790
FXUS63 KGRB 301030
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
530 AM CDT Thu Apr 30 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Another round of rain showers today, mixed with snow north.
  Small chance of showers on Friday. Dry Saturday, then chances
  for more showers Sunday into next week.

- Frost Advisory for central WI to the Fox Valley early this
  morning. Additional frost and freeze headlines expected over
  central and east central WI tonight. Freeze looking likely for
  much of the area Friday night.

- 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 154 AM CDT Thu Apr 30 2026

Near term through tonight...Showers have exited early this
morning. Patches of stratocu clouds will lead to variable temps
early this morning, but with temps in the mid to upper 30s, some
frost is expected where skies can clear. Attention is on shortwave
north of Lake Superior in general troughing. Expect this wave to
dip over western Great Lakes by this afternoon, resulting in
another round of showers from mid morning through early evening.
Colder aloft this time around, with H85 temps over northern WI
bottoming out around -5c. Soundings look to support snow more than
rain. A smattering of rain/snow or just snow showers seen in much
of the high-res guidance especially north. Sfc temps, ground
temps appear too warm and snowfall rates too low to lead to any
accumulation on the ground, but snow in the air is likely from
Rhinelander northward.

Once showers end this evening, another chilly night is in store,
but similar to early this morning, based on upstream obs and HREF
guidance, there will be a fair amount of stratocu to modulate
temps. Nevertheless, Frost/Freeze headlines will be needed in some
shape or form again. With current headlines out for early this
morning, will let dayshift issue the new set of headlines.

Precipitation chances beyond today: One last shortwave set to drop
across on Friday. With a nod to persistence and since some models
are showing at least light QPF, opted to add some slight chances
for showers. Ptype looking mainly like rain as colder air aloft
does ease. 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. MUCAPES up to 300-400J/kg with
plume of mid- level lapse rates over 7c/km support slight chance
of thunder. 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: Sfc ridge overhead with less troughing
aloft will promote better chance of clearing and light winds
Friday night. Expect temps widespread temps at or below freezing.
Thus, a widespread freeze is looking likely. Recent LREF runs
point to over 90% chance of seeing temps less than 32, even into
the Fox Valley, with a 50-80% chance of seeing temps less than 28
for portions of central WI. 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 12Z TAF Issuance
Issued at 529 AM CDT Thu Apr 30 2026

Skies are mostly clear to mostly cloudy early this morning, with
BKN VFR clouds over central WI and BKN MVFR clouds in far northeast
WI to Door County. Clouds will thicken through the morning (mainly
VFR) and another round of scattered showers are expected this
afternoon into this evening. Cigs will mainly remain VFR, but dips
to MVFR are possible during any showers. It will be cold enough
for some snow or graupel over northern WI. Included a PROB30 at
RHI as vsby could briefly drop to IFR there this afternoon during
heavier showers, especially if ptype is only snow.

Lingering showers will end by late this evening over eastern WI.
Skies will gradually become partly cloudy (VFR).

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Frost Advisory until 8 AM CDT this morning for WIZ030-031-
035>039-045-048-049.
&&

$$

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

NWS GRB Office Area Forecast Discussion