textproduct: Milwaukee/Sullivan

KEY MESSAGES

- High temperatures remaining 10 to 20-plus degrees above normal through Thursday

- Widespread round of showers and isolated thunderstorms (a 50 to 90 percent chance) expected tonight. Isolated small hail cannot be rule out with any thunderstorms.

- More precipitation expected Thursday afternoon into Friday, with rain gradually mixing with and switching over to light snow

- Temperatures trending back toward normal by the weekend

UPDATE

Issued 545 PM CST Tue Feb 17 2026

Overall not too much change from the prior forecast other than chasing the cooling temps along the lake front with milder temps inland. These cooler temps may also contribute to seeing precip develop and reach the surface given the lower dewpoints with the onshore, moist flow off of Lake Michigan. Meanwhile still looking mostly dry across southwestern WI this evening and tonight. PoP timing remains on track given the latest CAM runs with an initial round late this early, but additional chance when the better forcing arrives overnight into early Wednesday morning. Still cannot rule out seeing a few taller showers be able to tap into some meager (250-500 J/kg) of elevated instability and produce a few isolated rumbles of thunder and potential some small hail tonight, but chances and impacts remain on the lower side.

Wagner

SHORT TERM

Issued 1259 PM CST Tue Feb 17 2026

This Afternoon through Wednesday night:

A broad upper trough that pushed onshore of the western U.S. this morning will bring a little more active weather pattern to the Upper Midwest for the next few days. The first wave rounding the base of the trough into CA early this morning is rapidly trekking across the Intermountain West today. The resultant surface low developing in the Northern Plains will become compact and deepen over the Dakotas this evening and then stall over northern MN as it occludes Wednesday morning and gradually weaken through the day.

Strong warm air advection will drive our weather in southern WI this evening through Wednesday morning. Expect scattered showers and thunderstorms with small hail possible overnight. Overall, the better synoptic forcing may be disjointed from the better instability and moisture since the system will begin occluding as the low reaches central MN around midnight. However, the 12Z models are starting to suggest some better alignment with a later arrival of the occlusion and mid level trough. Weak mid level vorticity advection and 700mb frontogenesis will arrive in southern WI during the early evening hours prior to 9 PM. The low levels will be dry during this time, but the strong mid level forcing should help the precip start to saturate from the top down. Less confidence in rain reaching the ground until after 9 PM, especially over southwest WI. Instability will be limited with this first surge of synoptic forcing, with model soundings showing tall, skinny CAPE and a lot of dry air to overcome.

The better forcing will arrive into southwest WI around midnight with the main mid level shortwave trough, left exit region of the upper jet, and the nose of the low level jet. The 12Z GFS really delayed the arrival of this compared to the 06Z run. The 12Z NAM still keeps an earlier arrival time of the LLJ (prior to midnight, thus disjointed). The system will quickly occlude after midnight, with the low level jet veering over IL and IN, but this is when the elevated, most unstable CAPE arrives with values up to 250 j/kg.

Thus we have a brief window where we could get some elevated hail over south central and east central WI during the early morning hours. This is not a great setup for severe hail with the limited instability and moisture (although bulk shear is over 40kt), but with the February cold temps, small hail at times is quite probable.

Dry air will quickly push into southern WI Wednesday morning, cutting off all precip chances and giving us sunshine by late morning. Gusty westerly winds up to 35 or 40 mph are expected. Temperatures will continue to be mild with highs in the upper 50s to lower 60. Very dry air and deep mixing will bring RH levels to very low values leading to minor fire weather concerns. Fuels are not quite dry enough for headlines.

Cronce

LONG TERM

Issued 1259 PM CST Tue Feb 17 2026

Wednesday Night through Tuesday:

Winds will diminish quickly Wednesday evening as we decouple with brief high pressure overhead. With the dry air in place, lows will dip into the mid 30s, with areas toward central WI falling below freezing. Meanwhile, that occluded low will sit over far northwest WI and continue to weaken during the overnight hours. Southern WI will remain within the warm sector.

The next shortwave trekking across the Plains will create another potent surface low Thursday morning, this time over northeast KS. That low will track across northern MO and northwest IL during the day Thursday while undergoing cyclogenesis, and then land over southern WI Thursday evening. Southern WI should see scattered rain showers out ahead of this system with the warm front and vorticity advection Thursday afternoon and evening. The cold front will push through southern WI from west to east overnight Thu nt into Fri morning. Precip should change to all snow during this time and we are expecting minor snow accumulation. Each model has this surface low taking a slightly different track, with differing degrees of the cold air advection behind it. This is typical with occluding lows, and since this one will be occluding right over us, we will need to keep an eye on things and be prepared for the forecast to change right up to the time it is occurring.

Several additional shortwave troughs are expected to track across the Upper Great Lakes over the weekend and the pattern looks chilly, intermittently breezy, and with chances for flurries at times. For the first part of next week, broad ridging over the center of the country will encourage shortwaves to track across the northern Plains. This will put WI in a favorable spot for active weather for Tue-Wed, with precip type uncertain.

Cronce

AVIATION

Issued 545 PM CST Tue Feb 17 2026

Will see east to southeast winds pick up through the evening as low pressure approaches from the Dakotas. Dry air ahead of this system will limit rain chances this evening and result in virga for southwestern WI. However, easterly flow off of Lake Michigan may create better chance for rain to reach the surface further east this evening. Another round of showers and even a few rumbles of thunder along with potential for some small hail cannot be ruled out overnight with the arrival of better forcing along the weak frontal boundary. Again areas southwest WI will have lower chances given the battle between saturation and drier air, but may still see some showers with the overnight round.

Accompanying the precip chances will be lower ceilings and visibility. Generally looking at widespread MVFR into early Wednesday morning, but lower flight conditions may be possible with any moderate shower/storms, especially for southeast and east central WI. Drier air will then quickly move into southern WI from the southwest between 09z-13z, with conditions improving through daybreak. Lower flight conditions may hang on a bit longer for the eastern terminals, but gradually clear through the morning. Otherwise, will see VFR condition and increasing gusty westerly winds up to 35kt through the late morning and into the afternoon. Then winds will diminish after sunset Wednesday evening.

Wagner

MARINE

Issued 1259 PM CST Tue Feb 17 2026

East to southeast winds will increase today into tonight as strong, compact low pressure of 29.1 inches approaches from the Dakotas. High-end, easterly gales are expected from midnight into Wednesday afternoon over the northern third of the lake, where a Gale Warning remains in effect. The warmer airmass over the chilly lake waters should limit the mixing down of higher gusts elsewhere across the lake.

A Small Craft Advisory goes into effect this afternoon for the nearshore areas of southeast WI due to onshore winds building high waves. Winds will shift to the south early Wednesday morning, and then westerly wind gusts up to 30 kt, especially closer to the shoreline, will develop by late Wed morning and persist until late Wed afternoon.

Winds will ease later Wednesday into Thursday and become southerly as that low occludes and weakens to 29.5 inches over northern Minnesota. Winds will increase Thursday night into Friday night as another strong low pressure system around 29.2 inches tracks from Iowa into central Wisconsin. That low will cross northern or central Lake Michigan Friday morning and gradually weaken through Saturday. Gusty northerly winds are expected Sunday into Monday.

Cronce

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...Gale Warning...LMZ261-LMZ362-LMZ364-LMZ563...midnight Wednesday to 4 PM Wednesday.

Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 3 PM Wednesday.