642
FXUS63 KMKX 141527
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1027 AM CDT Wed May 14 2025

.KEY MESSAGES...

- A Marine Dense Fog Advisory is in effect for all open waters
  of Lake Michigan and all nearshore waters adjacent to
  Wisconsin through late Thursday afternoon. This fog may drift
  into eastern WI once again tonight through early Thursday
  morning.

- Widely scattered showers and thunderstorms inland from Lake
  Michigan are forecast again this afternoon (20 to 30 percent
  chances).

- There is a level 3 out of 5 conditional threat for severe
  thunderstorms Thursday afternoon and evening (2 PM to 10 PM
  CDT in particular). Dry air may limit storm coverage, but if
  storms form, very large hail, tornadoes, and strong wind gusts
  will be possible.

- Additional isolated to scattered (15 to 40 percent chances)
  showers and thunderstorms are possible for Friday. A couple of
  these storms may reach severe levels.

&&

.UPDATE...
Issued 1025 AM CDT Wed May 14 2025

Nearly stagnant air over Lake Michigan coupled with water
temperatures in the 40s and airmass dewpoints in the 60s is
expected to allow Marine Fog to persist, hence the extension to
the Marine Dense Fog Advisory to late Thursday afternoon.
Though no product is yet in effect, there is a signal for the
fog to return to eastern Wisconsin once again Tonight into early
Thursday morning under the influence of a weak synoptic
easterly wind. Another land-area Dense Fog Advisory may be
needed for said timeframe.

Daytime highs around 80 degrees expected inland today, cooler by
the lake. Still seeing a signal for 20-30% chances for pop up
showers and thunderstorms inland this afternoon, will hold
precip chances there unless trends warrant an increase /
decrease.

Sheppard

&&

.SHORT TERM...
Issued 249 AM CDT Wed May 14 2025

Today through Thursday:

Today will look similar to yesterday, with a broad and weak
upper low to the southeast of Wisconsin. Dewpoints around 60
degrees again will combine with the weak lift from the low and
and daytime heating to kick off isolated to scattered showers
and storms this afternoon. The best chance will be well inland
from Lake Michigan, due to a more stable airmass in the east
under onshore winds off the chilly lake. Additionally, fog and
low clouds will probably hang around east of Madison through at
least early morning today, which will also slow down daytime
heating. Will keep an eye on the progress of the fog over the
next few hours, as the advisory may need to be expanded westward
if the fog keeps advecting farther inland. High temps in the
west should get up to around 80 today, with cooler conditions
toward the lake. There is some uncertainty highs farther east
due to the potential lingering fog and clouds in the morning.

Any lingering showers this evening should wind down shortly
after sunshine with the loss of daytime heating. The main
overnight concern will be the potential for fog over the lake to
advect inland again. Latest mesoscale models do indicate a
decent chance for fog for lakeshore areas, with less of a
chance a county or two inland than what we`re currently seeing.

Not much has changed with the potential severe threat on
Thursday. Plenty of instability is expected, with at least 2000
J/kg of mixed layer CAPE by the afternoon hours. Mid level lapse
rages of 7-8 C/km and 0-6 km shear of 40-50 knots will also aid
in the severe storm potential ahead of a cold front. Latest
CAMs are showing storm development along the
temperature/moisture boundary in the western to central forecast
area between 3 and 5 pm. The line then quickly moves through per
the CAMs, exiting the east by 8 pm. One thing of note that has
been consistent in a couple of the large scale models and meso
models is the potential for the bulk of the storms to just clip
the northwest forecast area. Confidence in storm development is
higher as you go north/northwest along the frontal boundary
towards low pressure centered over the eastern Dakotas, so this
will be something to keep an eye on. If storms do develop
across southern Wisconsin though, all severe hazards will be
possible. There is plenty of time for the finer details of storm
timing and placement to change a bit, but confidence continues
to hold steady in a severe storm threat across southern
Wisconsin.

DDV

&&

.LONG TERM...
Issued 249 AM CDT Wed May 14 2025

Friday through Tuesday:

Models have trended towards a temp and moisture surge ahead of
the primary cold front on Friday, with much of the forecast area
expected to be in an unstable environment during the afternoon.
With plenty of shear still in place ahead of the low and front,
it looks like there could be a chance for additional
thunderstorms as the front moves through. Dewpoints won`t be as
high as on Thursday, so model soundings are showing a bit of an
inverted V signature, which could result in a severe wind threat
with some of the storms. The instability and solid mid-level
lapse rates also point to a hail threat. The chance for storms
may linger into the early evening, but then precip chances will
drop off quickly behind the cold front.

The main low responsible for the storm threat Thu/Fri will
finally pass by to the north Friday night into Saturday, with a
lingering rain shower chance in the north Sat. Clouds will hang
around through the day Sat as well, particulary in the north.
High pressure will then bring a return of quieter weather on
Sunday. Temperatures over the weekend will be much cooler, with
highs only topping out in the mid to upper 60s most places,
likely not getting out of the 50s near the lake on Sunday.

Forecast models continue to show a slow moving low pressure
system bringing a return of rain chances to southern Wisconsin
later Tuesday into mid-week. There are some significant
differences in strength and placement of the low among 00Z
deterministic models though, varying based on how much high
pressure centered to the east and northeast blocks the progress
of the low. In general though, this period looks like a decent
chance for cooler and wetter conditions.

DDV

&&

.AVIATION...
Issued 1025 AM CDT Wed May 14 2025

Slow southeast to east winds today, with marine fog and low
ceilings over Lake Michigan remaining in the vicinity of
lakeshore terminals, and 20-30% chances for pop up showers and
thunderstorms inland from the lake this afternoon. Other than
that, mostly VFR for inland areas for the daytime hours. The
initial development of diurnal cumulus clouds appears to be
around 2,500 ft, and may achieve a brief period of MVFR if it
achieves broken coverage (currently FEW / SCT). However, as
cumulus continue to develop, expecting them to lift over 3,000
ft.

Marine fog has the potential to drift back into eastern WI once
again tonight into early Thursday, and is likely to result in
reduced ceilings / visibilities once again. A few hrs after
sunrise Thursday the fog erodes once again.

Sheppard

&&

.MARINE...
Issued 249 AM CDT Wed May 14 2025

Dense fog will remain possible today through tonight, possibly
even hanging on into at least early Thursday, as a moist airmass
lingers over the chilly waters of Lake Michigan. The Dense Fog
Advisory over the southern two-thirds of the lake is currently
set to run until 18Z today, but may need to be extended if it
looks like the fog will indeed continue.

Winds will remain light and somewhat variable today, due to a
weak pressure gradient between developing low pressure of 29.4
inches just east of the Rockies and exiting high pressure east
of northeastern portions of the country. South to southeast
winds will then increase on Thursday as low pressure lifts
through the Northern Plains while deepening to 29.0 inches.
While breezy at times, winds are expected to remain below Small
Craft Advisory levels due to a strong inversion with the warmer
air over the cold lake. Thunderstorms will be likely along a
cold front Thursday evening, with a few strong to severe storms
possible.

Low pressure will then move through northern Minnesota and
northwest Wisconsin Friday, while weakening a bit to around 29.2
inches. Winds will remain southerly over the open waters, but
will be more southwest across the nearshore waters. Could see
gusts approach gale force over the nearshore waters ahead of the
main cold front Friday afternoon. An additional round of
thunderstorms will be possible with this secondary front, with a
few strong to severe storms possible again, especially across
the south half of the lake.

Breezy westerly winds are likely Saturday behind the cold front
and as low pressure passes by to the north. Wind gusts to Small
Craft Advisory levels look possible.

DDV

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Dense Fog Advisory...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-
     LMZ565-LMZ567-LMZ643-LMZ644-LMZ645-LMZ646-LMZ669-LMZ671-
     LMZ673-LMZ675-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-
     LMZ876-LMZ878 until 7 PM Thursday.

&&

$$

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