667
FXUS63 KGRB 281702
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1202 PM CDT Fri Aug 28 2026

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Periods of rain and storms are expected at times from this
  weekend into early next week, starting Saturday morning. It is
  too early to determine the severe storm potential at this time.

- Temperatures will warm above normal late this weekend into early
  next week with the return of more humid conditions.

&&

.DISCUSSION...
Issued at 239 AM CDT Fri Aug 28 2026

This morning through Tonight...High pressure will reside over the
area during this forecast period, resulting in dry conditions under
mostly clear/sunny to partly cloudy skies. Fog will struggle to
develop early this morning due to the scattered cloud cover, but
cannot rule out a few patches of fog to develop across portions of
central and north-central WI this morning where longer breaks in the
clouds occur. Any fog would burn off soon after sunrise. There
appears to be another signal for fog to develop in far northeast WI
tonight before high clouds move into the area.

Rest of the forecast...The high pressure will depart the region
tonight leaving return flow and mid-level zonal flow in its wake for
the weekend. The first of the shortwaves riding the flow will move
over the area on Saturday, as southwest flow allows moisture to
increase over the area with PWATs of 1.5-1.75 inches. Parameters for
thunderstorms and severe weather on Saturday are rather lacking, so
brief heavy rainfall will be the main impact from Saturday`s
shortwave. The rain will move from the west Saturday morning and
gradually slide east through Saturday night into early Sunday
morning. NBM probs for 0.50" or more of rain are greatest in central
WI at 35-55%, with generally 15-35% elsewhere. Additional periods of
rain and storms are possible throughout the remainder of the weekend
into Monday, but details on when and where they will occur are still
uncertain. However, a washout is not expected as there appears to be
dry periods. Determining the severity of the storms is still too
difficult to determine at this time due to the timing and placement
differences, but generally there still appears to be some agreement
in the instability peaking on Sunday afternoon and Monday afternoon
somewhere across the state.

Beyond Monday, models are in some agreement in the zonal flow
continuing through midweek with a nearly stationary boundary setting
up somewhere across the state. Wherever this boundary sets up, there
will be a risk of heavy rainfall with any shortwave that moves along
the zonal flow.

Temperatures...Highs will be a few degrees above normal today, but
will fall to a few degrees below normal on Saturday due to the
expected rainfall and cloud cover. Temperatures will then rise above
normal Sunday through early next week aided by the southerly low-
level flow. This flow will also result in the return of humid
weather on Sunday and Monday as dew points increase into the upper
60s and low 70s, mainly in central and east-central WI.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1202 PM CDT Fri Aug 28 2026

High pressure will maintain VFR conditions with light winds under
10 kts through tonight. Fair-weather clouds above 5 kft will
dissipate early this evening, followed by thickening mid and high
clouds overnight. Patchy fog is possible over far northeast WI
late tonight, with minimal impacts to the terminals.

Rain chances increase Saturday morning as a weak shortwave and
warm advection move in. Rain arrives at KRHI/KAUW/KCWA between
10Z-12Z Sat, reaching KGRB/KATW/KMTW around 14Z-16Z Sat. MVFR
ceilings and visibilities will develop in steady rain, highlighted
with TEMPO groups. Thunder chance remains 

NWS GRB Office Area Forecast Discussion