000
FXUS63 KGRB 191143
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
643 AM CDT Fri Apr 19 2024

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Gusty west winds of 30 to 40 mph over central to northeast
  Wisconsin will create conditions hazardous to small craft and
  may blow loose objects around today.

- Elevated fire weather conditions are possible on Sunday and
  Monday afternoon due to low relative humidities ranging from 25
  to 30 percent and sustained winds of 10 to 20 mph.

- Next chance for precip returns late Monday through late Tuesday.
  Rain appears to be the main precipitation type, but some snow
  may mix in across the far north on Tuesday.

&&

.DISCUSSION...
Issued at 417 AM CDT Fri Apr 19 2024

Short Term...Today...Tonight...and Saturday

A vigorous mid level shortwave will track through northern
Wisconsin today around the periphery of a broad mid level low
situated across western Ontario. This shortwave will take
advantage of steep low level lapse rates of 8 to 10 C/km all the
way up to around 750 mb. This will produce some convectively
induced showers (20-30 percent chance) west and north of the Fox
Valley today with a bit deeper moisture. The Snow Squall
Parameter indicates there will be the potential for a snow squall
across north-central Wisconsin as this value hovers around 1.
Although snowfall amounts on roadways are expected to be de
minimis given the sun angle this time of year, some light
accumulation on grassy surfaces cannot be ruled out. Further
south, moisture will be limited across east-central Wisconsin with
a sprinkle possible.

Winds at the top of the boundary layer will be fairly high today
around 40 knots, with westerly winds gusting to 30 to 40 mph at
times at the surface given the deep boundary layer and steep low
level lapse rates. The highest winds will be across central and
east- central Wisconsin with higher winds in the boundary layer,
with slightly lower wind speeds across north-central Wisconsin.

Highs today are expected to range from the lower 40s across the
north (with temperatures likely falling into the mid to upper 30s
once the showers begin), to around 50 across east- central
Wisconsin.

Light snow showers or flurries could continue tonight across
north-central Wisconsin as an additional shortwave and mid level
trough swing through the western Great Lakes region. Again some
light accumulation is possible tonight on grassy surfaces, with
some roadways possibly seeing accumulations after sunset. Lows
tonight are expected to range from the middle 20s across the
north, with lows in the lower 30s across east-central Wisconsin.

Cyclonic flow flow will remain across the western Great Lakes
region on Saturday as a weak mid level shortwave tracks through
Wisconsin. Steep low level lapse rates of 8 to 10 C/km will
remain, although only to around 800 mb. Some models are suggesting
another round of showers on Saturday with this shortwave while
others remain dry with less moisture available. Given some models
are signaling precipitation and the presence of a mid level
shortwave will introduce a small chance (10-20 percent) of some
light rain/snow showers or sprinkles/flurries on Saturday. Highs
on Saturday are expected to range from the middle 40s across the
north, with around 50 expected across east-central Wisconsin.

Long Term...Saturday Night Through Thursday

Dry conditions are anticipated for the remainder of the weekend
and through much of Monday as high pressure resides over the area.
The high pressure will gradually exit on Monday and make way for
the next chance for precip Monday night through Tuesday night as a
surface low pressure system and cold front move across the
region. Timing and placement of the low still have a large spread,
in addition to differences in the strength of the upper- level
shortwave/trough. Southwest flow on Monday will lift warmer air
into the region, resulting in rain at the onset of this precip.
There is still some potential for a mix of rain and snow across
the far north on Tuesday, but this will depend on the track of the
surface low. If the low tracks across the central part of the
state, there will be a higher chance for a mix of rain and snow
across the north, but if the low tracks across Upper MI like some
guidance is indicating, only rain would occur. Models with the
latter solution also show steep enough mid-level lapse rates that
a few embedded thunderstorms could occur. Dry conditions return
for midweek following this system as high pressure and ridging
build into the area.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 643 AM CDT Fri Apr 19 2024

Partly to mostly clear skies will become mostly cloudy throughout
the morning with daytime heating with SCT-BKN VFR clouds expected
through the afternoon/evening. Isolated to scattered snow showers
are expected late this morning and afternoon, especially north of
and west of the Fox Valley. Expecting mainly VFR conditions, with
MVFR ceilings/visibilities possible, especially at RHI and
AUW/CWA. Low level instability could produce some brief heavier
snow showers. The snow shower activity will decrease in the
evening across much of the area, but could linger across north-
central Wisconsin.

Surface winds will increase today and remain gusty this afternoon
with west winds gusting to 25-35 knots. Winds will slacken off a
bit tonight, with gusts of 10-20 knots expected.

&&

.FIRE WEATHER...
Issued at 417 AM CDT Fri Apr 19 2024

Confidence is increasing for elevated fire weather conditions
Sunday and Monday, as a dry airmass prevails. Afternoon RH values
will fall into the 25 to 30 percent range on Sunday and into the
25 to 35 percent range on Monday. Winds look to be a little higher
on Sunday, with sustained winds of 15 to 20 mph and gusts up to
30 mph. Sustained winds on Monday to be between 10 to 15 mph, with
gusts up to 25 mph. Not anticipating meeting red flag warning
criteria as temperatures will be below the threshold in the mid
50s to low 60s each day. Will continue to message the elevated
fire weather conditions in the HWO.

&&

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

&&

$$

DISCUSSION.....Kurimski/Kruk
AVIATION.......Kurimski
FIRE WEATHER...Kruk