242
FXUS63 KGRB 052330
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
630 PM CDT Sun Jul 5 2026

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Dry conditions through Tuesday morning, with the exception of a
  stray shower this afternoon and evening in central and northern
  WI. Widespread shower/storm chances (60-85%) return midweek
  with the potential for heavy rain and flooding.

- Temperatures rising slightly above normal for the start of the
  work week, along with increasing humidity levels.

&&

.DISCUSSION...
Issued at 230 PM CDT Sun Jul 5 2026

This afternoon into Monday...a quiet summer afternoon in process
across the region. A weak mid-level shortwave/trough does reside
over the area, but the lack of instability and prevailing
northeast winds ushering in drier air has fended off any shower
activity so far. As we reach peak heating, still can`t rule out a
diurnally driven stray shower/sprinkle or storm in central or
northern WI, but chances are slightly higher as you work into
west-central WI. Any activity will fade after sunset, with dry
conditions expected overnight into Monday as surface high pressure
and upper level ridging build into the Great Lakes. The clear
skies and light winds tonight may allow for some patchy fog to
develop, especially across central and northern WI.

Rest of the forecast...upper level flow turns more zonal Tuesday
into Wednesday, with embedded shortwaves and a stalled frontal
boundary bringing rounds of showers/storms to the region. The
first shortwave arrives Tuesday afternoon into early Wednesday,
producing showers and storms, especially across northern WI. The
second shortwave, along with the passage of the frontal boundary,
is forecast to arrive late Wednesday into Thursday, with another
round of showers/storms likely. This set up will favor periods of
heavy rain and potential flooding, as impressive moisture will be
pooling south of the boundary (PWATs approaching 2") and
repeated/training rounds of storms moving along the east/west
situated boundary. Some hints from the ECMWF Extreme Forecast
Index of a heavy rain/flooding event, but it is focusing more on
the DLH area right now. Trends on where the heaviest rain will
fall will need to be monitored along with the flooding threat. The
Excessive Rainfall Outlook from WPC continues to highlight the
flooding risk with most of the area in a Slight Risk (level 2 of
4). A little too early to determine severe weather potential/timing,
but with bulk shear up to 35 kts and MUCAPEs likely near 2000
J/kg, there will at least be a low-end chance of severe storms,
but timing/cloud cover and what happens upstream will all factor
in.

Temperatures...High temps will creep to a little above normal to
start the work week, then drop back to near normal towards the
end of the week. Widespread clouds/rain, especially in the
afternoon, could hold readings below current forecast values
midweek. After a pleasant summer day with not too much mugginess,
dewpoints will slowly climb through midweek, with some mid to
upper 60 dewpoints expected by Thursday.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 521 PM CDT Sun Jul 5 2026

SCT daytime cu field persists early this evening, though will
continue to scatter out within the next couple of hours. A stray
shower remains possible over central Wisconsin through this
evening, though opted not to include in the TAF (< 30% chance).
Otherwise, decoupling winds and mostly clear skies may result in
patchy ground fog developing late tonight into Monday morning,
though confidence is low in fog coverage and density. Overall,
VFR conditions prevail through the TAF period.

Winds will continue to become light and variable overnight, eventually
turning northeasterly by Monday morning. Prevailing winds should
remain under 10 knots for the duration of the TAF period.

&&

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

&&

$$

DISCUSSION.....Bersch
AVIATION.......Goodin

NWS GRB Office Area Forecast Discussion