119
FXUS63 KGRB 241638
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1138 AM CDT Sat May 24 2025

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

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

- Isolated to scattered showers expected today. Next chance for
  widespread rain arrives late Tuesday into Wednesday.

- Temperatures slightly below to to near above normal.

&&

.DISCUSSION...
Issued at 336 AM CDT Sat May 24 2025

Precip Chances & Cloud Trends:

Dry conditions with only a few clouds over far north/east WI
prevailed across the area to start the day. Look for clouds to
increase through the morning as cold air aloft will and a well
mixed/unstable boundary layer will allow convective clouds to form.
An an upper trough/low sits just to our north and a weak
shortwave drops south into the region, and as 100-200 J/kg of
instability develops, look for isolated to scattered
showers/sprinkles to develop in the afternoon. 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 this afternoon, but not much wind to mix
into to with only ~20 kts at 10,000 ft. But with light winds at
the surface today, 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 add a 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 mid-
week period is trending toward an 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:

Temps early this morning have dropped into the upper 20s to mid
30s across much of central and northern WI with light winds, so
will allow the current Frost Advisory to run its course through
9 AM.

Temps today will be a little warmer than yesterday, with highs in
the low to mid 60s for most spots, with cooler readings near Lake
Michigan. Another chilly/cold night on tap for tonight as the
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.

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 18Z TAF Issuance
Issued at 1138 AM CDT Sat May 24 2025

BKN-OVC VFR cumulus clouds are ubiquitous across the region this
afternoon with some breaks in the clouds at times to a SCT deck.
Similar to the last few days, isolated to scattered sprinkles or
light showers may occur but should have little to no impacts on
aviation. Additional patchy ground fog will be possible again
tonight into early Sunday, with the lowest conditions expected
across north-central Wisconsin where VSBYs could fall to IFR/LIFR.
Any fog will mix out around 12Z Sunday. Winds through the period
will be light, generally less than 10 kts. A brief higher wind
gust is possible in/around any shower.

&&

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

&&

$$

DISCUSSION.....Bersch
AVIATION.......Kurimski