513
FXUS63 KGRB 100400
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1100 PM CDT Wed Jul 9 2025

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- Next chances for widespread active weather from Thursday through
  Saturday. Heavy rainfall and a few strong storms will be
  possible on Friday.

- Another round of active weather is possible during the middle
  of next week.

&&

.DISCUSSION...
Issued at 214 PM CDT Wed Jul 9 2025

Tonight into Thursday...Conditions to remain dry through the first
half of Thursday. This afternoon`s clouds stuck around longer than
previously forecast, but should gradually decrease into the evening
as the sun sets. Mostly clear skies and light winds are expected
overnight, which may lead to patchy fog development in some spots by
early Thursday morning. Any fog would burn off soon after sunrise.

End of Week Precip...Models continue to indicate the next
opportunities for precipitation occurring between Thursday and
Saturday as a couple of mid-level shortwaves move through the area.
The first of the shortwaves looks to track over the area on
Thursday. The associated moisture axis will likely struggle to make
eastward progress due to dry air sitting over the eastern half of
the state. But, portions of central and north-central WI could still
see some afternoon/early evening showers and non-severe storms. A
few showers and storms may linger overnight Thursday in central and
east-central WI, but the loss of daytime heating and the weakening
of the shortwave will limit the coverage.

The next mid-level shortwave will begin to move into the area Friday
morning and strengthen with time through Friday night as an upper-
level trough digs over the Northern Plains. This will leave the
forecast area under a southwest flow, lifting an abnormal amount of
moisture into the area with PWATs between 1.75-2.10 inches (150-200%
of normal). There are still discrepancies in the track and timing of
the shortwave and where the axis of heaviest rainfall will occur,
but the overall signal continues to suggest the potential for
localized heavy rainfall somewhere across the forecast area
(probability of exceeding an inch at any one location is 20-30%)
Friday evening/night. The severe potential continues to appear low
given the timing and placement discrepancies and the possibility
of clouds during Friday morning. If anything, forecast soundings
would suggest a heavy rain event (tall, skinny CAPE) with marginal
potential for isolated strong wind gusts (small inverted-Vs).
Precipitation chances look to continue into Saturday as the
aforementioned upper-level trough and associated surface cold
front moves across the Upper Mississippi Valley.

Rest of the extended...Dry conditions are anticipated through the
remainder of the weekend and into early next week. The next chance
for precipitation then looks to occur sometime in the middle of next
week.

Temperatures...While temperatures are expected to remain slightly
above normal throughout the entire forecast period in the 80s,
humidity levels will be the main feature in flux. The late week
system will bring dew points into the upper 60s to low 70s on Friday
and Saturday, leading to the return of humid conditions. However,
heat indices will remain well below any heat headline criteria.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1059 PM CDT Wed Jul 9 2025

Mostly clear skies and light winds overnight, along with lingering
moisture from recent storms, will result in patchy fog. Greatest
risk of fog is at GRB, ATW, MTW where min temps are expected to
fall below the crossover temps. Have continued to cover the fog
potential (MVFR VSBY) with TEMPO groups from 09z-12z. Mid clouds
gradually increase by afternoon at the TAF sites with potential
for showers and storms moving into central WI by early Thursday
evening. For now, placed a PROB30 into AUW/CWA TAFs where models
are most in agreement scattered showers and storms may be around.

Looking ahead, could be a lull in showers and storms later
Thursday evening with loss of daytime heating and resulting
instability, then more showers and storms may move into central
and north-central WI overnight Thursday night.

&&

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

&&

$$

DISCUSSION.....Kruk
AVIATION.......JLA