288
FXUS63 KGRB 212351
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
651 PM CDT Fri Mar 21 2025

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- A brief period of rain changing to snow will occur across the
  region during this evening. Southwest winds gusting to 25 to 35
  mph will become NW-N this evening. Minor snow accumulations of
  less than an inch are possible in far northern and northeast
  WI.

- Snow, mixed with rain or freezing rain at times Saturday night
  into Sunday morning, is expected late Saturday night into
  Monday. The greatest probability for 6+" of snow remains highest
  across the Northwoods (40-50%) with the potential for a sharp
  cut off in amounts further south.

&&

.DISCUSSION...
Issued at 336 PM CDT Fri Mar 21 2025

Rain to snow as cold front crosses...
Sharp mid-level trough with 12hr height falls up to 80m digs
across western Great Lakes tonight. Surface low over central Upper
Michigan slides east, dragging a cold front across WI tonight. Thus
far, dry air has restricted development of precipitation upstream.
Eventually there will be enough saturation for a brief period
(2-3 hr) of rain changing to snow especially northeast to east-
central WI. Northwest winds in wake of the front will become gusty
into the overnight hours. Gusts to 30 mph are expected from 9p to
2a, strongest from central to east-central Wisconsin. Temperatures
will fall into the upper single digits to lower teens by late
tonight over northern Wisconsin, and in the 20s elsewhere. Where
precip occurs this evening, the below freezing temps could lead to
slippery spots.

Late weekend system with snow/freezing rain and rain...
Shortwave trough digging across Pacific Northwest this afternoon
reaches the central Plains late Saturday afternoon. Trough becomes
negatively tilted Saturday night into Sunday as strong upper jet
digs over the northern Plains. Associated surface low over the
plains on Saturday becomes more closed off and slightly deepens
by time it crosses northern WI on Sunday. Surge of gulf moisture
boosting PWATs to near 0.70 inch/90th percentile within 50+ kt
low-level jet supports initial swath of warm air advection precip
late Saturday night into Sunday morning. Soundings and NBM ensemble
ptypes support mainly snow north and east, but a wintry mix of
freezing rain and snow into central WI. Then as the primary trough
axis arrives on Sunday morning, expect expansion of next shield of
precip west to east. QPF has increased with this second round of
precip which will likely remain mostly snow north and a wintry mix
changing to rain south of Highway 8.

This looks like a solid advisory event due to wintry mix and/or
snow. Probabilities for 6 inches or more of snow from late
Saturday night through Sunday night did decrease slightly on the
NBM (40-50% latest compared to 50-60 percent previously), but
still are generally located in the same area, over northern WI
from Langlade County to Florence and Marinette counties. Given
that trend and after coordinating with NWS MQT, did not issue a
Winter Storm Watch at this time. A further consideration is that
when most of the heaviest snow is expected over the north,
snowfall rates will be less than 1"/hr and it will be during the
daytime. Thus, absent higher snow rates, impacts on roads may be
lower than if this system occurred earlier in the winter when sun
angle is lower.

Outlook for next week...
Beyond the late weekend system it looks quiet. Temperatures slightly
below normal to start the week will rise above normal by Wednesday
and through the rest of the week.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 650 PM CDT Fri Mar 21 2025

Mainly VFR conditions are expected as a cold front drops south
through the area this evening and high pressure slides into the
region on Saturday. The cold front will bring a 2-3 hour chance of
some rain switching to snow. Lingering flurries are possible
across far northern and eastern WI overnight as some lake effect
activity picks up. Patchy MVFR conditions are possible along and
behind the front. Saturday will feature low VFR (or possibly high
MVFR) ceilings in the morning across north-central to along the
Lake Michigan shore. Clouds will scatter out through the morning,
leaving VFR conditions for the afternoon.

W/SW winds ahead of the front will continue to shift to the NW
behind the front. Some gusts to ~25 kts are expected, especially
behind the front and as the stronger cold air advection arrives.
Winds will decrease Saturday morning, then become variable under 6
kts in the afternoon as they shift from from the northwest to the
southeast by late afternoon.

&&

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

&&

$$

DISCUSSION.....JLA
AVIATION.......Bersch