541
FXUS63 KGRB 121206
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
606 AM CST Wed Feb 12 2025

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Accumulating snow is expected today and tonight. Snowfall will
  range from less than an inch in far north central WI to 3 to 5
  inches in the Fox Valley and lakeshore areas. Lake enhancement
  could boost totals to as high as 7 inches in Manitowoc County.
  Hazardous travel conditions can be expected, especially during
  the evening commute.

- There is a 70-90% chance of greater than 3 inches of snow
  Friday afternoon into Saturday morning. Hazardous winter travel
  is expected across most of the area.

- Cold wind chills from 5 below to 25 below zero are possible
  Thursday morning, Friday morning and Sunday morning. Bitterly
  cold wind chills of 20 below to 35 below zero are possible
  Monday morning and Tuesday morning. The coldest wind chills
  will be found over central and north-central Wisconsin each
  morning.

&&

.DISCUSSION...
Issued at 337 AM CST Wed Feb 12 2025

Short Term...Today...Tonight...and Thursday

No changes were made to the winter weather headlines.

Mid-level clouds covered most of the forecast area early this
morning, with the exception of Vilas County, where frigid
temperatures in the teens below zero were still being reported.
Light snow had developed over IA and northwest IL, where modest
lift was being generated by WAA, FGEN and weak short-wave energy.

Snow is expected to develop as low pressure in the southern
Mississippi Valley moves into eastern TN/KY today, then to western
Lake Erie tonight. A dry wedge around 850 mb will slow the steady
snow development until mid to late morning, so the morning
commute should be uneventful. Forcing will be supplied by
transient bands of low to mid-level frontogenesis, WAA and the RRQ
of a 130 knot jet. Much of this lift will occur above the DGZ
early in the event, but more favorable conditions will set up over
the southeast CWA during the late afternoon and evening, during
the evening commute. Not expecting a big contribution from lake-
enhancement early in the event due to weak low-level winds and
abundant shear. However, a more favorable period of unidirectional
ENE-NE flow will support lake-enhancement during the late
afternoon and evening. This enhancement will wane as winds turn
N-NNW overnight. Most of the accumulation will occur by midnight,
but light snow or flurries will persist overnight, and possibly
through Thursday morning, as a final short-wave trough moves
through. Total accumulation of powdery snow will range from less
than an inch over far NC WI to 3 to 5 inches over most of the Fox
Valley and lakeshore areas. Locally higher amounts up to 7 inches
are possible in Manitowoc County due to lake-enhancement. Current
snowfall totals match nicely with the ongoing advisory/warning
headlines, so will stay the course. Have to admit that it is a bit
disconcerting to still have dew points in the single digits and
teens below zero over the entire region only six hours before snow
is supposed to arrive. That being said, a slightly slower arrival
time or slightly lower totals would not be a big surprise.

High temperatures should reach the teens and lower 20s today, and
upper single digits and teens on Thursday. Lows tonight should
range from a few degrees below zero west to around 10 above east.
Wind chills as cold as 15 to 20 below zero are possible in north
central and central WI early Thursday morning.

Long Term...Thursday Night Through Tuesday

The main concern for this period will be the expected accumulating
snowfall Friday afternoon into Saturday morning, and then the
trend of below normal temperatures and bitterly cold wind chill
readings at times.

For Thursday night, skies are expected to become clear to partly
cloudy with light winds expected from late Thursday evening
through sunrise on Friday morning. This is a recipe for temps to
tank, especially in our typical cold spots. Have lowered minimum
by a few degrees at most places. The next weather maker approaches
from the west Friday morning. Only the GFS depicts snow breaking
out before noon Friday across north-central Wisconsin. Will leave
Friday morning dry with snow arriving across much of the area
Friday afternoon. Strong 850mb warm advection and increasing lift
in response to a 300mb jet streak should allow for snow to break
out. Snow is expected Friday night as the system moves across the
area. Probabilities for 3 inches of snow now stands at 70-90%.
There is a fairly high probability over 50% that snowfall amounts
could be over 6 inches in some spots. There is one thing to watch
is the GFS/ECMWF are bringing a secondary wave of low pressure
across the region late Friday night into Saturday morning,
resulting in another band of snow. The placement of this band
varies greatly, but the ECMWF model tonight would have the biggest
impact with additional accumulations of snow with this feature.
The GFS and Canadian model place this band to the south of the
area.

Fairly tranquil conditions are expected for the rest of the
period. Except for Saturday where high temperatures will be a
little closer to normal, well below normal temperatures are
expected at least through the middle of next week. Bitterly
cold wind chills 10 below to 25 below zero are expected
Friday morning, and then again Monday and Tuesday morning. Wind
chill readings down to around 30 below zero are possible Monday
morning across north-central and central Wisconsin. Looking
beyond the forecast, the 6-10 day and 8-14 day outlooks from the
Climate Prediction Center favor the probability of below normal
temperatures during these periods.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 544 AM CST Wed Feb 12 2025

VFR conditions will deteriorate to MVFR/IFR as light snow spreads
north across the region from mid-morning through early
afternoon. Light snow will continue in most areas into tonight,
but may become moderate at times in the Fox Valley and lakeshore
areas during the late afternoon/evening, with vsbys occasionally
dropping into the LIFR category. A general decrease in snow
intensity should occur from west to east overnight.

Plowing operations will be needed across much of the area,
especially in the Fox Valley/lakeshore areas, where 3 to 6 inches
of powdery snow can be expected by midnight tonight. Farther
northwest, amounts will drop off, with far north central WI
receiving an inch or less.

Light NE winds will become N-NW and a bit gusty tonight.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from noon today to 6 AM CST Thursday for
WIZ022-037>040-045-048-049.

Winter Storm Warning from noon today to 6 AM CST Thursday for
WIZ050.
&&

$$

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