251 
FXUS63 KGRB 161655
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1155 AM CDT Mon Jun 16 2025

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- A warm, humid, and stormy period is expected through mid-week,
  and again toward Friday/Saturday. Strong to severe storms and
  heavy rainfall will be possible at times. Any areas that receive
  multiple rounds of heavy rainfall will be under the threat for 
  flooding.

&&

.DISCUSSION...
Issued at 306 AM CDT Mon Jun 16 2025

The area will get into the warm sector today as a low pressure 
system develops across the northern CONUS. This will allow 
temperatures to soar as dew points rise into the 60s, providing 
for a warm and humid air mass across the western Great Lakes. 
There may be some showers and a few thunderstorms ahead of the 
approaching warm front this morning. Another round of showers and
thunderstorms is then possible later this afternoon into the
overnight hours as the cold front tracks through the region. 
MUCAPEs will only around 500 J/kg this morning with 10 knots of
bulk shear; therefore, these storms are not expected to be 
severe.

An MCS developing across the Dakotas and Minnesota today is 
progged to push east coincident with the cold front tonight.
Recent model runs take the bulk of this activity northeast over
Lake Superior tonight with some models tracking the storms through
northern Wisconsin. This recent trend from the models diverging
from each other lends itself to very low confidence that the area
will get these storms. If storms can make it into the area the 
best chance for strong to severe storms will be west of the Fox 
Valley this evening with 1000-2000 J/kg along with 30-40 knots of 
bulk shear.

Another MCS is forecast to develop on Tuesday and track east 
Tuesday night. While the models generally take this system to our 
south, there are some models that do graze portions of central and
east-central Wisconsin with this system Tuesday night as MUCAPEs 
will be as high as 1000 J/kg with 30 knots of effective shear.
Given the model trends in keeping this system south of the area
for the most part confidence in strong to severe storms reaching
the area this period is also low. 

There will be another chance for strong to severe storms Wednesday
into Wednesday night as a low pressure system tracks from Iowa
through the central Great Lakes. The threat for severe weather
will once again depend on the timing and track of the low with the
best chance for strong to severe storms from the Fox Valley east
to the lakeshore as these areas will be closer to the best
instability and forcing.

There will be additional opportunities for showers and
thunderstorms through the rest of the week into the weekend as
several additional lows track through the zonal flow in place
across the northern CONUS. The next best chance for strong to
severe storms appears to still be Friday night as the models are
honing in on a complex of storms developing ahead of a surging
warm front with MUCAPEs around 1000 J/kg and 50 to 60 knots of
effective shear. Despite this being at the very end of the week,
the models have been keying in on this period for several runs.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1155 AM CDT Mon Jun 16 2025

Confidence is lower than normal over the next 24 hours as weak
upper level disturbances pass over eastern Wisconsin this
afternoon, followed by passage of a cold front tonight. In
general, clusters of showers and thunderstorms have been weakening
this morning and expect this trend to carry over into the
afternoon. These clusters of precipitation have the greatest
potential to impact AUW/CWA. Included a shower mention as 
prevailing thru 20z. May have to expand to RHI and will make a 
last minute decision.

Another round of showers and storms is forecast to move across the
forecast area this evening. Added a 2 hour tempo group at each
terminal which represents the timing with the most confidence.
The strongest storms could contain brief gusty winds to 30 kts and
small hail.

Otherwise, MVFR ceilings over north-central WI this afternoon will
continue into Tuesday morning. Behind the front, MVFR ceilings are
forecast to become more widespread for a time late tonight into
Tuesday morning. Areas of IFR ceilings are possible over north-
central WI, including RHI.

Lastly, low level wind shear is forecast to develop tonight, 
which will dissipate on Tue morning.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION.....Kurimski
AVIATION.......MPC