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Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
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FXUS63 KMKX 250930
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
430 AM CDT Thu Apr 25 2024

.KEY MESSAGES...

- Freeze Warning until 8 AM CDT this morning for below-freezing
  temperatures.

- Active pattern later Friday through this weekend. Multiple
  rounds of showers/storms will result in locally heavy
  rainfall. There is a severe storm risk as well, with some
  uncertainty remaining.

&&

.SHORT TERM...
Issued 430 AM CDT Thu Apr 25 2024

Today through Friday:

The Freeze Warning remains in effect until 8 AM CDT this morning
for the entire forecast area. High clouds moving through the
area overnight have limited the temperature drop in the western
parts of the area, with at or below freezing temperatures in the
east. There are some breaks in the clouds, and with the very
light to calm winds, some areas in the west should still drop to
or a little below freezing.

High pressure will continue to move east of the region today and
tonight. The high will bring quiet weather to the area, with
light east to southeast winds. Skies should become mostly sunny
by the afternoon. Highs should reach the upper 50s to lower 60s
well inland, with onshore winds keeping upper 40s to middle 50s
closer to Lake Michigan.

Southeast winds should gradually increase tonight, with middle
to high clouds gradually moving into the area. May still see
some middle 30s for lows in northern and northeastern parts of
the area.

The breezy southeast flow in the low levels continues into
Friday, as the low pressure system develops in the Central
Plains. This flow is rather dry, so it may take awhile on Friday
for the initial round of warm air advection and low level jet-
fed showers and thunderstorms to move into the area. Slowed down
the timing of the precipitation to mainly the afternoon hours,
and may need more adjustments for a slower start toward sunset.
Highs should reach the middle 50s to around 60.

Wood

&&

.LONG TERM...
Issued 430 AM CDT Thu Apr 25 2024

Friday night through Wednesday:

Deterministic models and ensembles suggest the surface low
tracking northeast into southern Minnesota Friday night, then
into Lake Superior on Saturday. There is good agreement with
showing a period of showers and elevated thunderstorms shifting
northeast through the area with the warm frontal passage Friday
night and early Saturday. The low level jet will point into the
area and help feed the warm and moist air into the region.

Not out of the question to see some elevated storms produce
hail, with forecast soundings showing decent elevated CAPE
within some strong effective layer shear. This activity should
move northeast of the area by middle morning, with a break in
the precipitation possible into Saturday afternoon. This will
allow warm and moist air into the area, with highs well into the
70s and dew points possibly reaching 60 or higher.

The low will bring a cold front into north central and southwest
Wisconsin by 00z Sunday, possibly sagging southeast into the
area Saturday night, before the next low moving toward the
region has the boundary possibly stalling out somewhere across
southern Wisconsin. Another low level jet feed from the south
southwest may feed into the area and interact with this boundary
to produce more widespread showers and thunderstorms.

Forecast soundings show strong deep layer and low layer shear,
with warm and moist air bringing mean layer CAPE values well
above 1000 J/kg. Thus, the later Saturday into Saturday
night/early Sunday morning period may be the first possibility
for strong to severe storms. SPC Day 3 Outlook as the area in a
slight risk, which seems reasonable. Mesoscale details will
determine what ultimately occurs, as far as storm mode and areal
coverage, so keep up with the forecast.

This will also be a chance for heavy rainfall and possibly some
training convection, with the 500 mb flow parallel to the
surface boundary. A solid 1 to 2 inches of rainfall may occur
through Saturday night/early Sunday morning, which is the 25th
and 75th percentiles of NBM, respectively. There is still
uncertainty with the rainfall amounts, so keep up with this
portion of the forecast.

A second low track, similar to the first low track, should move
northeast through the region Sunday into Monday, with the
forecast area in the warm sector once again. Another round of
showers and thunderstorms may occur with the lingering stalled
frontal boundary into Sunday, before it tries to shift north.
Warm and moist air will linger on Sunday.

If it can, then the trailing cold front or a pre-frontal trough
could help focus more strong to severe storms later Sunday into
Sunday night. The timing of the cold front is toward 12Z Monday
or later, which is not ideal for severe storms. Thus, more
uncertainty exists in this period for what may occur. Strong
deep layer shear and enough mean layer CAPE are there, so there
is severe potential.

Heavy rainfall in this period would add to those rainfall
totals, and perhaps some impacts if training convection occurs.
NBM shows up to a 50 percent potential for greater than 2 inches
of rainfall occurring through the weekend in western parts of
the area.

Things should quiet down Monday afternoon or evening after the
low exits the region. May see another low move into the region
by the middle of next week, with more chances for showers and
storms. Ensembles indicate warm temperatures should linger into
next week.

Wood

&&

.AVIATION...
Issued 430 AM CDT Thu Apr 25 2024

High clouds will move through the area into this morning, before
clearing out with mostly clear skies this afternoon into this
evening. Some more high clouds should move in later tonight into
early Friday.

Light and variable winds into this morning will become southeast
and remain relatively light into this afternoon. Some southeast
gusts may occur for terminals near the lake, as the lake breeze
pushes westward. Southeast winds should then increase and tonight
into Friday morning.

Wood

&&

.MARINE...
Issued 430 AM CDT Thu Apr 25 2024

Light winds generally from the southeast will prevail over Lake
Michigan today, as high pressure around 30.1 inches gradually
shifts to the east of the region. Southeast winds will begin to
increase tonight.

Low pressure of 29.2 inches will develop across the Central
Plains on Friday and move northeast into Lake Superior on
Saturday. Southeast winds will continue to strengthen Friday
into Friday night, becoming south on Saturday. Some gales are
possible at times Friday night into Saturday over the open
waters. Showers and thunderstorms are expected at times across
the region late Friday into Saturday night.

Another low pressure system around 29.5 inches will move
northeast across the Great Lakes region Sunday into Monday,
which will again bring gusty south winds across Lake Michigan.
Showers and thunderstorms are expected at times once again
during this period.

A Small Craft Advisory is in effect from Friday through Monday,
for southeast winds building to 15 to 25 knots later tonight
into Friday night, becoming south Saturday into Monday. Gusts to
30 knots are expected at times. Waves building to 3 to 5 feet
are expected Friday, then 4 to 7 feet Friday night into
Saturday, then 2 to 4 feet Saturday night into Monday.

Wood

&&

.FIRE WEATHER...
Issued 430 AM CDT Thu Apr 25 2024

One more day of very low relative humidity values are expected
away from Lake Michigan, where values of 20 to 30 percent should
occur. Winds are expected to become southeast by later this
morning and remain relatively light this afternoon. There may
be some gusts near Lake Michigan in the afternoon with the lake
breeze.

Showers and thunderstorms should gradually move northeast into
the area Friday afternoon, with rounds of showers and storms
through the upcoming weekend. Warmer temperatures and more humid
conditions are expected, along with gusty southeast to south
winds.

Wood

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Freeze Warning...WIZ046-WIZ047-WIZ051-WIZ052-WIZ056-WIZ057-
     WIZ058-WIZ059-WIZ060-WIZ062-WIZ063-WIZ064-WIZ065-WIZ066-
     WIZ067-WIZ068-WIZ069-WIZ070-WIZ071-WIZ072 until 8 AM
     Thursday.

LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646...7 AM
     Friday to 7 PM Monday.

&&

$$

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