FXUS63 KGRB 261755

AFDGRB



Area Forecast Discussion

National Weather Service Green Bay WI

1255 PM CDT Thu Jun 26 2025



Updated aviation portion for 18Z TAF issuance



.UPDATE...

Issued at 1118 AM CDT Thu Jun 26 2025



Have issued a Flood Watch for Wood, Portage, Waupaca, Waushara and

Winnebago counties from 4 pm today through 4 am Friday. Much of

this area has received 1.5 to 3 inches of rain since Monday, so

soils are saturated. A west to east line of storms is expected to

develop over the watch area as a warm front approaches late this 

afternoon. An additional north to south line of storms will cross 

the area during the evening. Both of these lines will be capable 

of producing torrential rainfall, given PWATs around 2 inches, 

and some elevated instability will support higher rainfall rates 

in storms.



Most models keep the warm front and associated surface based

instability south of the forecast area late this afternoon, but

given the close proximity of the front (shallow stable layer near

the surface), MUCAPE of 500-1000 j/kg and 0-3 km SRH of 200-400 

m2/s2, there is potential for supercells with damaging winds and a

few tornadoes, especially in our far southwest counties. CAMs show

development starting in our far southwest by 4-5 pm.



&&



.KEY MESSAGES...



- There is a marginal risk for severe thunderstorms this afternoon

  through this evening across central and east-central WI. Strong

  wind gusts are expected be the main hazard, with a few weak

  tornados also possible. Another round of strong to severe 

  storms is possible late Sunday afternoon and evening.



- Storms this afternoon and evening may also produce heavy

  rainfall and create a flood risk for saturated low-lying and

  urban areas. A Flood Watch has been issued for central WI and

  the southern Fox Valley for late this afternoon into tonight.

  

- Near/below temperatures continue through Friday, then 

  increasing heat and humidity into the weekend, with highs near 

  90 by Sunday.



&&



.DISCUSSION...

Issued at 354 AM CDT Thu Jun 26 2025



This Morning: A few isolated showers are moving through central WI 

early this morning, however, much of the region has become dry. 

There are also a few pockets of patchy fog mainly across central and 

north-central WI where some of the heaviest rain fell yesterday. The 

dry conditions will be short lived as the next shortwave, over 

southeast SD is already producing scattered storms over western IA. 

As this wave moves east today it will bring another round of rain 

and some strong to severe storms to the region this afternoon.  



Severe Storm and Heavy Rain Potential this Afternoon/Evening: There 

remains a conditions threat for a round of strong to severe storms 

late this afternoon and early evening depending on how far north a 

warm front lifts. 00Z HREF shows this front setting up along or just 

south of HWY 10 this afternoon. CAMs show a few discreet storms 

developing along this front between 1-3PM ahead of a broken line of 

storms forecast to develop over southeast MN/ western WI. This line 

of storms will move east across the state through the late afternoon 

and evening hours. Immediately south of the warm front SBCAPE values 

increase to ~1000-1400 J/kg along with 40-45kts of 0-6km shear. This 

supports at least a marginal risk for severe wind gusts. 

Additionally 0-3km SRH values in the vicinity of the warm front are 

250-400 m2/s2 which does bring the potential for a few weak tornados 

to spin up. HREF 2-5km UH >75 m2/s2 paintballs also show a cluster 

along the 10 HWY 10 corridor late this afternoon/early evening 

highlighting the potential for rotating updrafts.



Given that the heaviest of yesterdays rainfall fell north of HWY 29 

and the expected progressive nature of todays storms flash flood 

potential is going to be primarily tied to storms producing higher 

rainfall rates over the more flood prone urban areas of central WI 

and the Fox Valley. HREF soundings show PWATs ~ 1.8-1.9", which is 

around the climatological max for this time of year, along with a 

deep warm cloud layer. This suggests that torrential downpours 

producing 0.5 to 1" of rain per hour will be possible. Further north 

steady light to moderate rainfall may lead to an addition 0.5 to 

1.5" of rain this afternoon and evening, but given the sandy soil 

don't think the flash flood potential is as great north of HWY 29. 

Will need to monitor some area river gages over the next 24-36 hours 

as a few sites along the Wisconsin River are forecast to reach 

bankfull and Babcock on the Yellow River is forecast to reach minor 

flood stage early Friday morning.



Sunday Thunderstorm Potential: A weak cold front and low amplitude 

upper-level trough are forecast to move across the region late 

Saturday through Sunday. These features will overlap an increasingly 

unstable airmass Sunday with peak SBCAPEs 3000-4000 J/kg. Result 

will likely be a round of scattered thunderstorms with a few 

potentially becoming strong to severe. Weak 0-6km shear ~ 20-30kts 

may be a limiting factor in how organized any storms can become. 

There remains a large degree of uncertainty with the finer details 

during this period. Behind the cold front Sunday a more stable 

airmass will move into the region Monday leading to mostly dry 

conditions to start next week. 



Temperature Trends: Near normal temperatures are expected through 

the end of the week with a warming trend expected this weekend. By 

Sunday most locations are forecast to reach the middle to upper 80s. 

NBM probs show a 40-50% chance for areas in and around the Fox 

Valley to reach 90 degrees Sunday. Prevailing northwest flow will 

develop Monday which help to moderate temperatures back towards 

normal through the early and middle parts of next week.



&&



.AVIATION...for 18Z TAF Issuance

Issued at 1248 PM CDT Thu Jun 26 2025



Widespread IFR/MVFR stratus covered the forecast at issuance time.

Showers and embedded storms were approaching from MN, and these 

will impact our area during the late afternoon and evening.



Slight improvement (rising ceilings) will be observed at the TAF 

sites for the next couple hours, in advance of the rain. Once the

steady moderate to heavy rain arrives, expect IFR conditions to 

expand. After the rain tapers off later tonight, areas of fog and 

very low stratus (LIFR/local VLIFR) will become more widespread. 

Increasing west winds Friday morning will cause ceilings to 

gradually rise to MVFR by midday.



Have added thunderstorms to all TAF sites this evening, with the

exception of RHI. Torrential rainfall and gusty winds may

accompany any storms.



&&



.GRB WATCHES/WARNINGS/ADVISORIES...

Flood Watch from 4 PM CDT this afternoon through late tonight 

for WIZ035>037-045-048.

&&



$$



UPDATE.........Kieckbusch

DISCUSSION.....GK

AVIATION.......Kieckbusch

