596
FXUS63 KGRB 272346
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
646 PM CDT Sat Apr 27 2024

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...


- There is a good chance for rain Sunday through Monday. Periods
  of moderate to heavy rain Sunday afternoon into Monday morning,
  could result in isolated flash flooding in urban and low lying
  areas. Rivers will be on the rise through the middle of next
  week, with a few of them reaching bankfull stage.

- Conditions hazardous to small craft are expected this weekend on
  the Bay and Lake. A few gale force gusts are possible this
  afternoon, especially on the southern end of the bay and Lake
  Michigan south of Manitowoc.

&&

.DISCUSSION...
Issued at 319 PM CDT Sat Apr 27 2024

Short Term...Tonight and Sunday

Gusty southwest winds will continue ahead of an approaching cold
front slated to track through the region late this afternoon into
early this evening. Despite the passage of this cold front,
precipitation chances will remain low for east-central Wisconsin
as model soundings show a substantial mid-level capping inversion
in place around 750 mb with abundant dry air. Although some
showers and thunderstorms could develop in the far southeast
corner of the cwa in Manitowoc or Calumet counties, hi-res models
keep most of the activity to the southeast or only in these
counties for a brief period of time. Therefore, will only keep a
small chance for convection late this afternoon and early this
evening (20-30 percent) before the cold front tracks through the
area.

Any convection that can develop will have the potential to be
severe given the SBCAPE values of 1000-1400 J/kg and bulk shear
values of 40 to 45 knots; however, hodographs show that despite
decent veering of direction and speed in the lowest 3 km, there is
backing between 3 to 6 km, which would act to inhibit updraft
development as dry air gets entrained within the storm. Therefore,
confidence in seeing severe weather even across the southeastern
portion of the cwa is rather low despite the decent parameters.

A low pressure system lifting north towards Iowa on Sunday will
bring a swath of rain showers and embedded elevated thunderstorms
late tonight from the southwest and spread across the rest of the
area during the day on Sunday. Cool northeast winds on Sunday will
make for a fairly cool day when combined with the persistent rain
showers expected.

Long Term...Sunday Night Through Saturday

Precipitation...Rain showers and a few embedded thunderstorms will
be ongoing at the start of this forecast period for Sunday night as
a warm front gradually lifts north across the state, paired with an
increasing low-level jet. Although there are timing differences in
the placement and timing of the warm front (some guidance delays the
front lifting north till Monday morning), there is still decent
agreement with the forecast area seeing an increase in rainfall
between Sunday night and Monday morning. PWATs during this time will
be between 1 and 1.40 inches, leaving the potential for localized
heavy rainfall, leading to possible flash flooding, especially in
urban areas. A few elevated thunderstorms are possible throughout
Sunday night into Monday morning, however, the potential for severe
storms looks low given the uncertainty in the timing and placement
of the warm front. Precip will decrease in intensity for the
remainder of Monday, as the warm front`s surface low tracks
northeast across the state. The precip should come to an end Monday
evening/night.

Surface ridging will build over the area for Tuesday, resulting in
dry conditions. A quick-moving shortwave and surface cold front will
bring the next chance for precip Tuesday night, and exit by
Wednesday afternoon. A few elevated thunderstorms are possible, but
given the timing of the precip, the potential for severe storms is
low at this time.

Details for the remainder of the forecast period are unclear, but
there appears to be some agreement with a prolonged period of precip
chances to end the week and continue for a portion of the weekend.

Temperatures...With a warm front expected to lift over the region on
Monday, normal or above normal highs are anticipated ranging from
the mid to upper 50s in north-central WI to the mid to upper 60s in
east-central WI. The warm air will stick around for Tuesday,
allowing all locations to warm above normal with readings ranging
from the mid 60s to low 70s. Due to the timing of the cold front
occurring Tuesday night, temperatures should be able to rebound
quickly enough on Wednesday to remain above normal. With potential
for rainfall for the remainder of the extended, temperatures will
take a dip back to closer to normal.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 644 PM CDT Sat Apr 27 2024

A cold front will move across the area tonight and stall across
southern Wisconsin towards daybreak Sunday. A low pressure system
will move northeast along the front and bring showers and isolated
thunderstorms Sunday and Sunday night.

Mostly MVFR ceilings are expected this evening west of a IMT to
ISW withe VFR to the east. Ceilings will become MVFR/IFR across
most of the region Sunday and Sunday night.

&&

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

&&

$$

DISCUSSION.....Kurimski/Kruk
AVIATION.......RDM