512
FXUS63 KGRB 092357
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
557 PM CST Sat Nov 9 2024

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Widespread light rain likely (70% to 90% chance) this evening
  into Sunday, with another round of rain likely (50% to 70%
  chance) Wednesday.

- Above-normal temperatures continue into at least next weekend.

&&

.DISCUSSION...
Issued at 310 PM CST Sat Nov 9 2024

Short Term...Tonight and Sunday

Main focus from this forecast period revolves around precip trends
associated with a low pressure system expected to track across the
Central Plains to WI through Sunday evening.

This afternoon`s water vapor imagery showed the vertically stacked
low pressure system over NE, while southerly flow ahead of the
system was lifting moisture across the Midwest. Meanwhile, regional
radar imagery showed a broken area of rain lifting across
southeastern MN, southwestern WI, and eastern IA. These
broken/scattered rain showers are expected to gradually lift into
the forecast area from southwest to northeast this evening and
overnight.

A break in the showers is possible Sunday morning as mid-level dry
air filters into the area ahead of the low. However, enough low-
level moisture will stick around to keep drizzle or mist ongoing
before the low pressure system arrives from the west early Sunday
afternoon. Rain showers are expected to accompany the low as it
tracks east across the state during the afternoon and evening. The
rain will end with the departure of the low Sunday evening. Cannot
rule out the low chance (up to 20%) for thunderstorms to occur
during the afternoon in central and east-central WI, as models
indicate mid-level lapse rates around 7C/km and weak elevated
instability (MUCAPE up to 200 J/kg).

Long Term...Sunday Night Through Saturday

Any lingering rain showers will end across northern/eastern WI
Sunday evening as the upper low/trough exits the region. A cold
front will cross the area on Monday, turning the flow to the
northwest. As temps cool, delta Ts will climb into the mid teens,
with favorable NW/NNW trajectories for a short time, creating the
chance for a few lake effect rain showers, mainly Monday morning.
A few flakes may mix in as the boundary layer cools, but no
accumulation is expected. Soundings support some drizzle at times
as well Sunday night into early Monday. The colder, cyclonic flow
will also help keep plenty of clouds in the area Sunday night into
Monday, with drier air slowly for clearing skies later Monday
into Monday night, especially in/toward central WI. A period of
gusty northwest winds is expected behind the front on Monday,
gusting to 35 mph. Surface high pressure and mid- upper level
ridging builds into the region Tuesday, bringing dry and quiet
conditions.

A quick moving trough will swing through the Great Lakes on
Wednesday, bringing the next round of showers. Limited moisture
and the quick nature of the system will limit rain amounts to
under a quarter inch. Dry conditions return Thursday and Friday as
high pressure builds in. Temperatures will run a little above
normal for most of the period, with only a brief shot of colder
air behind the front Monday night.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 544 PM CST Sat Nov 9 2024

Aside from lake-enhanced SCT-BKN MVFR stratocumulus over eastern
WI, mid-level clouds covered the region early this evening. A few
light showers/sprinkles were ongoing over C/NC WI.

Showers should become more numerous and ceilings gradually lower
later this evening and into the overnight hours, as WAA and
moisture convergence increases on the nose of 35 kt low-level jet.
This forcing will shift east late tonight, and an influx of drier
mid-level air will cause the showers to taper off to drizzle/fog
in most areas. As this occurs, flight conditions will deteriorate
to IFR/LIFR across most of the region. Another round of showers
will accompany the passage of a vertically stacked low pressure
system from late morning through mid to late afternoon. Modest
improvement in flight conditions will occur from west to east as
the rain ends later in the afternoon.

Southeast winds will prevail through Sunday morning, then turn
southwest to west as the low moves through in the afternoon.

&&

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

&&

$$

DISCUSSION.....Kruk/Bersch
AVIATION.......Kieckbusch