NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 131840
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
140 PM CDT Thu Aug 13 2026

.KEY MESSAGES...

- Main area of rain moves through this afternoon, chances into
  this evening. Low probabilities (<10%) of lightning occuring.

- Next round of potential storms is on Friday night into
  Saturday morning. Strong to severe storms are not expected.

- Drier & more comfortable into early next week, with storm
  chances returning by mid-week.

&&

.SHORT TERM...
Issued 140 PM CDT Thu Aug 13 2026

Tonight and Friday:

Rain associated with the northern portion of a large MCS moving
through southern Wisconsin will end from west to east this
afternoon into the early evening hours. There's some brief
potential for long flash lightning strikes for a period as an
area of 30dBZ+ reflectivity comes through at 0C. Once that moves
through, the lightning and thunderstorm potential should end.
Past few runs of the HRRR/RRFS have been holding onto some
shower development but any decent instability will be shunted
well to the south due to this complex moving through.

Going late tonight into Friday, some weak ridging pushes in on
the back side of the MCS and should keep things dry for much of
this period. Am expecting surface dew points to drop a bit in
the wake of the MCS as well, so with upper level cloud cover and
the lower Tds, am not expecting widespread dense fog to form
again tonight.

Halbach

&&

.LONG TERM...
Issued 140 PM CDT Thu Aug 13 2026

Friday night through Thursday:

The next best chances for storms in a very uncertain pattern
comes on Friday night into Saturday morning. 13.12z guidance
shows a 500mb trough ejecting northeastward out of Colorado and
propagating northeast to eastward into Saturday morning with the
vort max going right through southern WI. In the lower levels, a
surface low currently over Kansas is expected to follow a
similar track into southern Wisconsin with a strong push of
925-850mb moisture transport out ahead of it. Guidance suggests
rain moving into southwest Wisconsin after 7pm Friday night with
the most widespread rain coming in after midnight through
daybreak Saturday. Forecast soundings show fairly warm air aloft
with minimal instability to work on. Therefore, am thinking the
severe potential is fairly low on this round of storms and will
moreso be another beneficial rainfall. Can't rule out some
lightning for the late evening Friday and Saturday morning for
any events and farmers markets occuring over this timeframe.

Sunday is rather questionable at the moment for whether there
will be any rain as the 13.12z NAM/GFS both push the boundary
out of southern Wisconsin in the wake of the Saturday low while
the ECMWF is slower to bring it through. Have some small chance
POPs in there to cover the ECMWF solution.

Beyond that, the early portion of next week features a broad
ridge of high pressure before return southerly flow kicks back
in. Another trough looks to swing down from Canada around mid-
week which could lead to the next chances for rain/storms.


Halbach

&&

.AVIATION...
Issued 140 PM CDT Thu Aug 13 2026

MVFR conditions are expected to improve into this evening as the
rain ends from west to east across southern Wisconsin. Am not
expecting fog to form tonight due to the expansive cloud cover
and lower dew points that are expected to set up tonight. The
next round of rain/storms appears to be Friday night into
Saturday morning which could bring conditions back down to MVFR.

Halbach

&&

.MARINE...
Issued 140 PM CDT Thu Aug 13 2026

The main period of windy conditions appears to be on Saturday as
a low pressure system moves in toward the southern end of Lake
Michigan. The 13.12z GFS is the strongest with these winds while
the 13.12z ECMWF shows weaker winds. After that system moves
through, winds should become weaker again until another front
drops down into the region toward the middle of next week.

Halbach

&&

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

$$

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