677
FXUS63 KGRB 120820
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
320 AM CDT Mon May 12 2025

Forecast discussion for routine morning forecast issuance

.KEY MESSAGES...

- Elevated to critical fire weather conditions remain today due to
  dry fuels, low humidity, and winds gusting to around 15 mph. A
  Red Flag Warning has been issued from 12 pm to 9 pm over
  portions of north-central and far northeast Wisconsin.

- There is a medium chance (20-40%) of scattered showers and
  thunderstorms Tuesday and Wednesday, especially during the
  afternoon.

- Higher chances (50-80%) for rain and thunderstorms on Thursday
  and Thursday night. Strong or severe storms will be possible
  with the passage of a cold front.

&&

.DISCUSSION...
Issued at 319 AM CDT Mon May 12 2025

Short Term...Today...Tonight...and Tuesday

Elevated to critical fire weather conditions will continue today
as temperatures warm into the 80s away from the lake with
continued dry dew points across the region. Mostly sunny skies are
expected across the region today with continued dry conditions.

Warm conditions will continue on Tuesday as highs once again reach
the upper 70s to lower 80s. However some modest instability will
combine with a weak shortwave tracking across the region, which
could bring scattered showers and isolated thunderstorms Tuesday
afternoon. Southeasterly surface winds will keep the lakeshore and
Fox Valley cooler than further inland, with highs in the middle
70s across the Fox Valley and 60s near the lakeshore. Any
thunderstorms that develop should not be strong or severe as CAPE
profiles will be very narrow.

Long Term...Tuesday Night Through Sunday

Any lingering showers/storms will end around sunset Tuesday
evening, otherwise dry conditions should prevail Tuesday night.
The 500mb ridging across the western Great Lakes early this week
will weaken as 500mb heights fall, as the closed upper low over
the Tennessee Valley opens up and becomes elongated from
northwest to southeast from Wisconsin into the Tennessee Valley
Wednesday. The combination of daytime heating and some instability
will result in scattered showers and thunderstorms developing on
Wednesday, especially during the afternoon. Surface dewpoints will
be several degrees higher compared to Tuesday as southerly winds
bring some low level moisture into the area. Any showers or
storms should end around sunset Wednesday evening.

The main concern during this period will be the potential for
strong or severe thunderstorms on Thursday. The previous Day 5
outlook from the Storm Prediction Center had portions of central
and east-central outlined for the potential for severe weather.
The new Day 4 Outlook from SPC will be issued a little later
this morning. Otherwise, the latest Canadian/ECMWF and the NAM (up
to 84 hours) indicated a slower trend in the arrival of the front
and storms. The latest ECMWF had storms arriving across central
Wisconsin during the mid to late afternoon and would not reach
northeast Wisconsin until the evening hours. 0-6 km shear values
a little stronger tonight (40-50 kts) off the ECMWF/Canadian
model, and were even stronger on the GFS model. Southeast flow
off Lake Michigan will bring a more stable marine layer into
east-central and northeast Wisconsin. Models are indicating
a ribbon of CAPE between 1,000 and 2,000 J/KG ahead of the front.
With the more stable southeast flow off Lake Michigan, the area
of CAPE near 2,000 J/KG will get pinched off across northeast
Wisconsin. Damaging winds will be the main severe weather risk
although large hail can`t be ruled out.

After the passage of the cold front, a dry slot will move across
the area later Thursday night, bringing dry conditions to much of
the are. It will be windy/blustery. A chance of showers will
continue across the far north later Thursday night closer to the
upper low. The chance of showers continues across the entire
area on Friday as the upper low moves across the western Great
Lakes. Above normal temperatures will continue through Thursday,
returning closer to normal on Friday and then become below normal
next weekend. Looking at some of the temperatures spreads across
the north, it will be cool with highs in the 50s, with the lowest
guidance values only in the lower 50s at Land O"Lakes. Breezy
or windy conditions are expected Friday into Saturday. Gusty
southwest winds are expected on Friday and then from the
west/northwest on Saturday.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1008 PM CDT Sun May 11 2025

VFR flying conditions are expected through the TAF period with
mainly clear skies. South winds will subside around sunset.
Similar afternoon gusts are forecast on Monday.

&&

.FIRE WEATHER...
Issued at 319 AM CDT Mon May 12 2025

Temperatures will be warmer today, as highs are expected to soar
into the 80s. Continued dry dew points will mean relative humidity
values will once again plummet to 15 to 25 percent across northern
Wisconsin and 20 to 30 percent across the rest of the area west
of the Fox Valley. Fuels will continue to be dry, with southerly
winds of 10 to 20 mph. Therefore, will upgrade the current Fire
Weather Watch to a Red Flag Warning given the warm temperatures,
low RH values, and dry fuels. The rest of the area west of the Fox
Valley will get an SPS like yesterday.

Warm temperatures will continue across the region on Tuesday;
however, dew points will rise even further as moisture advects
into the region. Relative humidity values are expected to recover
into the 30s Tuesday afternoon across north-central Wisconsin as
winds remain light.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from noon today to 9 PM CDT this evening for
WIZ005-010>013-018-019.
&&

$$

DISCUSSION.....Kurimski/Eckberg
AVIATION.......Kotenberg
FIRE WEATHER...Kurimski