431
FXUS63 KGRB 242343
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
643 PM CDT Sat May 24 2025

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Patchy/areas of frost expected across central/northern Wisconsin tonight
  into Sunday morning.

- Isolated to scattered showers expected through early this
  evening. Next chance for widespread rain arrives late Tuesday
  into Wednesday.

- Temperatures slightly below to to near above normal.

&&

.DISCUSSION...
Issued at 209 PM CDT Sat May 24 2025

Precip Chances & Cloud Trends:

A solid deck of broken to overcast cumulus clouds have formed
across the region late this afternoon given the cold air aloft.
Isolated to scattered showers/sprinkles will continue into early
this evening until the region loses daytime heating as a
shortwave takes advantage of 100-200 J/kg of instability. Cloud
bases will be quite high, with dry air near the surface to
overcome, which could limit just how much rain makes it to the
ground. Soundings showing an inverted-V through early this
evening, but not much wind to mix into to with only ~20 kts at
10,000 ft. But with light winds at the surface, any shower could
bring down higher winds with some 20+ mph gusts possible. Similar
set up on Sunday with just a little less instability, with eastern
WI looking more favorable for any light precip activity, closer
to the upper trough and cooler air aloft. Will keep the chance of
sprinkles to eastern WI to at least get a little precip in the
forecast, but not expecting anything too widespread.

Monday is looking dry as the upper low shifts east of the region
and weak high pressure moves across the Great Lakes. The trend for
the middle of the week continues to look to be unsettled, with
chances for a more widespread rain arriving late Tuesday into
Wednesday as a slow moving low pressure tracks into the region.
Overall, probabilities of measurable precip is trending upward,
now 50-80%, with greater than 0.10" approaching 50%. Would think
these will continue to increase as models converge on a track
across the Great Lakes.

Temps & Frost/Fog Potential:

Another chilly/cold night on tap for tonight as a cool airmass
remains in place. Lows mainly in the 30s are expected in central
and northern WI, where additional patchy/areas of frost are
expected, as winds remain light. Another Frost Advisory will
likely be needed over north central WI. Lows in the upper 30s to
mid 40s are expected elsewhere. Lows Sunday night will be a little
warmer, with only a few spots in far north central WI expected to
drop into the upper 30s.

In addition to the frost, where/when skies stay clear at night,
some patchy ground fog could develop during the early morning
hours through the weekend. The best chance appears late tonight
into early Sunday morning where probabilities of dropping below 1
mile are 10-15% west and north of the Fox Valley. Probabilities
drop to below 10% Sunday night into Monday when less fog is
anticipated.

Temps will make a run at near normal readings early next week,
but with the upper low (and associated clouds/precip) likely to
stick around during the mid-week period, temps should drop back a
few degrees. A return to above normal temps is more likely as we
start the new month.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 643 PM CDT Sat May 24 2025

BKN-OVC VFR cumulus prevail early this evening with some breaks
in the clouds at times to a SCT deck. Scattered sprinkles or
light showers may occur next few hours, but should have little to
no impacts on aviation. Additional patchy ground fog will be
possible again late tonight into early Sunday (09z-12z), with the
lowest conditions expected across north-central Wisconsin where
VSBYs could fall to IFR/LIFR at RHI. Any fog will mix out after
12Z. Winds through the period will be light, generally less than
10 kts. A brief higher wind gust (15+ kts) is possible in or around
any shower early this evening.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from 1 AM to 8 AM CDT Sunday for WIZ005-010>012-
018-019.
&&

$$

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