NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 011130
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
630 AM CDT Fri May 1 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Scattered showers return this afternoon, with a flurry or two
  possible across the north. More widespread rain/thunder then
  arrive Sunday and Monday.

- High confidence in another round of frost/freeze headlines late
  tonight into early Saturday morning as lows fall into the low
  20s to low 30s.

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

- Below normal temperatures expected through most of the forecast
  period, with the exception of Sunday and Monday.

&&

.DISCUSSION...
Issued at 154 AM CDT Fri May 1 2026

Still struggling with some low clouds that are slow to exit across
eastern Wisconsin early this morning, which have generally kept
areas along/south of Hwy 29 in the mid to upper 30s. However,
frost/freeze headlines remain on track as temperatures to the
north have already fallen into the upper 20s to low 30s where
clearing was observed. Radar continues to show some weak returns
near GRB, though obs show no evidence of any showers making it to
the surface.

Rain/storm chances... Par for the course, scattered showers will
return this afternoon as closed upper low drops one more
shortwave down over the Great Lakes before lifting into northern
Quebec. Lack of instability will keep thunder chances little to
none, with QPF likewise being held down to a tenth of an inch or
less. A flurry or two cannot be ruled out as 850 temperatures
reach -4 to -8C.

Brief dry spell looks likely on Saturday as weak high pressure
builds in from the north and synoptic flow flattens out over the
upper Mississippi Valley. Next chances for more widespread precip
then arrive Sunday afternoon in conjunction with cold FROPA. QPF
should be rather limited (less than 0.25"), though narrow corridor
of 200 to 400 J/kg MUCAPE along the front would support a rumble
or two of thunder. However, better thunder chances come Monday
afternoon in tandem with stronger synoptic forcing from a potent
shortwave as well as a plume of steeper mid-level lapse rates.
Probabilistic guidance only shows a broad 15 to 25% chance for
receiving half an inch of rain during this time, though suspect
that locally higher amounts will be possible with convectively-
enhanced precip rates. Severe potential appears rather limited at
this time. Unsettled/showery pattern then persists for much of
next week as several shortwaves pivot around a closed upper low
that sits and spins over the Hudson Bay, similar to the regime we
are currently in.

Temperatures... Well advertised below normal temperatures to
continue through the weekend due to steady stream of cold Canadian
air into the upper Midwest. As such, highs will read mainly in
the 40s and 50s through Saturday afternoon. Some moderation to
near normal is then possible Sunday and Monday as weak WAA and
windows for clearing result in highs warming into the mid 60s and
even low 70s across portions of central Wisconsin to the Fox
Valley. However, the warmth will not be long-lived as post-frontal
temperatures fall back into the 40s and 50s mid-week. CPC
outlooks suggest that this cooler pattern will persist through at
least mid-May.

Frost/freeze headlines... HREF retains strong signal (50 to 80%
chance) for lows dipping below 28F late tonight into Saturday
morning. Current thinking is that this would be more of a slam
dunk widespread frost/freeze setup given mostly clear skies and
light winds, which would necessitate additional headlines on the
day shift. Chances for below freezing lows then sharply decrease
beyond tonight as we get into weak return flow.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 440 AM CDT Fri May 1 2026

Low clouds continue to clear out of east-central Wisconsin early
this morning, leaving VFR conditions in their wake. Scattered
showers then return this afternoon, bringing with them localized
MVFR cigs/vsbys if a shower moves over a terminal. Attempted to
provide timing resolution via PROB30 mentions for -SHRA across the
eastern sites where PoPs are higher. Otherwise, prevailing
conditions should remain VFR through the TAF period. SCT to BKN cu
with bases at around 4 to 5k ft may develop later this morning,
lasting through this evening. Winds will be mainly out of the
north, gusting between 10 and 15 knots this afternoon.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Frost Advisory until 8 AM CDT this morning for WIZ022-031-
037>040-048>050.

Freeze Warning until 8 AM CDT this morning for WIZ030-035-036-
045.
&&

$$

DISCUSSION.....Goodin
AVIATION.......Goodin