573
FXUS63 KGRB 200437
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1137 PM CDT Wed Mar 19 2025

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- A potent spring storm will impact the region through late
  tonight, bringing heavy snow to central, north- central, and far
  northeast WI, and rain changing to sleet and snow elsewhere this
  evening. A few thunderstorms are also possible late this
  afternoon and evening in the Fox Valley and central WI. Winter
  Storm Warnings and Winter Weather Advisories have been issued
  across most of the forecast area.

- Strong northeast to north winds gusting to 30 to 45 mph may
  produce pockets of blowing snow in open areas through tonight.
  The combination of wet, heavy snow and strong winds could cause
  tree damage and produce sporadic power outages as well.
  Hazardous travel conditions are expected region-wide.

- A prolonged period of snow mixed with rain at times is expected
  Sunday into Monday. At this time, there is a 40 to 70% chance of
  3 inches of snow from Sunday and Sunday night across the entire
  area, and a 30 to 50% chance of 6 inches across the north.

&&

.DISCUSSION...
Issued at 348 PM CDT Wed Mar 19 2025

Short Term...Tonight and Thursday

Water vapor imagery shows a strong low pressure system moving across
northern Missouri this afternoon creating widespread areas of snow,
sleet, and rain across the upper Midwest. Regional radar and RAP
analysis shows a band of heavy snow developing due to an area of
strong mid-level frontogenesis extending from northern Iowa into
central WI. Within this band of 1-hr snow rates are likely 1-2" per
hour which is in like with the 12Z HREF. As the stronger forcing
moves northeast expected those higher snowfall rates to develop from
central to far northeast WI, where a Winter Storm Warning is in
effect. RAP analysis also shows increase mid-level instability across
central WI leading to some convectively enhances snow in those
regions. Overall snowfall amounts remain highest (4-8")along a line
from AUW to ESC. The biggest question for the remainder of the
afternoon is when will rain transition to snow in the Fox Valley
and along the lakeshore. With temperatures still the mid 30s in the
Fox Valley it may take another hour or two to cool enough for the
transition to occur. For areas in the Fox Vally and along the
lakeshore snow accumulations are expected to reach 3-6" with locally
higher amount possible in Door Co. Area web-cams show snow has also
been slow to accumulations roads, however, once the sun begins to
set may see a rapid deterioration in road conditions this evening.
There is going to a sharp cut off in snow amounts across north-
central WI as drier air is winning our north and west of an RRL to
LNL line.

Winds are also starting to increase across the region this afternoon
with gusts pushing 30-40 mph. Northerly winds across the region will
continue to increase late this afternoon evening. Blowing snow may
cause sporadic reductions in visibility across the open areas of
central WI this evening. Sporadic power outages and tree damage are
also possible and winds increase and wet snow accumulations are
trees and powerlines.

Snow is expected to come to an end from west to east overnight with
most of the region expected to turn dry by day break Thursday.
Breezy west winds will linger through Thursday morning before
starting to diminish during the afternoon.

Long Term...Thursday Night Through Wednesday

Tranquil conditions will prevail Thursday night into Friday
morning as a cold front approaches from the northwest. As
the front moves into the area, this feature will bring a chance
of light rain during the afternoon and evening. The rain could
end as light snow as temperatures fall during the evening.

The main system of concern is a prolonged period of light snow
mixed with rain at times Sunday into Monday. A 500mb trough is
expected to close off and become negatively tilted Sunday
afternoon into Monday. On Sunday, the GFS model indicated 145
knot jet streak passing south of the area, with much of the area
in the favorable left exit region of the jet which will enhance
lift across the area. Models did show weak 850mb warm advection
of the upper level disturbance that should move across the
area. Temperatures are expected to warm into the 30s, however
some large temperature/dewpoint spreads in the guidance would
suggest temperatures will fall back closer to freezing once the
precipitation arrives. Snowfall accumulations difficult to
determine this time of year due to higher sun angle, air and
ground temperatures above freezing. Snowfall rates will also be a
determining factor, especially during the day. Looking at the
DESI, probabilities of 3 inches of snow Sunday and Sunday night is
between 40-70%, highest chances across the north. There is a
30-50 of 6 inches across the north. The chances for mainly snow
will continue Monday as the upper low moves across the state. Will
need to watch to see if there are more significant snow shower
activity with this feature that could impact visibilities for
motorists.

The northwest flow pattern will continue Monday night
into Wednesday which results in low to medium confidence
in the dry conditions as the model have small features dropping
southeast into the central portion of the country during this
time frame. Seasonable temperatures will continue into the middle
of next week.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1136 PM CDT Wed Mar 19 2025

Snow will continue to come to an end from west to east overnight.
Conditions have improved to VFR where the snow has ended, with
MVFR/IFR conditions where snow is ongoing. Conditions will improve
to VFR overnight as the snow ends and drier air works into the
region. High pressure will then ensure VFR conditions prevail on
Thursday.

Surface winds will continue to be very gusty through Thursday
morning, with gusts of 20 to 30 knots at times from a northerly
direction. Winds will eventually back to a northwesterly direction
Thursday morning as they gust to 20 to 30 knots then back further
to a westerly direction Thursday afternoon with gusts around 20
knots. LLWS will continue into early Thursday morning as winds
just off the surface gust to 40-50 knots, then ease Thursday
morning as these winds subside. LLWS is possible again Thursday
evening across central and north-central Wisconsin as southwest
winds just off the surface gust to around 35 knots with a light
surface wind.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 1 AM CDT Thursday for WIZ020-021-031-
035-036-073.

Winter Storm Warning until 7 AM CDT Thursday for WIZ022.

Winter Weather Advisory until 1 AM CDT Thursday for WIZ038-048.

Winter Weather Advisory until 7 AM CDT Thursday for WIZ039-040-
049-050.
&&

$$

DISCUSSION.....GK/Eckberg
AVIATION.......Kurimski

NWS GRB Office Area Forecast Discussion