Pickerel, Wisconsin Weather Forecast Discussion

470
FXUS63 KGRB 180332
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
1032 PM CDT Wed Sep 17 2025
Updated aviation portion for 06Z TAF issuance
.KEY MESSAGES...
- Additional scattered showers and storms are possible at times
  Thursday through Monday. The risk of severe weather is low.
- Temperatures not as warm, but still above normal Thursday.
  Readings return to near normal from Friday into the weekend.
- Conditions hazardous to small craft will be possible on Lake
  Michigan south of Two Rivers on Friday night and Saturday
  morning. There will also be an increased risk of rip currents on
  Lake Michigan beaches along this section of shoreline.
&&
.DISCUSSION...
Issued at 212 PM CDT Wed Sep 17 2025
Short Term...Tonight and Thursday
Latest satellite analysis continues to show a weak cold front
boundary stretching Wisconsin into the Upper Peninsula, roughly
from Phillips in Price County to just south of the city of
Marquette. Surface parameters in the region meanwhile show
building surface based CAPE values to around 1500-2000 J/kg of
CAPE, indicating a favorable unstable conditions. As the front
interacts with this instability, scattered rain and thunderstorm
activity is anticipated in the afternoon, largely focused towards
northern Wisconsin. Indeed, as of this early afternoon a couple of
storms have already developed over the Upper Peninsula of
Michigan. As we get into the evening, a few showers or storms may
ride outflow southwards and expand active weather coverage
southwards, but are still largely expected to stay well north of
Highway 29, including the Fox Valley and Green Bay areas. Shear
remains virtually nonexistent, so any storms will likely be
fairly pulsy in nature and slow moving, making any impacts fairly
localized. Any thunderstorms will have the potential for heavy
rain, small hail, and brief but strong wind gusts up to 40 mph.
As the rain away from the cold front will be largely diurnally
driven, quieter conditions are expected to return rapidly
overnight, although a few showers could continue in the far north
along an area of better moisture convergence. The front will also
bring some drier air in, which should mitigate much of the fog
potential for northern Wisconsin. Areas further south could still
see some patchy fog, namely for central and east-central, but
dense fog is not expected.
Thursday will see warm conditions continue, but cooler air will
bring high temperatures down by around 5 degrees compared to
today, with highs ranging from the middle 70s to the lower 80s.
Scattered shower activity and a rumble of thunder will still be
possible, mainly along the stalled cold front in northern
Wisconsin and an area of weak convergence across central Wisconsin
brought in by a larger low pressure system to our west. Without
more widespread support however, coverage of active weather will
be somewhat limited.
Long Term...Thursday Night Through Wednesday
The synoptic blocking over CONUS will break down over the first
few days of the extended, allowing the upper trough to progress
across the region through the weekend. Ahead of this, isolated
shower activity is likely to continue across portions of central
and northern Wisconsin Friday and Saturday before the more
widespread forcing arrives. A round of more widespread rain and
storms is then likely for Saturday night into Sunday. Return flow
accompanying the trough will bring in another surge of warm air,
holding high temperatures in the 70s into early next week.
Active weather will accompany the warmer air, with storms and rain
likely again Sunday evening and early next week when a larger low
pressure system is expected to develop over the Central Plains.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1028 PM CDT Wed Sep 17 2025
Lingering showers and isolated storms over far northern WI will
slowly fade into the early overnight. May see another round of
scattered showers over the north late tonight toward daybreak,
which would linger through much of the morning. Have added a
PROB30 group at RHI to cover the potential. Based on expected low
temperatures and crossover temps, kept a mention of patchy ground
fog at most of the TAF sites. RHI and GRB figure to see greatest
risk of saturation (IFR vsby), but there may be just enough wind
to keep fog from dropping to anything less than MVFR.
Rest of Thursday will feature more clouds than has occurred
recently, MVFR to VFR in the morning, rising to VFR all areas in
the afternoon. E-NE winds up to 10 kts will prevail at all TAF
sites through the morning, then increase with gusts over 15 kts in
the afternoon and evening. Another round of isolated to scattered
showers and storms may make it into north-central and central WI
late Thursday afternoon, but confidence is too low to include any
mention at this point.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION.....Uhlmann
AVIATION.......JLA

NWS GRB Office Area Forecast Discussion