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FXUS63 KGRB 160350 AAA

AFDGRB



Area Forecast Discussion

National Weather Service Green Bay WI 

1050 PM CDT Thu May 15 2025



.KEY MESSAGES...



- Gusty southwest winds are expected Friday, with highest gusts

  up to 40 mph in the Fox Valley. 



- Another period of showers and thunderstorms are expected

  Friday afternoon. Damaging wind gusts may be possible with any

  stronger storm.



&&



.DISCUSSION...



UPDATE...Issued at 936 PM CDT Thu May 15 2025



The line of storms just exited northeast WI. Scattered showers

with a few lightning strikes are still ongoing over north

central WI due to continued vorticity advection with the

spinning closed low that is now over eastern North Dakota. 



The southwest winds are gusty upstream with that lobe of

vorticity pushing into central WI, which is due to momentum

transfer. It looks like winds will taper off through the

overnight hours with weaker mixing. But as soon as the sun

rises, expect the gusty winds to kick in once again. 



Previous Discussion...Issued at 304 PM CDT Thu May 15 2025



The Rest of this Afternoon through Friday Night:



A broken line of cellular storms has broken out, currently from

Eau Claire down to Madison WI. This is line is expected to

develop further and ramp up in intensity this evening. Hail and

gusty winds are expected, owing to SBCAPE around 2500 J/kg amid

effective shear around 40 knots. A couple tornadoes also look 

possible, given effective SRH values around 200 m2/s2 over much

of NE WI, and an effective warm front parked from the Fox 

Valley up through Marathon and Lincoln County. The peak timing

for storms looks to be from 5pm through 8pm this evening as the

broken line moves northeast. A Tornado Watch is out from now

through 10pm over much of our CWA.



Storms will quickly move through and a dry punch aloft will

clear out skies fairly quickly behind the storms. There will be

a bit of a lull overnight, but tomorrow, enhanced mixing will

lead to gusty southwest winds with some scattered gusts to 40

mph. A secondary shortwave pivoting around an upper level low 

and lingering moisture will squeeze out some more scattered 

thunderstorm activity in the afternoon. Very dry low levels and 

the high based nature of the storms will cause the potential for

gusty winds with any storms that get established enough in the 

environment.



Saturday through Wednesday



The upper low will linger into Saturday. Cooler conditions are

expected due to clouds and the cooler air aloft and highs will

top out in the low to mid 60. Diurnally driven scattered 

showers may occur through the day. This upper low should move

east on Sunday, restoring relative high pressure, but clouds

will likely linger along with cooler temperatures as winds will

come around to northeasterly. By late in the extended period, a

large low pressure system is expected to approach the upper

Midwest Monday into Tuesday, bringing a prolonged period of

showery rain and clouds to the area. Winds will remain 

northeasterly off of the lake, keeping our CWA cool with highs

in the 50s.



&&



.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...

Updated at 1050 PM CDT Thu May 15 2025



While strong thunderstorms have departed late this evening and a 

lull in the weather is expected overnight, expect flight conditions 

to deteriorate on Friday as low pressure slowly crosses the region.



South to southwest winds will become strong and gusty by mid to late 

Friday morning with gusts of 30 to 35 kts likely.  These gusty winds 

will diminish on Friday evening.



Low level wind shear will likely develop across the region late 

tonight and continue through Friday morning.



Scattered showers and thunderstorms are forecast to develop on 

Friday afternoon.  A few strong storms are possible that could 

produce wind gusts in excess of 45 kts.



Ceilings are forecast to fall to MVFR on Friday evening with another 

round of showers moving across the region.





&&



.MARINE...

Updated at 936 PM CDT Thu May 15 2025



A small craft advisory continues into tonight. The southeast

winds are switching to southwest. There should be a period of

gusty southwest winds overnight, but lower confidence in them

occurring over the lakeshore vs. inland. Therefore, we will

probably allow the Small craft advy expire. We will need another

small craft advisory for tomorrow as gusty southwesterly winds 

are expected to become gusty during the daytime hours.



&&



.GRB WATCHES/WARNINGS/ADVISORIES...

WI...None.

MARINE...Small Craft Advisory until 1 AM CDT Friday for LMZ522.

     Small Craft Advisory until 11 PM CDT this evening for LMZ542-

     543.



&&



$$



DISCUSSION...MRC

AVIATION...MPC

MARINE...MRC