704
FXUS63 KGRB 170837
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
337 AM CDT Sat May 17 2025

Forecast discussion for routine morning forecast issuance

.KEY MESSAGES...

- Breezy today, though not near as windy as yesterday. Cloudy and
  cool with some light showers or sprinkles through the day.

- Cold Sunday night with a 70-90 percent chance of temperatures at
  or below freezing over northern Wisconsin.

- Cool trend continues into much of next week. Chance of rain late
  Monday night through Tuesday night, otherwise dry.

&&

.DISCUSSION...
Issued at 334 AM CDT Sat May 17 2025

A cool weekend is in store as the western Great Lakes will remain
to the west of slow moving H85-H5 low, some 2-4SD below normal.
Greatest chances for rain will be today, but coverage will be
spotty (20-40%) and rain amounts will be well under 0.10 inch.
Sfc low has unraveled compared to what it was 24 hr ago (down to
around 980mb over the Dakotas around daybreak Friday). The low is
now around 992mb over Lake Superior this morning but changes little
in strength through the afternoon. This will keep a tight
pressure gradient in place, leading to breezy northwest winds up
to 30 mph late this morning into the afternoon, so not near as
strong compared to what occurred across the area yesterday.
Temperatures will be cooler than average and much cooler than what
we have seen recently. Highs today will remain in the 50s central
and north-central, to 60-63F from the Fox Valley and lakeshore
into far northeast Wisconsin.

Cyclonic NW-N flow keeps plenty of clouds around tonight with
some sprinkles at times, especially north. Lows may drop to the
mid 30s north but with clouds and wind, no real risk of frost.
Readings will be in 40s elsewhere. Due N winds on Sunday off Lake
Superior will keep clouds and a few sprinkles across the north.
Clouds will slowly scatter out elsewhere. More of a gradient in
highs on Sunday with only mid 40s north, but as warm as lower 60s
parts of central WI along and south of highway 10 where there will
be more breaks of sun.

Only real impactful weather is Sunday night. Once clouds clear out
as high tries to ridge into northern WI, stage will be set for a
chilly night. NBM probabilities remain very high (over 70%) that
parts of northern WI will see sub-freezing temps. Trouble is that
soundings point to winds to not completely decouple. This could be
situation of freeze or nothing as radiational cooling potential
seems lower for a lot of frost. Will introduce the potential for
frost or freeze in this mornings HWO.

Rest of the forecast features cooler temps, with highs likely
remaining below normal through at least Thursday. EC EFI highlights
indicates that EC Ensemble is shifting in a negative way from the
reforecast climatology for highs much of the week. Coolest days
will be Monday through Wednesday. Jet energy emerging out of western
CONUS trough will result in several rounds of severe weather for
the central and southern Plains, but thunder risk will be minimal
up our way. Late Monday night through Tuesday night could see some
rain make it into at least the southern forecast area, but north
could stay dry. Seems that the canadian sourced high over Hudson
Bay will really try to put brakes on northern progression of the
rain. Models and ensembles have signaled this for many days now.
Outside that chance of rain, dry weather should prevail through
rest of the workweek.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1034 PM CDT Fri May 16 2025

CIGs will lower behind a cold front overnight to a mix of MVFR/IFR
along with some post-frontal showers. These conditions will last
through Saturday with the showers winding down Saturday afternoon
into the evening as the upper level low pulls away from the area.
Surface winds will also increase again and peak late Saturday
morning through the afternoon with gusts up to 30 kts.

&&

.MARINE...
Issued at 334 AM CDT Sat May 17 2025

West winds shift to the northwest this afternoon, with gusts over
20 kts at times into this evening. Higher gusts now expected to
linger well into the evening, so extended the Small Craft Advisory
for all areas. Highest waves will be early this morning before winds
shift offshore later this morning through tonight.

&&

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

&&

$$

DISCUSSION.....JLA
AVIATION.......Kurimski
MARINE.........JLA