textproduct: Milwaukee/Sullivan

KEY MESSAGES

- 15% percent chances for light rain showers today, with breezy northwest winds this afternoon. - Below normal temperatures return for Sunday and Monday with additional Frost Advisories possible over portions of srn WI. - A clipper system brings high rain chances (80 percent) for Tuesday. A few thunderstorms will be possible but no severe storms are anticipated at this time.

SHORT TERM

Issued 1200 AM CDT Sat May 9 2026

Today and Tonight:

Broken altocumulus clouds will linger aloft through the overnight hours, with plenty of dry air in the Residual Layer beneath and some virga evident on radar. 850-700mb WAA and loosely organized FGEN may manage to produce some brief sprinkles of rain out of this activity through the overnight hours, but precip chances are capped at ~15% or less.

A cold front crosses the region early this morning, with breezy northwest winds arriving behind it later this morning through this afternoon. Some 20-30 MPH gusts can be expected, stronger gusts to ~35 MPH cannot be ruled out. Daytime high temps in the 60s to around 70 across the region today, with the synoptic breeze spreading the warmth all the way through the shoreline. An axis of open cellular light rainshowers may develop in the wake of the cold front today, aided by some 500mb PVA. But, similar to the ongoing altocumulus / virga, it's likely to evaporate before reaching the ground, leaving only ~15% or less rain chances.

Northwest winds decelerate and sky cover decreases tonight, with some slight potential for frost development towards the northwest corner of the CWA (towards central WI, low temps in the mid 30s), likely too warm elsewhere.

Sheppard

LONG TERM

Issued 1200 AM CDT Sat May 9 2026

Sunday through Friday:

High temperatures around 60 degrees expected Sunday, with a redeveloping NW breeze. Some potential for a lake breeze to push against this synoptic flow and hold shoreline temperatures to the low/mid 50s, though our current forecast spreads 60 degree highs right up towards the shoreline. Dry weather looking likely as high pressure builds in from the northwest. Potential for frost in inland areas Sunday night, particularly in the northwestern corner of the CWA towards central WI (lows in the low to mid 30s). Calm winds and clear skies looking likely.

High pressure passes overhead Monday with temperatures holding steady (around 60) for inland areas. The weak synoptic wind flow will allow a healthy easterly lake breeze to form, likely holding shoreline high temps to the low 50s. Dry weather continues.

A clipper system will track eastward across the region on Tuesday, delivering 80% rain chances. The majority of model QPF falls during the daytime hours regardless of whether the low tracks through southern WI (08.12z ECMWF) or lake superior (08.18z GFS), with precip chances arriving from the west as early as predawn Tuesday and exiting east as late as Tuesday evening (the precip would only last a small fraction of that window in any case). There will be chances for thunderstorms at times (particularly Tuesday afternoon), but strong to severe storms are not looking likely given the difficulty of a fast-propagating clipper system trying to draw sufficient gulf moisture and build instability. That said, the odds of reaching or exceeding 500 joules CAPE on the GEFS has increased to 40-50% over southwestern WI, and at least 3 of 30 viewable ensemble members approach 1000 joules somewhere in the region, hence we're not completely in the clear yet. The intensity, propagation speed, and track of the clipper system will be monitored.

Dry weather expected Wednesday as high pressure tracks through the region behind the departing clipper system. Ridging in the jet stream is expected to gradually build into the Midwestern CONUS through late next week, yielding a warming trend. As seen on the CPC 6-10 and 8-14 day temperature outlooks, the ridging and warming trend are likely to intensify through the end of this forecast discussion period and beyond.

Sheppard

AVIATION

Issued 1200 AM CDT Sat May 9 2026

Broken altocumulus clouds around 10,000 ft continue eastward across the region through the predawn hours, exiting east. Only ~10-15% chances for any rain from that activity, mostly virga due to dry air beneath the cloud bases. Same story for the additional altocumulus (at a similar altitude) behind the cold front late this morning through this afternoon. Can't rule out a brief spit of rain, but ceilings / visibility should remain VFR.

Some marginal LLWS through the predawn hours with light southwesterly surface winds and ~35kt WSW winds at 2,000 ft AGL. Currently leaving this out of the TAFs as it is below criteria. Surface winds veer NW behind the cold front later this morning and become gusty into the afternoon (20-25kt gusts, possibly upwards of 30 kt at times). Winds and gusts subside this evening. A weak backdoor cold front may lead to some light northeast winds for shoreline terminals tonight. Dry weather and VFR expected to continue.

Sheppard

MARINE

Issued 1200 AM CDT Sat May 9 2026

Low pressure around 29.6 inches along the Minnesota and Canadian border will move east across Lake Superior through the rest of the overnight hours. Its cold front will move across Lake Michigan this morning. Breezy south winds continue overnight ahead of the front, veering west and decelerating as the front crosses later this morning. Gusty northwest winds develop over Wisconsin this afternoon behind the front, which may encroach into the western nearshore waters (a few 20-30kt gusts possible), but will decelerate towards the open waters. Another (backdoor) cold front will sag southwards across the lake late today through tonight, with a brief period of north winds behind it.

High pressure around 30.3 inches is then expected to move from southern Manitoba on Sunday to over Lake Michigan by Monday afternoon. Relatively light and variable winds are expected early next week.

Sheppard

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...None.