NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 190144
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
844 PM CDT Mon May 18 2026

.KEY MESSAGES...

- Another round of showers and storms late tonight into Tuesday
  with a small potential for strong to severe storms.

- Cool and drier weather then returns for midweek.

- Rain chances return Friday (45-55%), followed by a gradual
  warming trend Saturday into early next week.

&&

.UPDATE...
Issued 844 PM CDT Mon May 18 2026

The strong to severe MCS over south central IA will once again
encounter much greater MLCIN and high LFCs as it continues newd
toward the MS River. Thus a dissipating MCS will likely move
into sw WI after midnight. However, still expect fairly
widespread showers and sct storms to move across all of srn WI
during the early morning hours as a sswly low level jet of 40
kts increases warm, moist advection and boosts elevated CAPE to
1000-2000 J/KG. Wind gusts will be the main concern with any
storms.

A wave of low pressure along the stationary front over IA will
track newd to west central WI by 06Z then near Lake Superior by
12Z Tue. The low will then track ewd into Quebec during the day
with its trailing cold front moving across srn WI Tue AM into
the early afternoon. Moist low levels and marginal instability
could result in a broken line of showers and isold storms along
the front but no severe wx is anticipated.


Gehring

&&

.SHORT TERM...
Issued 200 PM CDT Mon May 18 2026

Late this afternoon through Tuesday night:

Quiet weather largely expected the rest of the afternoon into
the evening with remnant convection moving off to the east with
quite a bit of clearing ongoing right now ahead of developing
storms to the southwest this afternoon and evening. This is what
we will be monitoring tonight as it pushes into the CWA. Based
on the development of this convection will in part determine how
things play out tonight. Several models favor development and
progression into a QLCS with a eastward progression. Most
models have this potentially becoming elevated in addition to
limited instability. As this pushes east toward southeast WI
CAMs largely have this falling apart with very limited
instability and very likely an elevated system at that point,
which would reduce severe risk to essentially zero. However, it
is worth mentioning that clearing this afternoon has definitely
increased our severe risk as we will likely be able to hang on
to a bit more instability and may avoid storms immediately
becoming elevated as they reach the CWA. The best severe risk
for tonight will be in southwest WI, likely southwest of
Madison, with decreasing risk further east. We will need to
monitor storms to the southwest tonight as the development and
progression will play a role in determining the potential for
severe storms later tonight.

The remnant storms and precip will push out by mid morning with
our attention turning to the cold front that will closely
following the exiting precip. There is a mild concern for
developing storms along the front but with departing storms in
the morning it does not appear there will any recovery time
ahead of the front with models suggesting very limited
instability and frankly not a great shear environment either.
This suggests that event should week storms develop they would
not likely be of concern. The front should push in by the late
morning and push through all of southern WI by early to mid
afternoon. The best chance for weak storm development with the
front is likely in southeast WI where the best chance for
recovery would be. Otherwise, expect quiet conditions into the
late afternoon and overnight as winds turn northwest behind the
front with higher pressure gradually pushing behind it.

Kuroski

&&

.LONG TERM...
Issued 200 PM CDT Mon May 18 2026

Wednesday through Monday:

Cool and dry weather expected Wednesday and Thursday, with strong
high pressure passing overhead and northeast to east winds off of
Lake Michigan (around 10 to 15 MPH at times). Much of eastern WI
should see highs in the 50s, with low to mid 60s further west.
Some much needed calm and quiet weather.

Our next noteworthy chance for precipitation arrives Friday, with
roughly half of the available model guidance resolving a low
pressure system tracking northeastward from the Great Plains and
approaching our region. The favored track of this system would
stall it either to our south or our west, with the continued
onshore flow from Lake Michigan helping to reduce instability and
prevent substantial moisture return over southern WI. Hence, we
only forecast slight chances for thunderstorms Friday, with rain
chances increasing from 15-55% in a southwest to northeast manner
as the day goes by. As with any low pressure system this time of
year, we will have to keep an eye on it's track and evolution,
but ensemble consensus strongly suggests insufficient moisture
return / instability for much in the way of thunder.

Predictability drops substantially for Saturday and onwards, but
the general consensus is a warming trend that continues into early
next week.

Sheppard

&&

.AVIATION...
Issued 844 PM CDT Mon May 18 2026

VFR conditions this evening then numerous showers and scattered
storms during the early morning hours. Areas of MVFR Cigs and
Vsbys may linger after the rain. More widespread MVFR Cigs will
then overspread srn WI just after sunrise and ahead of the
approaching cold front. Localized Cigs below 1 kft are possible
over south central WI. The Cigs will dissipate after the cold
frontal passage from mid to late afternoon. Gusty swly winds to
30 kts are expected on Tue especially over ern WI.


Gehring

&&

.MARINE...
Issued 844 PM CDT Mon May 18 2026

A Dense Fog Advisory is in effect tonight through Tuesday morning
for the north half of the lake as relatively mild and humid air
flows over the cold lake waters. Otherwise modest to breezy
southerly winds will develop tonight and last into early Tuesday
afternoon, then followed by the passage of a cold front. Winds
will shift to northwesterly with the cold frontal passage and
remain a bit breezy. Scattered thunderstorms can be expected over
the central and southern portion of the lake late tonight into
Tuesday. High pressure around 30.4 inches will then move into
the northern Great Lakes for Wednesday afternoon into Thursday.
Light and variable winds taking hold from late Wednesday into
Thursday. A Small Craft Advisory is in effect from Sheboygan to
Winthrop Harbor from early morning Tuesday into the afternoon
for breezy southwest winds.

Gehring

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646...4 AM
     Tuesday to 4 PM Tuesday.

     Dense Fog Advisory...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
     LMZ567-LMZ868 until noon Tuesday.

&&

$$

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