FXUS63 KGRB 190551
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1251 AM CDT Tue May 19 2026

Updated aviation portion for 06Z TAF 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 06Z TAF Issuance
Issued at 1251 AM CDT Tue May 19 2026

Ongoing line of rain and thunderstorms is moving east across
central and into northeast WI as of 0530Z. The main line has
exited KAUW, KCWA, and KRHI, but a small thunder threat remains 
for the next couple hours from additional development to the south.

Main hazard along and east of the main line over the next 3 to 4 
hours will be strong wind gusts to 40 knots and heavy rain. There 
remains a small potential for isolated severe wind gusts to 50 
knots, but expect this potential to diminish as the storms move 
east. 

Widely scattered showers remain throughout Tuesday morning, with
conditions area-wide drying out after ~18Z. Most location are
still VFR, but expect cigs to drop to IFR/MVFR overnight, with 
improvements to MVFR/VFR this afternoon. Additionally, fog off
Lake Michigan will drop vsby at KMTW at times through Tuesday
morning. 

South winds veer southwest overnight, and then veer to the west-
northwest Tuesday behind the cold front, along with wind gusts to
25 kts.

&&

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

&&

$$

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