay. A cold front from this low will progress southward through the lake Tuesday afternoon and evening, shifting winds to northeasterly. High pressure around 30.4 inches builds into Ontario on Wednesday, bringing light and variable winds. Winds will then become southeast and increase Thursday into Friday as strong low pressure around 29.2 inches develops in the northern Plains.

Increasing southerly winds with gusts up to 25 kt will build high waves in the nearshore areas north of Port Washington this afternoon. A Small Craft Advisory is in effect.

Cronce

MKX WATCHES / WARNINGS / ADVISORIES

WI...None. LM...Small Craft Advisory...LMZ643...4 PM Monday to 7 AM Tuesday.