185
FXUS63 KGRB 302339
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
639 PM CDT Thu Apr 30 2026

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Additional spotty rain showers through the evening and
  again Friday, with snow mixing in across the northern tier.
  Higher confidence in additional rounds of light rain Sunday
  and into next week.

- Frost/freeze headlines are in effect again tonight with
  temperatures falling into the 30s and even below freezing
  across central WI and the Fox Valley.

- Minor flooding lingers on the Wolf River and Winnebago system.
  Water levels will slowly recede given lack of significant
  rainfall.

- Below normal temperatures expected through most of the period.

&&

.DISCUSSION...
Issued at 140 PM CDT Thu Apr 30 2026

Water vapor imagery and RAP analysis reveal another shortwave
dropping into northern WI, touching off another batch of cold rain
showers. Soundings support snow mixing in at times, especially
nearer to the UP border where surface temperatures are only rising
into the upper 30s and lower 40s so far. Elsewhere, temperatures so
far in the mid 40s so far peak in the upper 40s to near 50 under
cloudy skies. Rain and snow showers largely wrap up by midnight,
with little to no snow accumulations and rainfall coming in
generally below a tenth of an inch.

Tonight, 850mb temperatures drop a couple degrees further to around -
6 to -7C, with skies expected to clear at least partially. This
supports an even cooler night tonight. Lows in the upper 20s to
lower 30s are expected for much of central and northern WI, while
the Fox Valley and Door county bottom out in the lower/mid 30s.
Chilly temperatures, clearing skies, and light winds lead to another
widespread frost/freeze tonight. With that, have issued a Freeze
Warning for central WI, and a Frost Advisory for areas eastward late
tonight into early Friday morning.

Friday, temperatures rebound into the mid/upper 40s, with some spots
making a run towards 50F once again. Another shortwave rippling
through our broader troughing will present another opportunity for
scattered, light rain showers during the afternoon and early
evening.

Precipitation chances beyond Friday: Decent signal we sneak in
at least one dry day Saturday with weak ridging aloft and since
the area will be well downstream of stronger shortwave/sfc
trough working across south central Canada and northern Plains.
As that system arrives for Sunday, expect renewed chance for
showers. A plume of mid- level lapse rates over 7c/km could
support some thunder, though confidence is low. Stronger trough
crosses Monday so chances for showers continue. Better thunder
chances may be south and east of the area by that time following
the plume of steeper mid- level lapse rates. Still some
uncertainty on those details though. Unsettled weather to close
out the rest of the forecast as we return to a regime similar to
what we are seeing at present with northwest flow aloft and
shortwaves riding across the area.

Frost/Freeze Headlines: Latest LREF run points to over 90%
chance of seeing temps less than 32 Friday night, even into the
Fox Valley, with a 50-80% chance of seeing temps less than 28
for portions of central WI. This may necessitate additional
frost/freeze headlines. Beyond Friday night, chances of temps
less than 32 decrease markedly as we get back into a return flow
pattern.

Temperatures: Northwest flow of Canadian air keeps temperatures
below normal through Saturday. For reference, normal highs are now
in the upper 50s to around 60. Some moderation in temperatures (to
near normal) should occur Sunday and/or Monday ahead of cold
fronts that move through, but reinforcing shots of Canadian air
will follow, leading to cooler than normal temps much of next
week. Per CPC days 6-10/8-14 day outlooks, appears this cooler
pattern will persist through at least mid May.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 639 PM CDT Thu Apr 30 2026

BKN VFR cigs continued to filter over the region early this evening.
A few isolated showers also continue to move over far north-east WI,
however, minimal impacts to aviation are expected. Tonight cigs will
generally clear out across northern and central WI leaving VFR
conditions at RHI, CWA, and AUW. Lingering clouds across east-
central WI are expected to gradually lower tonight and will likely
produce a period of MVFR cigs at ATW, GRB, and MTW. Friday will be
similar today with another round of isolated to scattered showers
developing during the afternoon. However, VFR conditions will
generally prevail Friday, but brief periods of MVFR vsbys are
possible as any showers pass over a terminal.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from midnight tonight to 8 AM CDT Friday for
WIZ022-031-037>040-048>050.

Freeze Warning from midnight tonight to 8 AM CDT Friday for
WIZ030-035-036-045.
&&

$$

DISCUSSION.....LC
AVIATION.......GK

NWS GRB Office Area Forecast Discussion