996
FXUS63 KMKX 261527
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1027 AM CDT Sun May 26 2024

.KEY MESSAGES...

- Widespread showers (with a few rumbles of thunder possible)
  continue this morning into the early afternoon.

- Scattered showers and thunderstorms in the 3 PM to 8 PM
  timeframe today, with a very small potential for severe
  thunderstorms with hail and/or wind gusts along and south of
  US-18/I-94. Showers clear out later in the evening.

- Southeast winds and building waves lead to a Moderate Swim
  Risk for Lake Michigan beaches today.

- Chance for showers/storms Monday and Tuesday, particularly in
  the afternoon hours (roughly 40% chance), but quieter weather
  midweek.

&&

.UPDATE...
Issued 1025 AM CDT Sun May 26 2024

The first batch of WAA-driven rainshowers currently overspreads
most of the CWA, moving northeastward towards Sheboygan. Some
weak thunderstorms are present behind this initial line, but
said storms are likely to remain weak and elevated for the
remainder of the morning, given the southeast flow off of Lake
Michigan. Most will lose thunder potential before entering the
CWA.

Diffluent / cyclonic flow and PVA aloft, coupled with continued
850mb moist advection will allow skies to remain overcast for most
of today, preventing the sun from generating much surface based
instability. A dry slot wrapping into the low could allow for some
breaks in the clouds over far south and southwest WI in the mid
to late afternoon, but even then, it would likely be mostly
cloudy. One would expect the shortwave trough passing this
afternoon to steepen mid-level lapse rates, yet models indicate
that thermal ridging at 500mb could linger longer than
previously anticipated, further reducing afternoon
destabilization. That said, as the center of the surface low
approaches southwestern WI, the wind field will then allow the
surface low to drag the warm front into our CWA without the
stabilizing effect of Lake MI, bringing SBCAPE up to 1000
joules and MLCAPE > 500 joules to areas along and south of
I-94/US-18. The exact values / positioning of said instability
depends heavily on the exact warm frontal positioning, which is
still tough to predict, but a marginal (level 1 out of 5) risk
of severe weather is generally expected from 3 PM to 8 PM CDT
today, along and south of the I-94/US-18 corridor. Storm
strength / coverage gradually decreases later this evening,
leaving most areas dry by midnight.

Sheppard

&&

.SHORT TERM...
Issued 300 AM CDT Sun May 26 2024

Today through Monday night:

Showers and weak storms will gradually push in by around
daybreak this morning as the surface low and corresponding upper
shortwave lifts northeast into the region. This system looks
likely to make for a fairly wet morning and early afternoon with
any individual area looking at a 3-4 hour period of mostly
moderate rainfall (far west/northwest CWA will see rain last
much of the day). Largely, chances for storms seems fairly
limited but with some weak instability, especially along and
south of I-94 some rumbles of thunder cannot be ruled out.

Now in the far southeast the situation is a bit different as
rain should hold off until at least noon which could increase
severe risk. However, models continue to keep the warm front
south of the region with limited instability overall. This
will limit the potential for severe storms as anything would
have to be elevated and even then instability will be very
limited. However we cannot rule out the very slight potential
for some stronger wind and small hail.

As the initial swath of rain swings through the surface low
will begin moving overhead the region. We should (70%) see the
dry slot impact the region for a few hours keeping things dry
for a few hours in the mid to late afternoon. However later in
the afternoon and into the early evening some showers and maybe
even a few storms will be expected in association with the
surface low. Given cooler conditions aloft we should expect some
better lapse rates which could (10%) give some secondary risk
for hailers during this period. Models suggest largely just
showers but conditions support at least weak potential.

The deepening surface low will gradually push northwest into
the northern Great Lakes region and into Ontario. Monday may
feature some additional precip chances (35-45%) due to some
additional shortwave activity in the region along with some
moisture. Best chances for precip are focused further west but
there will be some storms chances for much of the CWA. Storms
will be at least partially diurnally driven as instability
increase somewhat into the afternoon across the area. Stronger
storms not expected at this time due to lack of shear.

Southeast winds and building waves are likely to create Moderate
Swim Risk conditions on today for Lake Michigan beaches. A High
Swim Risk cannot be ruled out but trends have pushed nearshore
waves down this afternoon.

Kuroski

&&

.LONG TERM...
Issued 300 AM CDT Sun May 26 2024

Tuesday through Saturday:

Tuesday will also feature continued chances (40-50%) for
showers and storms, though weak, due largely to the upper trough
digging through the region. While there remains some
uncertainty with this upper trough and its progression from
central Canada into the western Great Lakes region the trend
points toward better chances for a day similar to Monday with
diurnal convective influence but with less certainty in regards
to location of where we should see shower/storms and how
widespread it will be. Recent trends do suggest best chances
will be further north.

By midweek it appears for at least a short period we will
finally return to drier conditions with higher pressure sliding
in ahead of ridging aloft. Friday looks a bit more uncertain but
most models suggest a drier solution with any precip concerns
holding off until at least Saturday. The weekend looks as though
it will feature a system coming through but models disagree on
timing. However that will be something to watch as the week
progresses.

Kuroski

&&

.AVIATION...
Issued 1025 AM CDT Sun May 26 2024

Widespread rainshowers continue to gradually lower cloud
ceilings, with MVFR / Fuel-Alt levels expected this afternoon
(beginning with western areas closer to the core of the low
pressure), followed by IFR tonight. As the core of the low
passes, expect southeast winds to veer west and then northwest
this evening. Rainshowers should decrease to scattered coverage
this afternoon, but would then be more likely to possess
thunder (50% chance). Airports south of KMSN and KMKE would be
the most likely to experience any stronger storms, with a very
low chance (risk level 1 out of 5) for severe thunderstorms with
wind gusts and hail. Showers exit from southwest to northeast
late this evening, with KSBM being the only airport with much of
a chance for rain (50%) after midnight. Cloud ceilings
gradually lift on Monday.

Sheppard

&&

.MARINE...
Issued 300 AM CDT Sun May 26 2024

High pressure over Lower Michigan will move east into New
England today, while low pressure lifts from Kansas into
western Illinois by this afternoon, and then to southern Lake
Michigan by late tonight. This will result in increasing
southeast to east winds across the lake for today, with showers
and thunderstorms likely at times today, largely for the
southern portion of the lake.

That low will then progress northeastward to Lake Huron by Monday
afternoon, with winds quickly turning northwesterly as the low
departs. West to northwest flow will persist into mid week, with
winds gradually weakening over time as high pressure eventually
builds into the region.

Slight chance for small craft conditions to be met this
afternoon and again Monday afternoon.

Kuroski

&&

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

$$

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