118 

FXUS63 KGRB 051757

AFDGRB



Area Forecast Discussion

National Weather Service Green Bay WI

1257 PM CDT Fri Jun 5 2026



Updated aviation portion for 18Z TAF issuance



.KEY MESSAGES...



- Scattered showers and storms are expected over much of the area

  this afternoon and evening. Some storms could become strong or

  severe, with damaging winds and up to 1" hail being the main

  concerns. 



- Above normal temperatures persist for the next week. Chance for

  highs in the 90s increases early next week, along with 

  potential for moderate to major heat-related impacts.



&&



.DISCUSSION...

Issued at 109 AM CDT Fri Jun 5 2026



Rain/storm chances... Severe weather threat remains on track for

this afternoon/evening as driving shortwave treks over the

northern Plains and cold FROPA makes it into Wisconsin. Subsidence

behind a line of showers over northeast Wisconsin late tonight 

has been efficient in clearing out skies to our west, which, if 

trends hold, would be conducive for destabilization this 

afternoon and evening. Increasing bulk shear (30 to 35 knots) and

steepening lapse rates (7 to 9 C/km) occur during this time as 

well, which could lead to development of some stronger updrafts as

they coincide with peak heating. CAMs seem to latch onto a signal

for convective initiation to occur somewhere over central 

Minnesota late this morning, before rapid upscale growth into a 

line segment/QLCS occurs Friday afternoon before reaching 

northeast Wisconsin. In this scenario, damaging wind gusts would 

be the primary concern as the low-level jet ramps up. Hail up to 

1" would be a secondary concern given steep lapse rates and 

elongated hodographs. Periods of moderate to heavy rain will 

accompany any stronger convection as PWATs reach around 1.5" (90 

to 95th percentile), with WPC highlighting mainly east-central

Wisconsin in their Excessive Rainfall Outlook.



Temperatures... Temperatures will remain well above average over 

the course of the next week as synoptic flow re-amplifies and 

building heat ridge/Hudson Bay high set us up under southerly flow

regime. Potential for heat-related impacts drastically increases 

during the early to middle part of next week, with probabilities 

for 90-degree highs sitting at a widespread 50 to 80%. Ample 

moisture transport from an open Gulf will likewise cause dewpoints

to rise solidly into the 60s, which would put us under a level 2 

out of 4 (moderate) risk for heat-related impacts early next week,

increasing to level 3 out of 4 (major) by mid-week. Warmest

periods look to be Wednesday and Thursday afternoons, when heat

indices are forecast to exceed 100 degrees across portions of

central Wisconsin to the Fox Valley. Though still too soon to say

with certainty, will need to monitor the potential for headlines

as we head into early next week.



Extended... Accompanying the heat and humidity next week will be 

a reservoir of instability that builds over much of the upper

Midwest. However, predictability for any rain/storm chances 

remains low this far out as mid-level ridge sits right overhead.

Most of the ridge rider activity looks to stay off to our west, 

so convective initiation in our neck of the woods would likely 

hinge on smaller scale forcing mechanisms given the general 

absence of upper support. This being said, cannot rule out

periodic chances for some stronger diurnal storms given the 

magnitude of destabilization likely to occur during peak heating.



&&



.AVIATION...for 18Z TAF Issuance

Issued at 1257 PM CDT Fri Jun 5 2026



Lingering MVFR/VFR stratus and cumulus clouds will affect portions

of the region through the afternoon, especially along the Lake

Michigan shoreline and in north-central Wisconsin where increasing

instability has brought back some additional cumulus formation. 



A round of rain and thunderstorms is then anticipated to cross the

region in the late afternoon and evening from west to east,

crossing into Wisconsin out of Minnesota. A few stronger storms 

may be embedded within the line, with some hail potential in the 

early afternoon turning to mostly a wind gust concern by the time 

the storms reach the Fox Valley and lakeshore TAF sites. Exact 

location of the stronger storms remains more uncertain at this

time, so kept the PROB30 group for now, but would expect to see

changes over to TEMPO and possibly prevailing as the storm

trajectories become more certain over the next TAF issuance.



Behind the storms, currently expect some clearing and better

flying conditions going into Saturday, so have VFR return by the

morning hours.



&&



.GRB WATCHES/WARNINGS/ADVISORIES...

None.



&&



$$



DISCUSSION.....Goodin

AVIATION.......Uhlmann