951
FXUS63 KGRB 162326
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
626 PM CDT Fri May 16 2025

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Scattered showers and thunderstorms through mid-evening,
  particularly across eastern Wisconsin. Isolated severe is
  possible. Diminishing precip/storm chances after sunset.

- Somewhat gloomy on Saturday with cool northwest winds, cloudy
  skies, and isolated showers.

- Cool trend continues into much of next week.

&&

.DISCUSSION...
Issued at 352 PM CDT Fri May 16 2025

Main focus is ongoing thunderstorms along with synoptic winds.
Isolated showers developed in central WI early this afternoon and
quickly grew into a broken line of thunderstorms tracking
northeast--mainly across eastern and northeast WI. These were
mainly the result of daytime heating leading to an area of
instability, with MUCAPE of 400-1000 J/kg, particularly in the
east. There is also a small shortwave ahead of the main upper low,
along with some influence from the LFQ of the upper jet aiding in
large scale ascent. Strong winds have been the main threat with
inverted V soundings showing mixing up to as high as 8-9kft, where
synoptic wind are around 50 kts. Surface gusts near 55mph were
reported with the first showers in Portage Co. Spotter reports
since then have been limited, but radar and atmospheric conditions
would suggest gusts to 60mph remain possible within any
thunderstorms, or even strong showers. Additionally, freezing
levels are quite low near 9000 ft, with 50dBZ to only ~22000 ft
needed for 1" hail. Some of the storms have surpassed this, so
hail up to around 1" remains possible within the strongest storms
as well.

The HRRR has been the most reliable with trends today. Will
continue to follow its general output through the evening. This
indicates the ongoing storms continuing to track northeast, with
some additional development downstream which is currently evident
in south-central WI. This would bring another broken line of
showers/storms through the eastern parts of the CWA late this
afternoon--however, some question to how much instability will be
available. Regardless, with strong winds above the surface and low
freezing levels will continue to see an isolated severe threat
through early this evening. After sunset expect the severe and
thunder threat to greatly diminish, with some isolated to
scattered showers overnight. Winds will also subside overnight.

Saturday...Upper low tracks across the state early, with some weak
wrap around energy behind it. This keeps a low chance (10-20%) of
showers in the forecast, but most of the day will be dry. However,
cooler, cloudy, and breezy conditions are expected with northwest
winds gusting to 30-35 mph and in the middle 50s to low 60s.
Thunder chance is very low with virtually no instability.

Cooler trend continues Sunday and into most of next week with
temperatures at or below normal. Dry weather is likely Sunday and
Monday, with chances for precip on Tue/Wed. However, models are
not in agreement on the track of that system, so the precip could
miss WI to the south.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 625 PM CDT Fri May 16 2025

Scattered showers and thunderstorms will wind down this evening as
they push east of Wisconsin. A cold front will track through the
region this evening, which will lower CIGs to a mix of MVFR/IFR
around 06Z through Saturday morning. CIGs are expected to improve
a bit Saturday afternoon to MVFR/VFR across east-central
Wisconsin. Winds will also increase again and peak late Saturday
morning through the afternoon with gusts up to 30 kts.

&&

.MARINE...
Issued at 352 PM CDT Fri May 16 2025

Gusty south winds and scattered thunderstorms will continue
through early this evening. Winds subside a bit overnight, and
then increase from the northwest on Saturday morning. The strong
winds, along with high waves, will continue through early Saturday
evening for both the bay and Lake Michigan nearshore waters. No
changes to the current Small Craft Advisory.

&&

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

&&

$$

DISCUSSION.....KLJ
AVIATION.......Kurimski
MARINE.........KLJ