FXUS63 KGRB 030903

AFDGRB



Area Forecast Discussion

National Weather Service Green Bay WI

403 AM CDT Thu Jul 3 2025



Forecast discussion for routine morning forecast issuance



.KEY MESSAGES...



- Continued potential for showers and thunderstorms late tonight

  into Friday (July 4th), and Saturday through Sunday. The

  greatest chance for widespread showers and thunderstorms will

  occur Saturday and Saturday night. A low-end (Marginal) severe

  threat exists through the period, and there is potential for 

  heavy rainfall Saturday into Saturday night.



- Temperatures will be above normal through the holiday weekend,

  with very warm and humid conditions expected Friday (July 4th)

  and Saturday.



&&



.DISCUSSION...

Issued at 403 AM CDT Thu Jul 3 2025



A weak boundary was sagging south across the forecast area early

this morning. Along and north of the boundary, partly to mostly

cloudy skies were observed, along with isolated showers. Wherever

clearing had occurred, patchy fog was developing.



Thunderstorm Chances through the Holiday Weekend: The weak front 

is expected to shift southwest of the forecast area this morning,

stall out through the evening, then lift northeast as a warm 

front late tonight into Friday. After a general lull in showers

and thunderstorms (slight chance within the area of higher 

instability in C WI) through this evening, elevated storms are

expected to increase as the warm front pushes northeast. SPC HREF

shows the best concentration of 40+ dBZ paintballs occurring 

across the forecast area late tonight through noon Friday.

Marginal instability and weak shear (around 20 kts) does not bode

well for organized severe weather, but a couple strong storms 

with small hail cannot be ruled out. The convection should start 

to wane during the afternoon as an upper level ridge builds over 

the region and the warm front lifts northeast. Generally dry 

conditions are expected for the Friday evening fireworks displays.



Models have trended a little slower with the weekend cold frontal

passage, with dry conditions prevailing through the overnight

Friday night, and widespread showers and thunderstorms impacting 

the forecast area Saturday into Saturday night. CAPE building to 

1-2K j/kg and modest deep layer shear of 20-30 kts point to a 

marginal severe risk Saturday afternoon and evening. PWATs 

increasing to 2-2.25 inches (200 percent of normal) supports a 

threat of heavy rainfall and localized urban flooding. The slower 

frontal movement leads to a continued chance of showers and storms

into Sunday, especially over the southeast CWA. 



Drier conditions are expected for at least the early part of the 

next work week, as high pressure and much drier air arrives in 

the wake of the front.



Temperatures: Above normal temperatures are expected through

Saturday, followed by near to a little below normal conditions

through the middle of next week. Very warm and muggy conditions

arrive for Friday (July 4th) and linger over eastern WI into Saturday,

with heat indices into the lower to middle 90s. The heat and

humidity will impact outdoor activities for the 4th of July, but

heat indices fall a little short of advisory criteria at this

point.



Smoke: Smoke models show elevated smoke impacting far N/NE WI 

through this afternoon, so have increased sky cover a little to 

account for this. There is a very small chance of near-surface 

smoke in the far north (mainly Vilas County) during the late 

morning and early afternoon, but confidence is too low to add to 

the forecast at this time.



&&



.AVIATION...for 06Z TAF Issuance

Issued at 1131 PM CDT Wed Jul 2 2025



Very isolated showers and storms continued across the region late

this evening. Prior to the start of the 06z TAFs, several

amendments have been made to all TAF sites to account for the 

very isolated convection. For the 06z issuance, have included

TEMPO groups at all sites except GRB and MTW from 06z to 08z to

account for ongoing convection based on radar trends. The 

isolated showers and storms should end around 08-09z, but a few 

may linger beyond 09z.



Fog development looks less impressive across north-central WI

given the continued cloud cover, but anticipate the central WI TAF

sites could still see IFR vsbys late tonight/early Thursday 

morning.



Another SCT cu field looks to develop Thursday afternoon. There is

also potential for isolated showers and storms to develop in

portions of central WI within this cu field for the afternoon, 

but confidence is not high enough to include any showers/storms at

AUW/CWA as models indicate it should stay south of these sites.



&&



.GRB WATCHES/WARNINGS/ADVISORIES...

None.



&&



$$



DISCUSSION.....Kieckbusch

AVIATION.......Kruk