NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 181844
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
144 PM CDT Mon May 18 2026

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Isolated severe storms possible through tonight. Greatest
  coverage of storms northwest part of the area late this evening
  and overnight.

- Drier and cooler mid to late week. Frost or freeze headlines may
  be needed Tuesday night and Wednesday night.

- Warmer by next weekend with return of rain chances.

&&

.DISCUSSION...
Issued at 142 PM CDT Mon May 18 2026

Main concern is chance of severe storms through tonight ahead of
an approaching cold front. Modified warm front is working through
the area from the south. It is running into affects from earlier
storms to south and southeast. Subsidence to west of storms over
Michigan is resulting in minimal re-development of showers and
storms thus far. Decent cu field is blossoming over western WI
into central WI, but capping is noted on forecast soundings in
these areas rest of the day. Lowered pops to slight chance all
areas through 5p. An warm and certainly more humid day by recent
standards.

Primary convective development this afternoon into early evening
will be well to the south over the central Plains. As the warm
front lifts north, it could be enough to overcome the capping for
a few storms to develop, especially northern WI. Isolated strong
storm is possible with MUCAPE up to 1000J/kg and effective shear
of 30-40 kts. Severe threat will be higher if a storm could
become truly surfaced based and occur near the front. Wave to
north of this convection over the plains along with approaching
sfc low looks to bring best chance of a line of storms late this
evening into the overnight hours for central and north-central WI.
Main hazard with these storms will be gusty winds and heavy rain.
Isolated damaging wind gust could occur if line remains more
organized as it moves into the area. Overall the chance for severe
weather this afternoon through tonight has trended downward as SPC
has trimmed the Slight Risk out of all our forecast area.

Leftovers of this overnight line of storms shift by late tonight.
A few showers or storms may linger through the morning over eastern
WI, just ahead of cold front. The front sweeps through by early
afternoon, shifting southwest winds to northwest. Winds will be
gusty up to 30 mph. Highs could touch 70 over eastern WI, but will
be in the 60s for most, with even some 50s over north-central WI.

Beyond Tuesday, rest of the week looks generally dry. Canadian
high shifts across late Tuesday through Wednesday night. Frost or
freeze headlines may be needed Tuesday night and Wednesday night,
especially northern WI. Greatest risk is Wednesday night with
high overhead and PWATs less than 0.5 inch. Min RH will be low Wed
through Fri afternoon's. Return flow kicks in late this week into
next weekend with highs steadily returning to at or above normal.
Chances for rain and perhaps some thunder increase by next weekend.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1256 PM CDT Mon May 18 2026

Low pressure and a modified warm front lift across WI through
tonight. Cold front sweeps through on Tuesday morning. Subsidence
in wake of cluster of storms over Lake Michigan and lower Michigan
will restrict pop-up showers and storms this afternoon. As the warm
front lifts through, could be isolated showers and storms late this
afternoon into this evening. Another line of showers and storms will
move into central and north-central WI late this evening and overnight.
Not clear whether this line makes it into eastern WI. A few lingering
showers and storms on Tuesday morning, then it dries out with gusty
northwest winds developing behind the cold front.

Cigs MVFR to VFR today, lowering to IFR to MVFR late tonight into early
Tuesday. Cigs improve to VFR in all areas on Tuesday afternoon.

Southerly winds gust to 15-20 kt into this evening, with winds shifting
southwest into the overnight. Winds shift to northwest Tuesday morning,
with gusts to 25 kt.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION.....JLA
AVIATION.......JLA