textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Areas of fog will linger until around midnight, when southwesterly winds are anticipated to mix the fog and raise visibility.

- The next disturbance approaches Friday night through Sunday, bringing additional precipitation to southern Wisconsin. Mostly rain appears favored at this time.

UPDATE

Issued 1026 PM CDT Wed Apr 2 2025

Areas of fog will persist over east central Wisconsin for the next hour or two before southwest winds and the passage of a cold front increase mixing and cause fog to dissipate. Otherwise, gusty winds will persist overnight as modest CAA brings steeper low to mid level lapse rates into the region overnight and cooler surface temperatures.

CMiller

SHORT TERM

Issued 130 PM CDT Wed Apr 2 2025

This Afternoon/Early Evening:

An afternoon of rapid changes is upon us as a strengthening surface low over north central IA moves to the north northeast.

An astoundingly strong mid level jet will spread over the area over the next few hours. The core of this jet is 120kt, with a broader area of 90-100 knots expanding well to the southeast. The surface low passage and mid level jet have carved an area of clearing that has spread into much of central/eastern IA.

In southern WI, we are still socked in with clouds and a surface warm front remains to our south. This warm front has been gaining some speed to the northeast with the surface low on the move into south central MN. Initially, this will bring and increase in dewpoints (low/mid 50s) with a wind shift to the southeast. Temperatures will continue to hold near dewpoints given extensive stratus and lingering showers.

Heading into the mid afternoon hours, expectations are for stratus to scatter out a bit from southwest to northeast, allowing for temperatures to rise through the 50s and into the 60s (where sunshine is observed the longest). This will aid in increasing CAPE, particularly in the low levels (0-3km). Recent CAM runs produce around 500 J/kg (give or take) for areas mainly along and south of the I-94 corridor.

As of this hour, we are seeing cumulus development over central Iowa near a pre frontal trough. This will be an area we watch very closely as the afternoon progresses as temperatures have surged into the 60s with dewpoints in the 50s. Recent HRRR runs do suggest convective initiation over the next couple of hours, moving across southern WI during the mid afternoon to early evening hours. Inheriting this activity will be our best bet for storms as initiation overhead this afternoon looks very difficult. The aforementioned mid level jet and the associated warm advection limits our mid level lapse rates considerably (closer to 5 C/km).

Storms that do enter from the west should be scattered in nature and relatively low topped. With the increasing low level lapse rates and CAPE, tapping into strong winds just above the surface is the main concern. It would not be hard to support 60mph gusts with 50kt of wind at 850mb. If supercellular characteristics can be sustained, there will be a hail and low end tornado threat. A failure point for convection that needs to be mentioned is our extreme effective shear (90+ kt). While forcing will help, CAPE looks to be meager overall and the amount of shear may be too much and storms end up being ripped apart.

Gagan

Tonight through Thursday night:

High pressure will develop directly behind the departing low moving through upper Great Lakes and into Ontario tonight into Thursday morning. While winds may initially remain breezy with the high impinging on the low the high will eventually move overhead and bring lighter west to northwest winds back to the region by Thursday afternoon. While the upper levels remain active a lack of moisture in the upper levels will keep us dry at the surface though skies may not clear out fully.

Thursday night expect quiet conditions to continue as moisture gradually slides north through the night with activity in the upper levels not expected to bring us precip until at least Friday afternoon.

Kuroski

LONG TERM

Issued 200 PM CDT Wed Apr 2 2025

Friday through Wednesday:

Another period of rain should move into at least the southeast portions of the area for Friday night, as low pressure moves northeast along a stationary frontal boundary to the southeast of the area. Leaned towards the GFS/ECMWF and EPS/GEFS track, which is mainly over northeast Illinois. The NAM is further northwest of the forecast area and appears too far to the northwest.

The best upward vertical motion may stay to the southeast of the area during this period per the EPS/GEFS, but should remain close enough to warrant leaving likely (55 to 70 percent) PoPs in the forecast for the southeast parts of the area Friday night. EPS/GEFS also show 30 to 60 percent chances for 0.10 inches of liquid precipitation or greater Friday night in southeastern parts of the area, with all ensemble members in this area showing measurable precipitation. This gives confidence in the southeast for the highest PoPs Friday night.

Cold air advection on northwest winds then occurs Saturday into Saturday night, bringing somewhat cooler temperatures into the area by Sunday.

500 mb Cluster Analysis forecasts for Sunday into Monday are mostly favoring a deep trough to develop across Ontario and Quebec, extending southwestward into the Great Lakes region. This trend should favor cold front shifting south through the area Sunday night or Monday morning. Below normal temperatures should occur during this time as well, coldest on Monday per EPS/GEFS ensemble members. The chilly temperatures should linger into Tuesday.

There is some light snow potential as well with and behind the front later Sunday night into Monday night, as differential CVA from passing vorticity maxima shift through with some low level moisture and steep low level lapse rates. Things look to dry out for Wednesday, with temperatures slowly rebounding away from Lake Michigan.

Wood

AVIATION

Issued 1031 PM CDT Wed Apr 2 2025

Expecting fog near KSBM and the immediate lakeshore to dissipate around and after 06Z as a cold front passes and drier air gest ushered into the region on southwest winds. While VFR exists easts of Madison, MVFR clouds are expected to move in overnight with the cold advection regime and linger into the first half of tomorrow. Clouds may linger through the day but raise to VFR tomorrow afternoon.

Southwest winds will persist overnight with southwest wind shear from 45 to 50 knots into the early morning hours. Wind shear should subside before dawn and gusty winds will persist into tomorrow afternoon before easing, with winds becoming WNW- erly tomorrow afternoon.

CMiller

MARINE

Issued 200 PM CDT Wed Apr 2 2025

A Gale Warning remains in effect for the entire open waters until 0z lingering longer in the far north. The surface low of 29.2 inches will progress toward Lake Superior this evening, moving into Ontario by early Thursday morning. We cannot rule out a few stronger storms across the far southern portions of the lake late this afternoon into the evening. Winds will turn southwesterly & gradually decrease in the wake of the departing surface low tonight. Gale Warning in the nearshore ends 4z with a prolonged Small Craft following it into Thursday afternoon

30.1 inch high pressure will build into the northern Great Plains Thursday afternoon, allowing winds to turn more westerly across the open waters. There is increasing potential for a period of Gales in the far north early Thursday lasting into the afternoon. Thus we have issued another Gale Warning for the northern parts of the lake from 9-19z. Winds will become light & variable Thursday night as the high crosses Lake Michigan. Winds will shift out of the northeast on Friday as low pressure forms in the southern Great Plains. Winds will increase during the day on Saturday as the low moves into the Ohio River Valley. Gales aren't forecast at this time, though trends will be monitored. Periods of rain will accompany the approaching low Friday afternoon through Saturday, with a few thunderstorms possible over far southern Lake Michigan.

Kuroski

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...Gale Warning...LMZ261-LMZ362-LMZ364-LMZ563...4 AM Thursday to 2 PM Thursday.

Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 4 PM Thursday.