664
FXUS63 KGRB 281800
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1200 PM CST Fri Feb 28 2025

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Strong and gusty northwest to north winds are expected late this
  morning through this evening. The strongest winds with gusts
  over 45 mph will occur south of highway 29 and also across Door
  County. A Wind Advisory has been issued for portions of the
  area.

- Occasional light snow with 1 to 2 inches of accumulation will
  occur through this evening near the Upper Michigan border and
  over far northern Door County. Roads may become snow covered and
  slippery. The snow may mix with rain during the day.
  Temperatures falling below freezing late this afternoon and
  this evening could lead to icy spots on untreated roads where
  any precipitation occurs earlier in the day.

- Above normal temperatures today and again early next week could
  could lead to some break up of river ice, which will increase
  the threat for ice jams on area rivers.

- Travel impacts will be possible during the Tuesday night through
  Wednesday afternoon time frame of next week due to rain and
  wintry mix or accumulation snow over parts of the region. Those
  with travel plans during this time are advised to monitor
  future forecasts.

&&

.DISCUSSION...
Issued at 249 AM CST Fri Feb 28 2025

Short Term...Today...Tonight...and Saturday

Synopsis: A deepening low pressure system will track east-
southeast through the northern Great Lakes region today. This
system will bring a cold front through the area late this morning
through the afternoon and colder temperatures to the region
tonight. High pressure will then build in across the upper
Mississippi Valley on Saturday.

Winds: Winds will increase across the region this morning as the
pressure gradient tightens with southerly winds turning southwest
this morning, westerly by midday, then northwest this afternoon as
a cold front sweeps through Wisconsin. Winds will then turn
north-northwest tonight as the low pushes off to the east. Winds
are expected to gust to 45 to 50 mph at times along and south of
the highway 29 corridor as well as the lakeshore counties late
this morning into the early evening hours as winds at the top of
the boundary layer increase to 50 to 55 knots. The current timing
of the Wind Advisory look solid; however, southern portions of
Marathon and Shawano counties look like they will be close to Wind
Advisory criteria. Therefore, will expand the advisory to include
these counties. Wind speeds will drop off this evening and ease
further through out the day on Saturday as they turn back to the
northwest.

Snow: The best moisture and lift from this system will be across
the Michigan Upper Peninsula, where the highest snowfall amounts
are expected today. The rest of the region will likely see some
light snow or flurries along and behind the front, with some rain
possible ahead of the front where surface temperatures will be
substantially warmer. Snow will then continue tonight across far
north-central Wisconsin as winds turn north-northwest with a feed
of moisture from Lake Superior. Any snow will taper off Saturday
morning across the north as winds back more northwesterly.
Snowfall accumulations should be limited to an inch or two across
the far north close to the Michigan border, with less than an inch
elsewhere. Snowfall accumulations could reach 2 to 4 inches across
the lake effect snowbelt region of Vilas County through Saturday
morning.

Snow Squalls: Mesoscale models are indicating there is some
potential for snow squalls with the cold front tracking through
the region this afternoon as snow squall parameters rise along the
front, along with modest SBCAPE values around 50 J/kg, gusty winds
behind the cold front, and the potential for a flash freeze as
temperatures fall behind the cold front. The strongest signal for
this appears to be east- central and northeast Wisconsin to the
lakeshore as the front moves through during peak afternoon heating
and where the Snow Squall Parameter is maximized. However,
mesoscale models develop convective showers that are more
orthogonal to the snow squall parameter and cold front, along with
several striations of showers rather than parallel to the cold
front and push of wind and a more singular linear line of
convection. Therefore, confidence in a snow squall developing
isn`t high, but it isn`t zero either. Even if a snow squall
doesn`t develop, there will likely be brief reductions in
visibilities due to the convective nature of any snow showers that
develop, the gusty surface winds, and the potential for a flash
freeze as temperatures plummet behind the cold front.

Temperatures: Temperatures will rise to around 40 across the north
today with highs in the upper 40s across the Fox Valley ahead of
an approaching cold front. Temperatures will then tumble across
the region behind the cold front later this afternoon into this
evening. Some clearing skies and cold air advection will cause
temperatures tonight to plummet into the single digits across the
north, with lows of 10 to 15 across the Fox Valley and lakeshore.
Temperatures will recover some on Saturday to around 20 across the
north, with upper 20s across the Fox Valley.

Long Term...Saturday Night Through Thursday

High pressure will slide eastward across the area Saturday night,
resulting in the coldest night of the forecast period. Per latest
guidance and expected ridge location, lowered minimum temperatures
in our typical cold spots across the north due to the mostly clear
skies and light winds expected. Being early March, temperatures
will rebound nicely on Sunday with highs in the 30s. Tranquil
conditions should prevail Sunday night as the next feature
approaches the area from the west. A weak 500mb trough is expected
to move across the area Monday into Monday night. This feature
will bring a chance of rain or snow. Something to watch is on
Monday night, the models are depicting a west to east band of
precipitation. Latest forecast has this trend of high
precipitation chances across the north, but models have differing
solutions where this will set up.

The main system for next week is a little slower to arrive. The
main precipitation with this system is expected to arrive Tuesday
night with the heaviest precipitation falling overnight into
early Wednesday afternoon. Temperatures at the surface to 850mb
will play a big factor in precipitation types across northeast
Wisconsin. Could be rain/wintry mix and accumulating snow across
the area. The GFS/Canadian model were in better agreement with the
track of the system and heavier precipitation making it into
northeast Wisconsin. The ECMWF was weaker and further south with
the low with not a lot of precipitation across our eastern
counties. There are a lot of phasing issues with northern stream
system and the southern stream system that will have a large
impact the strength of the surface low and amount of precipitation
making it into northeast Wisconsin. Tranquil conditions are in the
forecast for Thursday. With the higher sun angle and temperatures
climbing above freezing early to middle of next week, the risk for
ice jams will continue.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1141 AM CST Fri Feb 28 2025

A short-wave trough and associated cold front will sweep through
the area this afternoon, accompanied by strong northwest winds
gusting to 30 to 40 kts and SCT-NMRS rain showers changing to snow
showers. A secondary short-wave will pass through during the late
evening and early overnight hours, but is not expected to produce
any significant precipitation. The exception will be over north
central WI, where conditions will be favorable for lake-effect
snow showers and some accumulation from late afternoon through
Saturday morning. Outside of the lake-effect areas, at least
partial clearing is anticipated after the passage of the second
short-wave late tonight.

The best chance of MVFR ceilings and local IFR vsbys will occur
over NC WI, with the worst conditions occurring due to lake-effect
snow shower in Vilas and northern Oneida counties, and possibly
northern Door County.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 3 PM this afternoon to 9 PM CST this evening
for WIZ022.

Wind Advisory until 6 PM CST this evening for WIZ030-031-035>040-
045-048>050.
&&

$$

DISCUSSION.....Kurimski/Eckberg
AVIATION.......Kieckbusch