612
FXUS63 KGRB 242317
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
517 PM CST Sun Nov 24 2024

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Rain and a wintry mix of snow, sleet and freezing rain arrive
  tonight. The precipitation type will remain rain tonight south
  of highway 64 (Merrill to Marinette). Rain will change to snow
  on Monday across central WI, but stay mainly rain over northeast
  and east-central Wisconsin.

- There is a 20-40 percent of seeing over 4 inches of snow by late
  Monday afternoon over north-central Wisconsin. A small area
  could see a hundredth or two of ice accumulations tonight.
  Slippery roads are likely north of a Rhinelander to Iron
  Mountain line. A Winter Weather Advisory has been issued for
  Florance, Forest, Oneida, and Vilas Counties.

- A cooling trend takes hold this week. Highs in the 30s and 40s
  into Monday will cool into the 20s to 30s by the middle of the
  week, and into the 20s across the entire area by next weekend.
  Subzero wind chills possible Friday night and Saturday night.

&&

.DISCUSSION...
Issued at 250 PM CST Sun Nov 24 2024

Short Term...Tonight and Monday

Surface observations and satellite imagery show a surface low
pressure system lifting northeast into western IA this afternoon.
Isentropic ascent ahead of this low will start to produce areas of
drizzle and light rain across central WI this evening as the low
continues to lift northeast toward the WI/IL border. As the
precipitation spreads further northward expect a transition to snow
tonight north of a Merrill to Marinette line. There may also be a
period of freezing rain along and north of this line as forecast
soundings show a weak warm noise.

Expect the heaviest periods of snow across northern WI overnight as
the strongest forcing associated with the low moves through this
region. There has been an uptick in forecast snow amounts from
previous forecast cycles due in part to a slight northward shift in
the low track as well as slightly cooler surface temperatures. Snow
totals are expected to range from 2-6 inches across northern WI by
noon Monday, highest amounts along the WI/UP border. NBM probs have
a 55-75% for greater than 2" north of a Rhinelander to Iron Mountain
line, and a 20-40% chance for greater than 4 inches north of this
line. A Winter Weather Advisory has been expected to include
Florance, Forest, Oneida, and Vilas Counties.

The transition to snow across central WI is not expected to happen
until Monday morning across central WI as a surge of colder air
aloft wraps around the backside of the low. Accumulations in central
WI are expected to be light with only a 10-20% chance for greater
than 1". East-central WI and far northeast WI may also see a few
snowflakes mix in Monday, but mainly rain is expected in these
locations.

Northwest winds will start to increase Monday afternoon behind the
low, but the snow coming to an end don`t expect much in the way of
blowing or drifting snow impacts.

Long Term...Monday Night Through Sunday

Despite an upcoming weather pattern change, widespread
precipitation is not expected from Tuesday onward as surface-
based low pressure exits our area and curves up into the Hudson
Bay region of Canada. This Hudson Bay low will then become
integrated into broader low pressure trough development over
eastern North America. The trough will drag upper-level
distubances down across our area at times for the remainder of the
week, but as of now only light preciptation is anticipated on the
northern and eastern fringes of northeast Wisconsin.

The bigger story for our region will be the first significant
arctic air intrusion of the season arriving later in the week, as
the broad troughing aloft over the eastern U.S. strengthens and
pulls Canadian air into the western Great Lakes. Temperatures will
be slightly below normal Tuesday through Thanksgiving, then drop
markedly from there...with highs on Saturday and Sunday struggling
to climb above the mid 20s even near Lake Michigan. Low
temperatures on Friday and Saturday night are expected to drop
into the single digits to low teens across our area, with wind
chills below zero possible.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 513 PM CST Sun Nov 24 2024

A surface low will push into the upper-Mississippi Valley this
evening, causing CIGs to fall to MVFR and eventually IFR/LIFR
overnight into Monday morning. Drizzle and light rain will also
start to spread northeast this evening beginning in central WI
around 00Z. As the low moves along the WI/IL border toward lower
MI overnight, precipitation will become more widespread with
mainly rain showers south of a Merrill to Marinette line and snow
north of this this line. The heaviest periods of snow are expected
between 06Z-12Z Monday morning across far northern WI.

As winds turn to the north Monday morning and cold air starts to
advance further south snow may start to mix in with the rain
across central WI. Greatest snowfall amounts of around 1-4 inches
are expected north of Rhinelander to Iron Mountain line. The low
will pull away from the region Monday afternoon, allowing CIGs to
improve to MVFR/IFR Monday afternoon as precipitation starts to
end from southwest to northeast.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 10 PM this evening to noon CST
Monday for WIZ005-010>012.
&&

$$

DISCUSSION.....GK/ML
AVIATION.......Kurimski