059
FXUS63 KGRB 051420 AAA
AFDGRB

Area Forecast Discussion...UPDATED
National Weather Service Green Bay WI
920 AM CDT Wed Aug 5 2026

New Information added to update section

.UPDATE...
Issued at 918 AM CDT Wed Aug 5 2026

Reworked the pops/wx for rest of today as thus far showers have
stayed over southern WI, so lowered pops through late morning.
That said, even as cold front will be south of our area, have
introduced 20-30% chances for scattered showers in the afternoon
especially over east-central WI. Peak timing will be from 2p-5p.
Forcing will be provided by shortwave over northern Iowa and weak
850-600mb frontogenesis enhanced by right entrance of upper jet.

Though cannot rule out thunder as showers will be maximimzed in
coverage during peak heating this afternoon, chances for thunder
will be less than 20% as even MUCAPE will be well under 500 J/kg
held in check by clouds. Risk for scattered showers ends early this
evening.

&&

.KEY MESSAGES...

- Isolated to scattered showers (30 to 50% chance) continue
  through this morning as a slow-moving cold front sinks south.

- Near normal temperatures in the 80s through the weekend.

- Several rounds of showers and storms will be possible Friday
  through Sunday, though confidence in storm timing and severity
  remains low.

&&

.DISCUSSION...
Issued at 1154 PM CDT Tue Aug 4 2026

Shower/storm chances... Latest surface obs show the cold front
draped over southeast Wisconsin early this morning, resulting in
weak radar returns percolating mainly in the Fox Valley eastward.
CAMs show additional shower activity persisting north of the
slow-moving boundary through this afternoon as transient
shortwave energy passes over Wisconsin. A rumble or two of thunder
will be possible mainly over east-central Wisconsin later this
morning, though chances diminish into the afternoon.

Not many changes to speak of regarding late week rain/storm
chances as we remain on the northeast periphery of western
ridge/heat dome. Most long-range models have the reservoir of
instability under the ridge remaining off to our south through the
weekend, which would shunt better chances for more organized
convection to southern Wisconsin and northern Illinois.
Nevertheless, several perturbations embedded within the mean flow
are progged to interact with a surface low as it tracks over the
upper Mississippi Valley, kicking off several rounds of shower and
storm activity across the forecast area Friday afternoon through
Monday. ML guidance continues to paint broad 5 to 15% probs over
the Midwest on Days 4, 5, and 6. Worth mentioning is the fact that
storm predictability remains low this far out, with the synoptic
pattern wont to change over the next couple of days. Will continue
to monitor for any severe weather potential.

Temperatures/smoke... Temperatures to read near normal in the low
to mid 80s through the weekend as upper flow flattens out and
weakens. Humidity levels will be comfortable, with dewpoints
reading mainly in the low 60s. Some elevated smoke may linger
across the area through this evening as the front slowly treks
south, though no significant impacts to visibility or air quality
are expected.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 600 AM CDT Wed Aug 5 2026

Patchy dense ground fog has developed over north-central
Wisconsin in the last couple of hours, resulting in LIFR cigs
in/around RHI early this morning. Have thus opted to include TEMPO
group in the RHI TAF for 1/2 SM vsbys through 14Z, though any fog
should burn off quickly after sunrise.

FEW to SCT showers and low-end VFR cigs are forecast over the
east-central sites through this morning as a slow-moving boundary
sinks south. Have therefore retained TEMPO groups for -SHRA at
GRB, ATW, and MTW. Cigs may briefly drop down to MVFR during this
time, especially near MTW. A rumble or two of thunder would not
be out of the question, though confidence was too low to include
in the TAF. Cigs then gradually lift from northwest to southeast
late this afternoon and evening, with a fair weather cu field at
around 4 to 5k ft developing across the north by around 15 or 16Z.
Clearing trend continues through tonight. Winds will remain light
and variable throughout the TAF period, with gusts to around 10
knots this afternoon.

&&

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

&&

$$

UPDATE.........JLA
DISCUSSION.....Goodin
AVIATION.......Goodin

NWS GRB Office Area Forecast Discussion