Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 121115
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
615 AM CDT Tue Mar 12 2024

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Elevated fire weather conditions are expected today.

- Near record of record high temperatures are possible at several
  locations today, with highs reaching into the 60s to lower 70s.

- Precipitation chances return Thursday through Friday morning,
  but uncertainty remains with how far north the precipitation
  will lift. Precip to start as rain, then transition to a mix of
  rain and snow or all snow Thursday night. Probability for 1 inch
  or more of snow is around 15-30% for much of the area.

&&

.DISCUSSION...
Issued at 310 AM CDT Tue Mar 12 2024

Short Term...Today...Tonight...and Wednesday

Near record warm temperatures and elevated fire weather conditions
are expected today as a cold front slowly moves through the
western Great Lakes region. Despite the passage of the cold front,
moisture will be very limited with the cold front; therefore,
precipitation is not expected as the cold front moves through the
region today. The cold front will instead be marked by a shift in
surface winds from southwest to west then northwest. Highs today
are mainly expected to be in the 60s, with some 70 degree values
possible across central Wisconsin and the Fox Valley.

Despite mostly clear skies behind a departing cold front tonight,
there will not be a push of especially cold air behind the front.
This will keep lows tonight rather warm, with temperatures closer
to climatological highs for the day. Lows tonight are only
expected to fall into the upper 20s across the north, with middle
30s across central and east-central Wisconsin.

A warm front will slowly be lifting north during the day on
Wednesday, although the area will still be on the "cold" side of
this feature. Despite being north of a warm front temperatures
will still rise into the 50s across the north, with highs in the
lower 60s across central Wisconsin as 850 mb temperatures remain
in the single digits above zero with a dry airmass in place and a
well mixed boundary layer.

Long Term...Wednesday Night Through Monday

A shift to a cooler and more wet pattern is expected for the end
of the week and through the weekend as two systems passing through
the region bring changes for rain and snow.

Precipitation...An upper-level closed low developing over the
Four Corners region and ridging building over the eastern Great
Lakes creating mean southwesterly flow through which a surface
low will propagate Thursday and Friday bring a chance for rain and
snow to the region. Ensemble guidances is in agreement that as
this surface low pushes into the central Plains Thursday it will
create a baroclinic zone across central WI, north of a warm front
stalling out across N IL/S WI. This set up will likely create a
band of frontogenetic forcing across central and east-central
which will drive much of the precipitation with this system.
However, exactly how far north this f-gen band sets up is still
unclear as the GEFS and ENS have it setting up across the Fox
Valley, while the GEPS takes it further north into Central WI. For
timing current guidance has precipitation beginning early
Thursday morning across central WI and spreading east and north
through the morning, however, thermal profiles are showing a
rather dry surface layer which may delay the onset of
precipitation. The heaviest precipitation is expected Thursday
afternoon/evening before diminishing Friday morning. Expect p-type
with this system to start as all rain, but with evaporative and
diurnal cooling a transitions to snow will be possible across
central and northern WI Thursday night into Friday. Probabilistic
guidance gives those regions about a 15-30% for greater than 1" of
snow by Friday morning. Lastly, there is a small chance (10-15%)
for some thunder Thursday afternoon/evening across the Fox Valley
where MUCAPE values are forecast to reach 200-400 J/kg and mid-
level lapse rates steepen near 7 C/km, however, surface dew points
will likely remain in the upper 30s with the better chance for
severe weather resides south of the aforementioned warm front
where dew points will be 10-20 degrees higher.

The second system forecast to impact Wisconsin comes Saturday
through next Monday as a low pressure system dives south out of
central Canada. With colder temperatures expected to be in place
this weekend this system carries a better chance (20-40%) for a
greater than 1" of snow, highest across northern WI. However, the
timing of the precipitation will be key in determining what areas
see more rain or snow.

Temperatures...With increased cloud cover and winds veering
northeast temperatues will trend cooler Thursday through Saturday
with highs in the mid 40s to around 50s and lows mid 20s to mid
30s each day. A cold front forecast to pass through Sunday will
usher in more seasonal temperatures Sunday and Monday with highs
dropping into the low 30s to low 40s and lows falling into the mid
teens to mid 20s.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 614 AM CDT Tue Mar 12 2024

VFR conditions are expected through the TAF period at the TAF
sites. Some fog is possible closer to Lake Michigan and the bay
early this morning, mainly north of Sturgeon Bay. Otherwise, high
clouds will continue to spread across the region at times
today. Light surface winds are expected this morning, with LLWS
expected as winds around 2000 ft gust to between 35-40 kts.
Southwest winds will shift to the west, then northwest later today
as a weak cold front pushes across the area. Surface winds will gust
to 15-25 kts from mid-late morning into the early-mid afternoon.
Lighter surface winds will return tonight.

&&

.FIRE WEATHER...
Issued at 310 AM CDT Tue Mar 12 2024

Warm temperatures will continue today, with compressional heating
along a weak cold frontal helping to boost readings into the
middle 60s to lower 70s. Deeper mixing near the front will also
boost winds, with SW-W winds gusting to 20 to 25 mph ahead of the
front, then turning NW as the front passes through NC/C WI. Dew
points and relative humidities will drop off again in the sand
areas, with RHs dropping to around 20 percent. After coordination
with the Wisconsin Department of Natural Resources and surrounding
offices, will continue with a Special Weather Statement for
elevated fire weather conditions over NC/NE/C WI through this
afternoon.

Dry weather will continue on Wednesday; although conditions will
be less critical than today. Temperatures will be cooler, ranging
from the middle 50s to lower 60s, along with RH values of 25 to
35 percent, and wind speeds of 5 to 10 mph.

&&

.CLIMATE...
Issued at 310 AM CDT Tue Mar 12 2024

Record or near record warmth is expected today. A list of record
highs for March 12: Antigo 65/1990, Appleton 72/1990, Green Bay
70/1990, Manitowoc 59/2006, Marshfield 68/2016, Merrill 68/2016,
Oshkosh 72/1990, Rhinelander 68/2016, Stevens Point 69/2016,
Sturgeon Bay 64/2016, Wausau 69/2016 and Wisconsin Rapids 70/2016.

&&

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

&&

$$

DISCUSSION.....Kurimski/GK
AVIATION.......Kurimski
FIRE WEATHER...Kurimski
CLIMATE........Kurimski


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