FXUS63 KGRB 072348
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
648 PM CDT Tue Jul 7 2026

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- 20-30% chance of showers and thunderstorms this afternoon and
  evening across parts of north-central and far northeast 
  Wisconsin.

- There is a 15-30% chance of severe thunderstorms (15-30% 
  chance) and heavy rain (15% chance) on Wednesday afternoon and 
  evening, primarily across central and east- central Wisconsin. 
  Damaging winds and localized flooding will be the main threats, 
  but isolated large hail and a tornado are also possible.

- Monitoring the potential for excessive heat early next week as
  high temperatures rise into the low to middle 90s on Monday and
  Tuesday.

&&

.DISCUSSION...
Issued at 152 PM CDT Tue Jul 7 2026

The latest RAP analysis and satellite/radar imagery show a weak 
sfc trough across northeast Wisconsin early this afternoon. 
Dewpoints have been creeping up this morning and are comfortably 
in the low to middle 60s. Meanwhile, a weak cold front is draped 
across western Lake Superior and central Minnesota, with upstream 
convective clusters developing across the northern Plains that 
will eventually influence our weather over the next 24 TO 36
hours.

Scattered Afternoon/Evening Storms: With further daytime heating,
instability is projected to rise into the 1000-1500 j/kg range 
this afternoon over north-central and far northeast Wisconsin. Low
level moisture convergence will be favorable for pop up showers 
and storms along a weak surface trough, with 3-8 PM being the 
most favored time period. Brief wind gusts in excess of 40 mph and
heavy downpours will be possible with any showers today before 
dissipating around mid- evening.

Wednesday Afternoon and Evening Severe/Heavy Rain Risk: Attention
turns to late tonight when the upstream cold front sags into 
northern Wisconsin, bringing clusters of thunderstorms across 
northern Wisconsin late tonight into Wednesday morning. This first
round should exit by late morning, but its evolution (coverage &
timing) will help determine the severe potential for late 
afternoon and evening. There is potential for outflow to create an
effective front over central and east-central Wisconsin, but 
considerable uncertainty exists how this will evolve. If the 
atmosphere can recover, potential instability from 1500-2500 j/kg 
and effective shear of 25 to 30 kts will support organized storms 
from 3-9 PM. Damaging winds will be the primary threat, but an 
organized storm could also produce isolated large hail and an 
isolated tornado. Locally heavy rainfall of 2-4 inches is under a
15% chance, with the greatest potential across central and east- 
central Wisconsin.

Excessive Heat Potential Early Next Week: After the threat of
strong storms ends Wednesday night, the slow moving front sags
south on Thursday, leaving only light rain potential over central
and east-central Wisconsin. High pressure then moves across the
area on Friday through the weekend. By early next week, we will be
monitoring the potential for excessive heat. A potent sub-tropical
ridge is expected to build over the northern Plains and western
Great Lakes in the 95-100 percentile. There is a 60-80% chance of
850 mb temps greater than 20C on Monday and Tuesday, which would
equate to surface highs in the low to mid 90s.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 648 PM CDT Tue Jul 7 2026

VFR conditions will continue into the evening hours, with a few
cumulus clouds hanging around with increasing mid and high 
clouds. A stray shower will remain possible over mainly northern 
WI through around sunset, but activity so far this afternoon has 
been pretty limited, so will not include at RHI.

As a cold front slowly sags into the region, clusters of showers 
and storms and lower clouds are likely to impact the region from 
09Z-16Z, with an additional round Wednesday afternoon/evening. 
Continued to use TEMPO groups at all TAF sites to highlight the 
greatest potential for storms, but timing details will need to be 
fine-tuned as exact timing of the storms becomes clearer. MVFR 
ceilings and visibilities (locally IFR) will be possible within 
the shower/storm activity. 

Winds will remain mainly under 5 kts tonight, then become south to
southwest Wednesday morning, with a few gusts around 15 kts. Winds
will shift to the north and become variable Wednesday afternoon
and evening behind the front.

&&

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

&&

$$

DISCUSSION.....MPC
AVIATION.......Bersch