269
FXUS63 KGRB 272020
AFDGRB

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

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Southwest winds could gust to 45 mph or more across central and
  east-central Wisconsin this afternoon.

- It remains possible that conditions will support a few strong to
  severe storms late this afternoon into this evening across
  northeast Wisconsin, with the greatest risk of severe storms
  through 9 pm from the Fox Valley to the lakeshore. There is
  still a lot of uncertainty in the coverage of strong or severe
  storms.

- Better chances for rain return Sunday morning and continue
  through Monday. Periods of moderate to heavy rain Sunday 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 18Z TAF Issuance
Issued at 1230 PM CDT Sat Apr 27 2024

Windy conditions will continue at the TAF sites this afternoon
with southwest winds gusting to 30 to 40 knots at times. Winds
will slowly ease this evening below 20 knots then increase again
late tonight into Sunday morning as they turn to the northeast and
gust to around 20 knots.

Isolated showers and storms may redevelop after 22z, mainly south
and southeast of GRB and ATW as a cold front moves through the
area. After these showers and storms end this evening, most of the
night should stay mainly dry.

Ceilings will be IFR near the Lake Michigan shore, although
satellite imagery shows the low stratus is dissipating from south
to north. MVFR ceilings are expected across north-central
Wisconsin with VFR across most of central and east-central
Wisconsin. Other than RHI, most sites will be VFR this evening
then trend towards MVFR late tonight into Sunday morning. Another
low pressure system will bring steady rain to the area late
tonight into Sunday morning and last through Sunday night.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 4 PM CDT this afternoon for WIZ030-031-
035>040-045-048>050.
&&

$$

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