Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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606
FXUS63 KMKX 120306
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1006 PM CDT Sat May 11 2024

.KEY MESSAGES...

- Warm on Sunday, with scattered showers and thunderstorms.
  Storms may initiate as early as the mid afternoon, but
  coverage should be highest in the evening hours due to an
  approaching cold front. Rain chances continue Monday.

- Additional rain chances middle to end of the week.

&&

.UPDATE...
Issued 1000 PM CDT Sat May 11 2024

Diurnal cumulus clouds have eroded rapidly, leaving skies mostly
clear. GOES is tracking an arc of thin and scattered high
altitude clouds from northwestern WI through central WI, but
these shouldn`t have much of an impact for folks viewing the
northern lights, given the thin and dispersed texture. A gradual
increase in cloud coverage may occur after 2 AM, hence between
now and then is the best window for sky viewing.

For the Sunday mid-afternoon through evening/night thunderstorm
setup, forecast soundings show deep inverted-v signatures, with
20 to 30 kts of deep shear (which may support clusters or line
segments, but not supercells) with high LCL heights. The main
triggering mechanism for convection appears to be the SW to NE
oriented cold front sagging southward into our CWA Sunday
evening, but some CAMs are beginning to hint at prefrontal
initiation in the mid to late afternoon. Hence, the highest
storm coverage and rain chances are in the evening hours (as the
front approaches), with more isolated activity possible in the
afternoon. Instability is only marginally favorable for severe
weather (1000 joules or higher in some models with sfc dewpoints
well over 50 F, less than 1000 joules for models with upper 40s
to low 50s dews as currently forecast), hence few (if any)
storms are expected to reach severe criteria. If storms
over-perform, wind gusts would be the primary threat. Storms
that initiate in advance of the front (afternoon) may have
enough CAPE for a hail threat as well.

Sheppard

&&

.SHORT TERM...
Issued 242 PM CDT Sat May 11 2024

Rest of this Afternoon through Sunday night:

Scattered showers will continue to impact the lakeshore areas
mainly north of Milwaukee through this afternoon, within an area
of deeper moisture and cyclonic flow. Elsewhere, scattered to
broken fair weather cu will persist through late afternoon,
before dissipating this evening. Winds will remain breezy from
the northwest.

High pressure builds into the region this evening, which should
result in a period of mostly clear skies, along with light
winds. Temperatures are expected to fall into the mid to upper
40s, before leveling off and then slowly rising toward sunrise
as warm advection increases across the region, which will also
result in an increase in mid and high level clouds. An area of
showers and a few thunderstorms associated with the warm
advection will develop over northern Wisconsin, but should
remain north of the forecast area through Sunday morning.

Warm temperatures are expected on Sunday, with gusty southwest
winds helping to boost highs into the upper 70s and low 80s. A
weak frontal boundary will begin to sink southward into the
region during the afternoon hours, setting off scattered showers
and thunderstorms. A number of places may remain dry, and those
that do see a shower/storm shouldn`t expect the rain to last too
long. Rain chances will persist into the late evening as the
weak boundary pushes south, before coverage wanes late Sunday
night.

Boxell

&&

.LONG TERM...
Issued 242 PM CDT Sat May 11 2024

Monday through Saturday:

The aforementioned frontal boundary will settle into northern
Illinois by early Monday. Lift will increase across the boundary
Monday and Monday evening ahead of a shortwave moving across the
central Plains, aided by the right entrance region of a
strengthening upper jet over the UP and eastern Ontario. This
should result in several rounds of showers and thunderstorms
across southern Wisconsin, with the greatest concentration along
and south of I-94. Highs will be a touch cooler, topping out in
the low to mid 70s.

High pressure will nose in from the north on Tuesday and
Wednesday, with cooler north to northeast flow and dry weather
expected.

Another series of shortwaves look to affect the region Thursday
and/or Friday, with increasing rain chances.

Boxell

&&

.AVIATION...
Issued 1000 PM CDT Sat May 11 2024

VFR conditions continue tonight, with mostly clear skies (high
altitude clouds) and winds light and variable. Light south winds
at sunrise veer southwest late Sunday morning, with gusts
upwards of 20 kts in the afternoon. A cold front sagging
southward into the region Sunday evening will lead to gradually
increasing shower and thunderstorm coverage, with cumulonimbus
bases at roughly 5,000 to 10,000 ft. Storms firing in advance of
the front (as early as mid afternoon Sunday) cannot be ruled
out.

Sheppard

&&

.MARINE...
Issued 242 PM CDT Sat May 11 2024

Northwest winds will become light and variable tonight as weak
high pressure moves across the lake. The high will shift east
early Sunday morning while a wave of low pressure and its
associated cold front moves across northern Lake Michigan Sunday
night. This will result in breezy southerly winds on Sunday
shifting to northerly and weakening late Sunday night. The cold
front will move south on Monday bringing light to modest
northerly winds to the entire lake.

High pressure is then expected to move across the Great Lakes
Tuesday and Wednesday. Winds will be from the north during this
time. Gusty north winds may reach Advisory levels on Tuesday.

Boxell

&&

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

$$

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