Area Forecast Discussion
Issued by NWS Green Bay, WI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43
000
FXUS63 KGRB 220806
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
306 AM CDT Fri Mar 22 2024

Forecast discussion for routine morning forecast issuance

.KEY MESSAGES...

-  Slow or difficult travel is expected for this morning`s
   commute, particularly over central and east-central Wisconsin
   due to a moderate snowfall. Road conditions will start
   improving by late morning as the snow tapers off.

 - Confidence continues to slowly increase for another strong
   system to provide snow accumulations from Sunday into Monday.
   There is a 50 to 90% chance of at least 4 inches of snow
   accumluations across areas northwest of the Fox Valley, but
   confidence is only medium with these percentages.

&&

.DISCUSSION...
Issued at 306 AM CDT Fri Mar 22 2024

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

Widespread snow is impacting the area this morning ahead of PV
anomaly/shortwave digging across the northern Plains. Since last
evening, northern FGEN band based at H7-H6 has been the more
active with persistent moderate snow from northeast of the Twin
Cities into central WI along and south of highway 29. SLRs have
been higher in this band and the snow has been quite fluffy and
efficient with radar estimates and sfc obs pointing to snowfall
rates of at least 1"/hr at times. Farther north, snow is much
lighter farther away from the sloped frontal sfc. Expect steady
snow to continue through 09z/4am all areas, then begin to ease
over the northwest forecast area as shortwave sliding through
helps to shove the primary FGEN band of concentrated snow farther
south.

Snow totals along and south of highway 29 by mid morning will
likely check in solidly in the 3-4" range while southern portions
of the area could end up more in the 4 to locally 6" range
depending on how long the northern edge of the FGEN band is
persistent. This snow in this band could be even further enhanced
as increasing mid-level lapse rates (upright instability) moving
into southern WI attm begin to interact with the band of snow.
Again, this will mainly be along and south of ISW/OSH/MTW into
13-14z/8-9am. Overall snow timing/trends/amounts on track thus far
so will not make any changes to the advisory. As we have been
pointing out a while, the commute this morning will be slow and
difficult. Give yourself extra time if heading out this morning.

By late morning into midday, steady snow will diminish all areas.
Secondary shortwave approaching and low-level trough dropping in
from Lake Superior/Upper Michigan could still spur on some light
snow mainly far northeast WI to the Upper Michigan border. As that
trough sharpens and drops across the area late today into this
evening, a flare up of light snow and flurries may expand over
northeast WI, including the Green Bay metro. Could see local snow
amounts up to an inch as this drops across. Snow ends after
midnight all areas and skies may clear out especially west and
north-central. Undercut guidance a bit there (lows in the lower
single digits) given fresh snow cover and clearing skies.

Saturday looks quiet with seasonably cool temps (highs centered
on mid 30s) and a mix of sun and clouds. We`ll catch our breath
before the next potentially high impact system with winter impacts
moves back in to close the weekend.

Long Term...Saturday Night Through Thursday

Focus in this part of the forecast remains on the potential for
significant winter weather in the Sunday to Monday timeframe on the
leading edge of a strong cyclone due to pass across the region early
next week.

Saturday night through Monday...The ensemble means are in good
agreement depicting a large western trough moving from the west
coast at the start of Saturday night to the Great Plains by Monday.
Backing and strengthening flow aloft will bring in light snowfall
into north-central Wisconsin as early as late Saturday night.  With
further increases in south flow aloft combined with upper divergence
and mid-level fgen, increasing forcing eventually brings in strong
lift and higher precip rates to central, north-central, and far
northeast WI late on Sunday afternoon through Monday morning.

Critical thickness values will be south of the area on Sunday, which
indicates precip will mainly consist of snow. They gradually lift
north into central WI by early Monday morning before surging north
by midday Monday.  This indicates precip type will transition to a
wintry mix or all rain during the day on Monday.  Interestingly,
probabilities for sleet or freezing rain are quite low during this
ptype transition phase, most likely due to the southeast low level
flow rather than flow out of the northeast.

Before the precip transition phase occurs, forecast QPF is rather
robust, with a greater than 50% chance of greater than 0.60 inches
of liquid equivalent over north-central WI.  This would indicate
significant snow accumulations are possible, if not likely,
northwest of the Fox Valley where boundary layer temps will be
relatively colder.  NBM and WPC both indicate relatively high
probabilities (60-80%) of greater than 6 inches of snow by 7 am
Monday and that seems plausible given the forcing and above normal
PWATS. Therefore, confidence is growing that winter headlines will
be needed for this time period.

Rest of the forecast...The cyclone will track northeast across
northwest Wisconsin on Monday night placing most if not all of the
area in the warm sector of the cyclone.  Ptypes therefore look to be
rain before colder air returns on the southern flank of they system
for Tuesday.  Light snow accumulations will be possible as this
colder air returns, mostly over north-central WI.

Quieter weather returns for Wednesday and Thursday with temps near
to slightly above normal.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1004 PM CDT Thu Mar 21 2024

Light snow will be ongoing in central WI at the beginning of the
TAF period, and will continue to spread north and east during the
first few hours. Conditions will deteriorate rapidly as the
steadier snow arrives, with flight conditions dropping to IFR/LIFR
during the peak period, which should occur late tonight through
mid-morning Friday. The heaviest snow, with accumulations of 3 to
5 inches, should occur south of Hwy 29. The snow will gradually
decrease in intensity on Friday, but is not expected to end until
mid to late afternoon west, and Friday evening in eastern WI.
Flight conditions are expected to improve to VFR from NW to SE
during the late afternoon and evening, though MVFR conditions may
persist in EC WI through the end of the TAF period.

East to southeast winds should remain below 10 knots through the
event, so potential for blowing/drifting snow will be low.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 1 PM CDT this afternoon for WIZ010-
011-013-018>022-030-031-035>040-045-048>050-073-074.
&&

$$

DISCUSSION.....JLA/MPC
AVIATION.......Kieckbusch


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.