817
FXUS63 KGRB 172304
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
604 PM CDT Thu Jul 17 2025

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Cooler and less humid conditions expected through Friday.
  Temperatures and humidity increase some over the weekend.

- An active pattern is expected Friday night through the middle of
  next week with periodic chances of showers and thunderstorms.
  Stronger storms and heavy rain are possible at times.

&&

.DISCUSSION...
Issued at 223 PM CDT Thu Jul 17 2025

Cooler and much less humid conditions prevailed this afternoon
as temperatures were only in the upper 60s to lower 70s.
Comfortable dewpoints in the middle 40s to middle 50s were
reported as well.

For tonight, the fair weather cumulus will disappear this evening
with mostly clear skies continuing overnight. Did add some patchy
fog to the forecast due to the recent rain yesterday and expected
clear skies and light winds tonight. An upper level disturbance
will move into far northern Wisconsin Friday afternoon, bringing a
chance of showers in this region. Little or no CAPE and poor
700/500mb lapse rates supportive of not adding thunder to the
forecast. The next chance for a widespread rainfall will be Friday
night into Saturday morning as a 500mb trough swings across the
western Great Lakes. The risk for severe storms at this point is
very low. High pressure prevails Saturday night through Sunday
night.

Beyond Sunday night, the westerlies will remain along the
U.S./Canadian border next week. With the expected weather
pattern, suspect there will be several thunderstorms complexes
moving across the central United States during this time frame.
Placement and timing of these complexes remains low as the models
continue to show differing solutions from run to run, and amongst
the GFS/Canadian/ECMWF solutions. If there was anyone time period
to focus at the moment, it would be Wednesday into Wednesday
night period for stronger storms and locally heavy rain. Will have
to wait and see how it plays out. Temperatures likely to be at or
above normal much of next week.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 604 PM CDT Thu Jul 17 2025

Scattered cumulus clouds based around 45-50kft are lingering over
the region early this evening. Expect those clouds to clear out over
the next few hours with mostly clear skies expected overnight. As
winds go calm tonight there is a low-end (10-15%) chance for patchy
ground fog across the Wisconsin River Valley, but confidence that
fog will impact any TAF sites is too low to include in the 00Z TAFs.

Friday a scattered cumulus field bases 40-50 kft may again develop,
south of a GRB to ISW line during the early afternoon. Mid and high
clouds will also start to push back in from the west ahead of a
chance for showers arriving during the evening. Beyond the TAF
period cigs may lover to MVFR across northern WI Friday evening as
more steady showers push into the region, primarily impacting RHI.

&&

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

&&

$$

DISCUSSION.....Eckberg
AVIATION.......GK