496
FXUS63 KGRB 050324
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1024 PM CDT Tue Aug 4 2026

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- A few non-severe storms (30-60%) may impact mainly east-
  central into northeast Wisconsin late this afternoon/evening.

- There are intermittent 30-50% chances for storms Friday
  through early next week, but confidence in timing and
  potential severity are low at this time.

&&

.DISCUSSION...
Issued at 1250 PM CDT Tue Aug 4 2026

A cold front will pass southeast across the area this evening into
early Wednesday. Ahead of the front, the HREF surface-based CAPE
reaches ~1000 J/kg across east-central Wisconsin, although
synoptic forcing and deep layer shear are relatively modest.
Isolated to scattered storms may develop ahead of the front, but
the severe weather risk will be quite low. Additional showers
may persist north of the surface boundary overnight into
Wednesday.

A shortwave trough will drag a boundary south towards the area on
Friday with a 20-40% chance of storms. Over the weekend into early
next week, the local area will likely reside on the northern
periphery of a seasonably warm, moist and unstable environment.
Subtle shortwave troughs embedded in the seasonally strong mid-level
westerly flow  will interact with the low-level boundary and
instability to produce rounds of showers and storms across the
Midwest. However, predictability of storms at this range is low in
this type of pattern. Some weather risk could evolve given the
degree of flow aloft, but these trends will need to be evaluated in
coming days as confidence increases with the degree of instability,
timing of shortwaves, and boundary placement.

Otherwise, temperatures will trend seasonably warm late this week
into the weekend. Some smoke aloft from wildfires may lead to hazy
skies at times, but HRRR smoke model suggests low near surface smoke
concentrations through Wednesday.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1024 PM CDT Tue Aug 4 2026

A slow moving cold front will gradually sag south over east-
central WI overnight. Thunderstorm activity should generally
remain south of OSH and MTW overnight but a few scattered showers
will be possible though difficult to have confidence with the
precise timing.

Confidence is increasing, however, for showers to move across
east-central WI on Wednesday morning. As these showers arrive,
ceilings are forecast to fall from VFR into MVFR or high end IFR
range (MTW in particular). Then decreasing clouds are expected
from 20Z Wed to 00z Thu over the Fox Valley and Lakeshore.

Over central and north-central WI, a broken mid-deck will persist
through much of the night. Removed the potential for ground fog
and the IFR visibilities from the previous TAF issuance at RHI. A
widespread fair weather cloud field is then expected to pop with
daytime heating around 16-17z with bases around 4-5 kft.

The clearing trend will continue on Wed night leaving VFR
conditions by the end of the TAF period.

&&

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

&&

$$

DISCUSSION.....JM
AVIATION.......MPC

NWS GRB Office Area Forecast Discussion