FXUS63 KGRB 191917

AFDGRB



Area Forecast Discussion

National Weather Service Green Bay WI

217 PM CDT Tue Aug 19 2025



Forecast discussion for routine afternoon forecast issuance



.KEY MESSAGES...



- Patchy dense fog overnight tonight through daybreak on 

  Wednesday, especially central and north-central Wisconsin.



- Isolated showers are possible at times through Wednesday. The

  rest of the week will be dry with the next chance for showers

  and thunderstorms Friday into Friday night. Severe storms are

  not expected.



- Temperatures will be around normal for much of the upcoming week,

  with the potential for well below normal temperatures late in 

  the weekend into early next week.



&&



.DISCUSSION...

Issued at 211 PM CDT Tue Aug 19 2025



Low amplitude shortwave trough in northwest flow along with

ongoing cold air advection will result in small chances for 

showers through Wednesday. High pressure centered over northern 

MN and western Lake Superior through Wednesday with low pressure

crossing the lower Great Lakes will lead to general northeast

low-level winds, with convergence maximized near bay of Green Bay

and Lake Michigan. It will be in this zone, where the shower

chances will be maximized on Wednesday. Rainfall amounts will be 

very light, well under 0.25 inch through Wednesday. Given the 

cooler air flowing across the lakes (+12c at 850mb/5kft), took a

glace at potential lake effect processes aiding in the showers, 

but even with water temps on the lake and the bay around 68-72f

(20-21c), delta t/s stay below threshold of 13c which is typically

what is needed to see even a weaker lake response. This also keeps

us out of any range for potential waterspouts, for now.

 

Other issue through Wednesday will be patchy dense fog late tonight

into early Wednesday. Using the HREF data, highest risk of visibility

less than 1 mile (30-60%) is located over central and north-central

WI. Added mention of patchy dense fog to the HWO. Temps tonight 

will drop into the 50s north-central into far northeast WI. Highs

on Tuesday will mostly rise to the middle to upper 70s.



Looking ahead, after a couple days of dry weather later Wed through

Thu thanks to Canadian high pressure, approaching cold front brings

next chance of showers and storms across the region on Friday.

Instability and shear shown by LREF could support isolated strong

storm if this fropa occurs during max heating on Friday afternoon,

but severe storms are not expected. Behind the front, next weekend

looks more fall-like with highs by next Sunday perhaps not even 

reaching 70. Skies will partly to mostly cloudy with cu and 

stratocu and it may be breezy at times. Forecast currently will 

carry small chance of showers on Sunday, especially north and 

northeast. Pattern would suggest that later forecasts may end up 

showing higher chance for showers especially Saturday over the

north and on Sunday for all areas, along with an increase in 

cloud cover. Further increase in the showers may be due to lake 

effect as 850mb temps bottom out at 5-6c. The taste of fall will

last through early next week.



&&



.AVIATION...for 18Z TAF Issuance

Issued at 1244 PM CDT Tue Aug 19 2025



Ceilings are grudgingly lifting to mainly MVFR. Expect additional

improvement to lower VFR by late afternoon. A few showers may occur

at RHI into early evening. Later tonight, another round of low CIGS

are expected, with LIFR-IFR category central to north-central and

MVFR elsewhere. Fog expected with IFR-MVFR VSBY central to north-

central WI, with VSBY as low as LIFR over north-central (RHI). On

Wednesday, even once the fog lifts, expect low CIGS to persist 

through the rest of TAF period. A few showers could occur on Wed

morning at MTW.



&&



.GRB WATCHES/WARNINGS/ADVISORIES...

None.



&&



$$



DISCUSSION.....JLA

AVIATION.......JLA