NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 261844
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
144 PM CDT Fri Jun 26 2026

.KEY MESSAGES...

- Chance for showers and storms for late Sunday
  morning/afternoon.

- Prolonged period of hot and humid conditions expected for the
  start of next week through end of the week with potential for
  heat indices around to above 100F.

- Additional shower/storm chances accompanying the heatwave
  Tuesday through end of week

&&

.SHORT TERM...
Issued 138 PM CDT Fri Jun 26 2026

Tonight through Saturday night:

Zonal upper-level flow and a weak low pressure tracking across
central IL bringing the cloudy conditions this afternoon will
continue to shift east this evening. Looking at lingering cloud
cover to insulate the area and keep temps overnight a degree or
two warmer than previous forecast with lows dipping low to mid
50s.

Then looking a upper-level ridge begins to build across the
region for Saturday. Will begin to see warmer temps along with
higher dewpoints (upper 50s to around 60F) advect into southern
WI. However, easterly onshore flow on the backside of the
departing weak low and north of a frontal boundary will
ultimately prevent the warmer temps. Only looking at daytime
highs in the mid to upper 70s for areas along and east of the
Kettle Moraine while upper 70s to low 80s for areas west/further
inland for Saturday. While expect less cloud cover for
Saturday, cannot rule out a few more patches of mid to high
level clouds fill in as suggested by 12z HREF, which could knock
daytime temps down a few degrees. Otherwise, overnight lows are
trending warmer than the previous night with upper 50s to low
60s.

Wagner

&&

.LONG TERM...
Issued 138 PM CDT Fri Jun 26 2026

Sunday through Friday:

The upper-level ridge continues to build across Upper
Mississippi River Valley and bringing the warmer and muggier
conditions to southern WI. However, models continue to hint at a
mid-level vorticity max overrunning the top of the building
upper-level ridge and trekking across the region later Sunday
morning. The tail end of the 12z CAMs are hinting at MCV type
structure and this disturbance paired with the low-level WAA
and increasing moisture looks to be enough for a scattered
showers and storms chances (20-40%) across southern WI. Given
the general timing of late morning/early afternoon of this
feature, the NAM along with GFS and ECMWF are hinting at some
increased deep-layer shear and building instability with MUCAPE
creeping toward 750-1200 J/kg with this system. While, difficult
to pinpoint if these features will line up pairing with the
influence from the MCV, but it is not out of the realm of
possibility to see a bit more widespread coverage in activity
than latest models suggest and even a potential for a few
stronger storms cannot be ruled out, especially a slightly later
timing. Will monitor as CAMs come more into range.

Otherwise, the main story of the extended will be the building
heat risk as the upper-level blocking high sets up over
southeastern CONUS. Mid and long range models/ensembles continue
to trend toward the higher heat and humidity building into the
area more Monday and continue through much of next week. At this
time, Monday is trending toward seeing triple digit heat
indices, especially for western portion of the CWA. Then the
ridge axis continue to amplify Tuesday through Thursday, with
more widespread triple digit heat indices. Given the
consistency, prolonged nature of this pattern along with this
being the first heat wave of the summer, heat headlines are
looking increasingly more likely for next week as this pattern
becomes dangerous for vulnerable populations with health issues
and/or lack of cooling/hydration.

Lastly accompanying this heat and humid pattern for next, will
be daily chances for showers and thunderstorms as upper-level
disturbance may overrun the ridge. If any showers/storms
develop could end up disrupting the temp forecast and could
lower heat indices with lingering clouds and rain cooled air.

Wagner

&&

.AVIATION...
Issued 138 PM CDT Fri Jun 26 2026

Mid to high clouds will gradually clear out this evening and
VFR conditions will prevail through the TAF period. Looking at
lighter easterly winds tonight into Saturday morning. Easterly
flow will continue through the day Saturday and gradually pick
up a bit toward the late morning/early afternoon hours.

Wagner

&&

.MARINE...
Issued 138 PM CDT Fri Jun 26 2026

High pressure over the the Great Lakes will keep winds lighter
tonight into Saturday, but gradually pick up as the high
pressure slides east. Will then see winds pick up for the later
half of the weekend as low pressure deepens over the Plains and
more southerly winds pick up for the start of next week. Could
see stronger gusts up 30 knots at times as the heat waves
persists across the region. With these gusty winds, small craft
conditions will be possible at times through next week.

Wagner

&&

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

$$

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