171
FXUS63 KMKX 120916
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
416 AM CDT Mon May 12 2025

.KEY MESSAGES...

- Above normal temperatures continue through the first half of
  this week.

- Scattered (20 to 50 percent chances) showers and storms are
  possible during the afternoon hours on Tuesday and Wednesday.

- Better chances for showers and thunderstorms (35 to 60 percent
  chances) arrive along a cold front Thursday afternoon and
  evening. A few storms could be strong to severe.

- Additional isolated to scattered (20 to 40 percent chances)
  showers linger Friday.

- Cooler temperatures settle into southern Wisconsin Friday into
  the weekend.

&&

.SHORT TERM...
Issued 416 AM CDT Mon May 12 2025

Today through Tuesday:

Quiet weather will continue today under high pressure. High
clouds are likely to move in from the south today in advance of
approaching low pressure. Above normal temps are expected today
most places, except for near normal conditions near the lake.

The broad upper low and associated weak surface low will
continue to approach from the south tonight into Tuesday. This
will bring increasing moisture into southern Wisconsin, along
with a chance for showers and a few storms. The best chance for
showers and storms will be during the afternoon hours Tuesday,
as daytime heating will kick off some convection. Onshore winds
will limit activity in the east due the the more stable airmass
from the cooler lake. Showers should wind down by early evening
as daytime heating is lost. Nudged high temps down a bit Tuesday
due to higher confidence in mostly cloudy conditions much of
the day.

DDV

&&

.LONG TERM...
Issued 416 AM CDT Mon May 12 2025

Tuesday night through Sunday:

Deterministic and ensemble guidance continues to bring the closed
500 mb low centered over Kentucky Tuesday evening northeastward
and opens up into more of a trough on Wednesday. Continued chances
(20 to 35 percent) for showers are forecast, with the better
chances Wednesday with daytime heating. Weak but steady southeast
winds should bring higher dewpoints into the 50s to perhaps lower
60s by Wednesday afternoon, so it will feel more humid and allow
for increasing mean layer CAPE and some thunderstorms to occur.
Weakly sheared environment may allow for some hail and brief gusty
winds Wednesday afternoon.

Ensembles continue to suggest that the warm period of
temperatures linger through Thursday across the area, as an
anomalous 500 mb ridge shifts east of the Great Lakes region.
Highs should exceed 80 degrees Fahrenheit across inland areas for
Wednesday, with onshore winds keeping lakeshore areas cooler.
Small spreads in the ensemble guidance indicate a relatively high
confidence (greater than 70 percent) in these warm temperatures
occurring.

The warmest day appears to be Thursday, with middle 80s expected
inland and perhaps upper 80s with enough sunshine. Humid
conditions with dewpoints into the lower 60s will linger. Still
looks cooler near the lake with southeast winds. There may be some
low clouds and fog over and near the lake at times Tuesday night
into Thursday, with the higher dewpoints over the cool lake
waters.

A closed and deepening 500 mb low should shift east northeastward
across the northern Plains into the Western Great Lakes region
Thursday into Friday. There looks to be a negatively tiled
shortwave trough with this 500 mb low that shifts northeast across
the region Thursday afternoon and evening. This should help bring
a cold front northeast through the region Thursday or Thursday
night. There is some uncertainty in the timing of these features.

This should bring a better chance (40 to 60 percent) for more
organized showers and thunderstorms, as supported by increasing
numbers of ensemble members with measurable precipitation from the
ECE/GEFS. There should be more robust mean layer CAPE and bulk
shear values as well, so there look to be strong to severe storm
potential along and ahead of the front. Machine learning models
continue to indicate severe potential during that period across
the region with the frontal passage. SPC has the area in 15
percent severe probabilities for Thursday into Thursday night, so
will need to continue to monitor and possibly start messaging this
potential.

Gusty southwest winds may occur after the front moves through
Thursday night and linger into Friday, as the main 500 mb low
shifts across or just north of the area. A secondary cold front
may pass through the region Friday or Friday night/Saturday, with
continued chances (20 to 30 percent) for showers and perhaps a
few thunderstorms. Trends in this period are more uncertain, but
ensembles are still showing some members with measurable
precipitation. Temperatures look to drop to more seasonable values
Friday into next weekend per ensemble trends.

Wood

&&

.AVIATION...
Issued 416 AM CDT Mon May 12 2025

Quiet weather will continue today under the influence of high
pressure exiting to the east. Light southeast winds will prevail
most places, with winds more easterly near the lake. High
clouds are expected to move in from the south through the day.
There may be a few showers by later tonight, as low pressure
approaches from the south. A few models are also suggesting the
potential for some lower clouds later tonight into Tuesday. Not
out of the question for some reduced visibilities in the east
as well, given increasing low level moisture and onshore winds
off the chilly lake.

DDV

&&

.MARINE...
Issued 416 AM CDT Mon May 12 2025

South to southeast winds across the lake today should become more
east to northeast across the southern half of the lake, as high
pressure around 30.3 inches remains well east of the region.
Winds should then become southeast across the entire lake tonight,
shifting to the east Tuesday into Wednesday, as weak low pressure
around 29.8 inches approaches southern Lake Michigan from the
Ohio Valley. A few thunderstorms are also possible during this
period, mainly over southern portions of the lake.

There may be some fog over the lake at times Tuesday night into
Thursday, with the higher dewpoints moving over the cool lake
waters.

A larger area of low pressure around 29.4 inches will form in the
northern Great Plains Wednesday night, crossing over or north of
Lake Superior Thursday night or Friday. This will lead to
increasing southeast winds across the open waters through
Thursday afternoon. Gales are not expected at this time, though
trends will be monitored in the coming forecasts. Small Craft
Advisory conditions may occur for the nearshore waters Thursday
into Thursday evening.

More widespread thunderstorm potential will accompany the passing
low and cold front, with the best chances Thursday evening and
night. Some storms may become strong to severe during this period.
Gusty southwest winds behind the front Friday into Friday night
may occur, becoming west on Saturday. It is too early to tell if
gales are possible during this period, but Small Craft Advisory
conditions may occur for the nearshore waters.

Wood

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&

$$

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