627
FXUS63 KGRB 032312
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
612 PM CDT Fri May 3 2024

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Scattered showers and isolated thunderstorms are expected
  Saturday into Saturday evening, with additional showers and
  thunderstorms Tuesday through Wednesday.

- A few rivers will remain at or reach bankfull stage into the
  weekend.

&&

.DISCUSSION...
Issued at 340 PM CDT Fri May 3 2024

Short Term...Tonight and Saturday

Deep mixing allowed temperatures to soar into the middle 60s to
lower 70s, caused winds to gust to 25 to 35 mph over far N WI, and
resulted in pockets of low relative humidity in the sandy soil
regions of northern and central WI this afternoon.

Mostly clear skies will give way to a gradual increase in mid and
high level clouds overnight, but dry conditions will prevail.
Considered the possibility of patchy fog overnight, but a well-
mixed air mass, increasing boundary layer winds overnight and
shorter spring night argued against any mention at this time. Look
for low temperatures to drop into the 40s.

On Saturday, a dry start to the day will give way to a band of
light to moderate showers along and ahead of a cold frontal
passage. The showers will be aided by a weak surface wave lifting
northeast along the front, plus upper divergence in the RRQ of a
110 kt jet streak and weak short-wave energy. There is a general
consensus for a narrow ribbon of weak instability (SBCAPE 200-400
j/kg) developing over the Fox Valley and lakeshore areas in the
afternoon, so have kept a mention of a few thunderstorms there.
Showers should arrive in NC/C WI mid to late morning, and Fox
Valley/lakeshore early to mid afternoon. High temperatures will
range from the upper 50s and lower 60s west and near Lake
Michigan, to 65 to 70 across inland areas of NE/EC WI.

Long Term...Saturday Night Through Friday

Saturday evening/night...Rain and a few thunderstorms will be
ongoing across far eastern WI into Saturday evening as a cold front
and mid-level shortwave tracks over the area. Not anticipating for
these storms to be strong or severe as the couple hundred J/kg of
instability over the area during the afternoon will rapidly decrease
into the evening. The showers and storms will exit the state by 06z
Sunday.

Sunday through Monday...High pressure and upper-level ridging moves
over the area during this time period, leaving dry weather and
mostly sunny skies across the forecast area. Temperatures will rise
above normal for both days with highs ranging from the mid 60s to
low 70s inland, and upper 50s to low 60s along the lakeshore.
Slightly elevated fire weather conditions are possible on Monday as
afternoon RH values will be in the 30s and southeast winds may gust
to 20 to 25 mph. Locations across the north would be of greatest
concern where green up has not fully occurred.

Rest of the extended...Models are still in agreement with an upper-
level trough developing over the Northern Plains Monday into
Tuesday. This will leave the forecast area in the southerly flow
ahead of the trough, allowing southern stream energy and moisture to
increase and lift into the Middle and Upper Mississippi Valleys.
Although there are still some timing and placement differences,
especially when the precip will end, Tuesday into Tuesday evening
appears to be the best timing for widespread rain and embedded
thunderstorms. Despite being in the warm sector, the timing of the
precip may hinder severe potential across the forecast area and keep
it confined south of the area. Will continue to monitor as there is
still plenty of time for the details to be ironed out over the
coming days. Details for the remainder of the extended become very
messy, but models agree with additional chances for precip at times
through the rest of next work week.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 612 PM CDT Fri May 3 2024

Expect VFR conditions to prevail through midday Saturday, with
patchy mid/high clouds expected into early Saturday. Thickening
and lowering clouds are expected in NC/C WI as showers arrive
toward midday and C/NE WI Saturday afternoon. Conditions will
deteriorate to MVFR Saturday afternoon as the showers arrive.
Considered the possibility of patchy fog tonight, but the air mass
was well mixed this afternoon (warm temps and low dew points
leading to large dew point depressions) and boundary layer winds
will be increasing to 20 to 25 kts late tonight. Models are
hinting at some low clouds coming off Lake Michigan (near MTW)
Saturday morning, but confidence is too low to mention a ceiling
at this time.

Gusty west winds will drop off quickly this evening, become light
SE overnight, then moderate SE-S later Saturday morning and SW
Saturday afternoon.

&&

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

&&

$$

DISCUSSION.....Kieckbusch/Kruk
AVIATION.......Kurimski