809
FXUS63 KMKX 170825
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
325 AM CDT Sat May 17 2025

.KEY MESSAGES...

- Light sprinkles & rain showers (~15-40% chances) continue
  through this morning, particularly along and north of
  I-94/US-18.

- Below-normal high temps continue today through the middle of
  next week.

- Periods of showers and isolated thunderstorms (generally
  ~25-60% chances) return Monday through Wednesday ahead of the
  next disturbance, with the best potential over southwest and
  south- central Wisconsin.

- High temperatures rebound back toward normal by the end of the
  next week.

&&

.SHORT TERM...
Issued 328 AM CDT Sat May 17 2025

Today through Sunday Night:

Synopsis/Mesoanalysis: Upper low pressure continues to linger across
the western Great Lakes this morning, leaving most of the state
under mostly cloudy skies. A shortwave is pivoting around the
southwest flank of the upper low, with GOES water vapor imagery
placing the feature over the Black River Falls vicinity as of 3 AM.
Lift along/ahead of the shortwave has encouraged scattered sprinkle
and shower development, with a scattering of stations from the
Wisconsin River Valley to Stevens Point reporting light rain. The
aforementioned shortwave will continue to pivot east this morning,
bringing additional rain shower chances to areas primarily along and
north of I-94 & US-18. Conditions will dry out this afternoon as the
shortwave & its parent upper low pull east into the Saint Lawrence
Valley. High pressure will build into the region tonight through
Sunday, bringing partly cloudy skies and lighter surface winds.
Currently moving onshore the Oregon Pacific coast, the next
disturbance will shift through the Great Basin & central Rockies
today/tonight, ultimately ejecting into the Central Plains Sunday
afternoon. The feature`s ejection will encourage widespread shower
and thunderstorm development in the Central Plains Sunday afternoon,
with activity attempting to advance toward southwest Wisconsin in
its decaying stages during the predawn hours Monday. Current
expectations are that this precip will remain southwest of the
region, though trends will continue to be monitored.

Today: Showers will linger through this morning. Best potential will
focus to the north of I-94 and US-18, where proximity to the passing
shortwave will be greatest. Despite greater distance from the
passing shortwave, an isolated shower or sprinkle can`t be entirely
ruled out further south, where slight chance precip probabilities
have been maintained in the overnight update. Conditions will dry
out this afternoon, with continued brisk winds making it feel
noticeably cooler relative to previous days.

Sunday: With high pressure moving into the western Great Lakes, more
sunshine is anticipated. This should result in milder high
temperatures relative to today across most of southern Wisconsin,
though much weaker synoptic flow will allow the lake breeze to
quickly mix inland during the afternoon hours. Thus anticipate
relatively wide west-east spread in high temperatures Sunday
afternoon, with readings in the 60s along/west of I-41 and 50s
further east.

Sunday Night: Decaying showers/thundershowers will attempt to
advance toward southwestern Wisconsin during the predawn hours, but
will struggle to maintain themselves as they encounter antecedent
high pressure. Have thus maintained a completely dry forecast in the
overnight update, but will continue to monitor trends.

Quigley

&&

.LONG TERM...
Issued 328 AM CDT Sat May 17 2025

Monday through Friday:

There is some uncertainty during this period as extended models have
some timing and placement differences with the upper low and
associated sfc low that will move ewd across the central USA.
Initially expect a dry enely sfc flow emanating from a large Hudson
Bay high pressure area to hold back rain for Monday.

Low pressure will then track from the central Great Plains to srn IA
or nrn MO by 12Z Tue as an upper wave rotates around the upper low.
The upper low will then track into IA on Tue and nrn IL Tue nt while
the sfc low moves toward the Ohio River Valley. Thus lift and
moisture will be sufficiently close for rain (60-80 percent) Tue-
Tue nt, but lesser chances (40-50 percent) toward central WI.
As the low moves to the ern Ohio River Valley, occlusion may occur
and retrograde over srn Ontario and surrounding areas. This will
impact whether high pressure and pleasant wx returns for Thu-Fri or
is delayed. The NBM rainfall amounts at this time range from a
quarter inch over central WI to an inch near the IL border with
shifts to the north or south highly probable.

Gehring

&&

.AVIATION...
Issued 328 AM CDT Sat May 17 2025

A mixture of VFR and MVFR flight categories prevail early this
morning as low pressure lingers over the Upper Peninsula of
Michigan. Affiliated with an approaching disturbance, light -SHRA
and -DZ has been observed at MSN and at stations in the Wisconsin
River Valley. Precip has been accompanied by lowered CIG readings,
with several sites west of MSN reporting MVFR as of midnight. The
aforementioned disturbance will continue to progress across southern
Wisconsin this morning, bringing reduced CIGs & possible
precipitation to all aerodromes. Have accounted for potential precip
with PROB30 and TEMPO groups at MSN and SBM, where forecast
confidence is highest. The lowered CIGs will result in reduced
flight categories by sunrise at all fields. Expect mostly MVFR
reductions, but will be monitoring for brief periods of IFR,
particularly in the vicinity of MSN and SBM. -SHRA and -DZ will
conclude this afternoon as the upper disturbance pushes east.
Anticipate improvements to VFR in the wake of departing precip,
particularly at southern terminals. Have inserted prevailing VFR
back into the forecast near the end of the period at SBM, though
some model guidance suggests that MVFR categories could struggle to
dissipate. Will thus be monitoring trends for potential amendments
in the coming forecasts. Currently gusty west-southwest winds will
weaken & shift out of the west-northwest tonight as high pressure
builds in from the Northern Plains.

Quigley

&&

.MARINE...
Issued 328 AM CDT Sat May 17 2025

Breezy west-southwest winds continue across Lake Michigan this
morning as 992 mb low pressure lingers near the northern open
waters. Breezy conditions will continue through today as the
aforementioned area of low pressure migrates toward the Ontario-
Quebec border. Wind directions will turn west-northwesterly tonight
as 1030 mb high pressure moves toward the Hudson Bay vicinity. The
approach of this area of high pressure will allow winds to taper
during the second half of the overnight hours tonight. Winds will
turn due northerly during the day on Sunday as high pressure pivots
into far northern Ontario.

Wind speeds will increase during the day on Monday as 1032 mb high
pressure lingers over the Hudson Bay vicinity and 998 mb low
pressure forms in the central Great Plains. Brisk winds will
continue into the day on Tuesday, shifting east-northeasterly as the
aforementioned area of low pressure moves into the Ohio River Valley
during the afternoon hours. The low will move into the Appalachian
Mountains on Wednesday, resulting in a northerly wind shift across
Lake Michigan. Given that low pressure will be approaching and
passing to the south of the open waters, winds will be gusty on both
Tuesday and Wednesday. Gales are not anticipated at this time,
though trends will continue to be monitored in the coming forecasts.
The approaching low will also bring chances for showers and isolated
thunderstorms, with severe weather not expected. Winds will
gradually taper Thursday into Friday, when 1022 mb high pressure is
forecast to settle into the western Great Lakes.

Gusty winds continue in nearshore zones into the first half of this
evening, when conditions will begin to taper from south to north.
Given the south-north delay, have thus elected to extend the Small
Craft Advisory through 10 PM CDT from North Point to Sheboygan. The
Small Craft Advisory will expire as scheduled at 7 PM CDT further
south. Winds will be lighter on Sunday as high pressure builds into
the Northern Plains. Both wind gusts and wave heights will increase
ahead of approaching low pressure Sunday night, resulting in the
return of Small Craft Advisory conditions by early Monday morning.
Anticipate that gusts and waves will remain elevated through at
least mid-week, resulting in a prolonged period of hazardous
conditions through Thursday morning. Will address the prolonged
period of impacts with an additional Small Craft Advisory in later
forecasts.

Quigley

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643-LMZ644 until 10 PM Saturday.

     Small Craft Advisory...LMZ645-LMZ646 until 7 PM Saturday.

&&

$$

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