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000
FXUS63 KGRB 181821
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
121 PM CDT Thu Apr 18 2024

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Showers return to the area today, with the best chances south of
  Highway 29.

- Friday is expected to be windy with westerly winds gusting to 30
  to 40 mph, especially across central and east-central
  Wisconsin.

&&

.DISCUSSION...
Issued at 356 AM CDT Thu Apr 18 2024

Short Term...Today...Tonight...and Friday

A low pressure system over the southern Plains will track
northeast towards central Illinois today. As the low moves south
of the area, some mid level frontogenesis will combine with a
100-120 knot upper level jet to bring showers to the region
throughout the day. The best chance (40-60 percent) will be south
of highway 29 with the best moisture and dynamics, with lower
chances (20-40 percent) further north. Instability and lapse rates
will be too low for thunderstorms, with only rain showers expected
from this system. Highs today are expected to mainly be in the
middle to upper 50s.

The rain showers will end from west to east this evening as the
low tracks northeast towards southern Ontario tonight, with dry
weather expected during the overnight hours. Low temperatures
tonight are expected to range from around 30 across the north, to
the middle 30s across east-central Wisconsin.

A vigorous mid level shortwave will track through northern
Wisconsin during the day on Friday, which will bring the chance
(20-30 percent) for light snow to north-central Wisconsin late
Friday morning through the afternoon. Despite the light snow
showers, snowfall amounts will be de minimis on Friday as the sun
being up will limit accumulations, especially on pavement. A tight
pressure gradient and deep boundary layer to 700-750 mb will
bring gusty winds back to the region, with westerly winds expected
to gust to 30 to 40 mph at times. Highs on Friday are expected to
range from the lower 40s across the north, to the lower 50s
across east- central Wisconsin.

Long Term...Friday Night Through Wednesday

Precipitation...An upper-level low will shift northeast over James
Bay Friday night into Saturday morning, leaving the trailing
shortwave/trough overhead. This will allow low-level/surface winds
to turn the favorable northwest direction for lake-enhanced precip
in far northern WI. Forecast soundings do not show as deep of low-
level saturation as previous runs during this time, but there still
appears to be enough to combine with shortwave trough energy
overhead to generate light snow showers or flurries along the
WI/Upper MI border. High pressure will build into the region for the
remainder of the weekend bringing the return of dry and sunny
conditions. As the high pressure departs on Monday, it will make way
for the next chance for precip from a low pressure system
originating from the Plains. There are still timing and placement
differences with this system as it will have to overcome dry air
from the departing high. But, a general consensus has precip
residing over the area from Monday night through Tuesday evening.
Warmer air will be in place at the start resulting in rain, but a
switch to a rain/snow mix may be possible on Tuesday, especially
across the north, as the system is departing the region. High
pressure will shift over the region following this system for
midweek.

Temperatures...Lingering cool air will keep temperatures about 5 to
10 degrees below normal on Saturday (highs ranging from the middle
40s to low 50s). A warming trend follows for Sunday and Monday, as
weak ridging builds into the region. Sunday`s highs will be slightly
above normal ranging from the middle 50s to low 60s, while Monday`s
highs will be about 5 to 10 degrees above normal ranging from the
upper 50s to middle 60s. Temperatures will take a dip below normal
again on Tuesday and Wednesday due to the anticipated precip and
trailing cooler air.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 121 PM CDT Thu Apr 18 2024

VFR conditions will gradually give way to MVFR conditions this
afternoon as a weak low pressure system brings scattered light
rain showers across central and eastern WI. Conditions should
then improve back to VFR this evening as the rain exits the area
to the east and drier air advects into the region. Clouds and a
few snow showers will build into northern WI on Friday. Conditions
should remain VFR. Otherwise, expect just scattered mid clouds
across the area.

W/WSW winds are expected this afternoon with gusts up to 20 knots.
Winds will ease below 10 knots this evening, before becoming 10-15
knots overnight. On Friday, west winds will increase to 15-20 kts
with gusts to around 30 knots. The strongest wind gusts will impact
the central to east-central WI terminals.

&&

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

&&

$$

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