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000
FXUS63 KGRB 230322
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1022 PM CDT Mon Apr 22 2024

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- There is a chance of thunderstorms Tuesday, but severe storms
  are not expected.

- Thunderstorms are possible Friday afternoon through Saturday. It
  is too early to determine whether they might be severe.

&&

.DISCUSSION...
Issued at 308 PM CDT Mon Apr 22 2024

Short Term...Tonight and Tuesday

Gusty southwest winds and sunny skies for much of the morning
allowed temperatures to surge into the 60s fairly readily today,
with a few places now approaching the upper 60s this afternoon.
Combined with the wind and warmth, low dewpoints, especially over
the sandy soil regions, brought relative humidity readings into
the 20% range and a few into the upper teens. Suffice to say,
would expect elevated fire weather conditions to persist through
the late afternoon and evening before moderating wind gusts and
lowering temperatures arrive.

This evening, a relatively fast moving cold front will cross the
region, keeping skies cloudy through the evening and early
overnight and possibly bringing in a round of showers. The
aforementioned dry conditions will be an obstacle for any rain to
overcome and will likely limit the overall rainfall that can reach
the surface. No thunder is expected at this time with these
showers and any rain that does get to the surface is generally
expected to be less than a tenth of an inch. Subsidence behind the
cold front will clear out showers fairly quickly, bringing back
dry conditions and clearing skies.

Tuesday, a stronger secondary cold front will push into the region
by the late morning to afternoon bringing another round of active
weather. This front will bring a round of fairly decent
frontogenesis in the mid- levels and strong vorticity advection.
Most models develop around 400-800 MUCAPE ahead of the frontal
passage as well, so all together some thunder does seem likely
Tuesday afternoon, with the highest potential across central
Wisconsin to the Fox Valley. Although severe weather is not
expected, some occasional gusty winds are still possible. The
cold air advection behind the front will be strong enough to begin
lowering temperatures at the surface, even during the afternoon.
As a result, high temperatures have a fairly wide spread tomorrow
from the lower 50s near the Upper Peninsula border to the middle
to upper 60s near the southern portion of the Fox Valley. Colder
air filling in behind the front may even produce a few snowflakes
across the north before precipitation moves out of the region.

Long Term...Tuesday Night Through Monday

Scattered showers and isolated thunderstorms should
end over east central Wisconsin Tuesday evening, with clearing
overnight as a 1030mb surface high over Hudson`s Bay begins to
move south into the Great Lakes. The north northeast flow around
the high will bring very dry air into Wisconsin Wednesday, with
afternoon relative humidity of 15 to 25 percent possible. Winds
will be rather light, and temperatures cool, which should lessen
the fire weather threat to some degree.

Winds will become south and temperatures warm as the high moves
off to the east Thursday and Friday. Showers and thunderstorms
will arrive Friday afternoon and continue into Saturday as a
surface low moves northeast across the Plains states.

Temperatures will be below normal Wednesday, near average Thursday
and Friday, and above normal Saturday and Sunday.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1002 PM CDT Mon Apr 22 2024

Evening showers will shift east of the forecast area by issuance
time, followed by a dry period and partial clearing overnight
into early Tuesday. Surface winds will subside and LLWS will
gradually end from west to east overnight.

On Tuesday, a strong cold frontal passage will generate numerous
showers and scattered thunderstorms in a marginally unstable air
mass, especially in the afternoon and early evening. Will continue
to highlight the best two-hour window for thunderstorms at all of
the TAF sites, except RHI. Ceilings may drop to MVFR behind the
cold front in far northern WI, but models have backed off a bit on
the low ceilings.

West to northwest winds will gradually increase on Tuesday, then
abruptly turn north and become gusty as the cold front moves
through during the afternoon and early evening. The strongest
winds will likely occur in the Fox Valley and lakeshore areas.

&&

.FIRE WEATHER...
Issued at 308 PM CDT Mon Apr 22 2024

Milder temperatures in the 60s, gustier southwest winds of 15 to
25 mph with gusts up to 30 mph, and low relative humidity values
of 20 to 30 percent will keep elevated fire weather conditions
in place through early this evening, until showers advect into
the area from the west.

Another period of elevated fire weather conditions is possible
Wednesday and Thursday, as a dry airmass moves into the region.
Afternoon RH values of 25 to 30 percent are possible on
Wednesday, but cooler temps are anticipated in the low 50s. On
Thursday, RH values will be slightly higher between 25 to
35 percent, and temps will also be slightly higher in the mid 50s
to low 60s. But, due to the proximity of the prevailing high
pressure system, winds will be below critical levels on both
days.

&&

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

&&

$$

DISCUSSION.....Uhlmann/RDM
AVIATION.......Kieckbusch
FIRE WEATHER...Uhlmann