024
FXUS63 KGRB 010135
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
835 PM CDT Tue Mar 31 2026

New Information added to update section

.UPDATE...
Issued at 828 PM CDT Tue Mar 31 2026

No changes to the Winter Storm Watch this evening. Precipitation
looks to arrive a little slower than the current forecast
indicates on Wednesday evening, but not sufficiently enough to
change headlines at this time. It will be interesting to see how
quickly temperatures warm on Thursday morning when strong lift,
and heavy precipitation will be occurring into easterly low level
flow. Wouldn`t be surprised if the warmer air surging from the
south is a little slower to arrive than advertised. Will pass
along thoughts to the mid-shift before making large-scale
changes.


&&

.KEY MESSAGES...

- A Winter Storm Watch has been issued for Wednesday night into
  Thursday for much of central, northeast and north central WI.
  Significant freezing rain and sleet accumulations are possible
  with this system. There will be potential for tree damage and
  power outages, and travel may become extremely hazardous.

- Thunderstorms will also be possible Thursday into Thursday
  evening, and may become strong in the Fox Valley and lakeshore
  areas.

- Another significant storm will bring potential for heavy
  rainfall, mixed precipitation and possible thunderstorms. Wintry
  impacts appear to be more focused over northern WI.

- Flooding concerns arise this weekend into early next week
  following the passage of the two moisture rich systems.

&&

.DISCUSSION...
Issued at 315 PM CDT Tue Mar 31 2026

The threat of thunderstorms has shifted southeast of the forecast
area and clouds were clearing from west to east. Temperatures were
40s and lower 50s, except upper 30s where low clouds persisted in
the far north and east.

Expect a break in the active weather tonight into Wednesday, with
below normal temperatures expected in the wake of today`s cold
frontal passage. There could be some pockets of low clouds later
tonight into Wednesday morning.

Winter Storm Potential Wednesday night into Thursday...A
Colorado Low brings the next chance for precipitation Wednesday
night through Thursday evening. Models have trended farther
northwest with the surface low, and track it through NE WI
Thursday evening. As the low approaches Wednesday night, strong
WAA/isentropic lift and FGEN will generate widespread heavy
precipitation, given unseasonably high PWATs of 0.9-1.3 inches.
Current temperature forecasts at the surface and aloft support
sleet and freezing rain over most of the forecast area, with the
most significant amounts occurring across central, north central
and far northeast WI, where probabilities of 0.25 inch of ice
have risen to 40-70 percent, and a half inch of ice to 20-40
percent. There could also be copious amounts of sleet with this
system, with accumulations of a 1/2 inch to an inch. Though it`s
not expected to be a huge factor in this storm, snow (combined
with sleet) accumulations could reach 2-4 inches in the far
north. Have issued a Winter Storm Watch for most of central, north
central and far northeast WI, with start/end times staggered from
earlier south to later north. The end times correspond with
surface temperatures rising above freezing, leading to a
changeover to all rain. Suspect that a Winter Weather Advisory
will be needed from Waushara County eastward through the Fox
Valley and lakeshore areas, where sub-warning accumulations of
sleet and freezing rain are expected. Will hold off on issuing
that at this time, as slightly cooler or warmer temperatures could
greatly alter the forecast. Given the farther northwest track of
the system, at least the southeast portion of the forecast area
appears likely to get into the warm sector Thursday afternoon and
early evening, leading to the potential for surface-based
thunderstorms, some possibly strong to severe.

Another Significant Storm Expected Late in the Week...In case you
haven`t had enough by this time, another Colorado Low is expected
to impact the region late Friday into Saturday. This system will
also bring warmer and very moist air to the region, as the Gulf
will still be open. Similar to the midweek system, there are
uncertainties in low track and thermal profiles, but northern WI
appears to have the greatest chance of having significant wintry
impacts with this system.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 600 PM CDT Tue Mar 31 2026

Primary forecast challenge revolves around the southern extent of
MVFR stratus overnight into Wednesday morning. Currently, a cold
front has pushed south of the region with high pressure building
in from northern Ontario. While clearing has occurred over central
and northeast Wisconsin, a deck of low clouds is surging south
across the far north. Guidance remains mixed on how far south this
stratus penetrates, but maintained a period of MVFR conditions
for the Fox Valley and central Wisconsin terminals roughly between
08Z and 16Z. Any lingering low ceilings should erode by late
Wednesday morning as mixing occurs into a drier airmass aloft.

Otherwise, VFR conditions will prevail through much of Wednesday
with an increase in mid and high clouds during the afternoon.
Ceilings will gradually thicken and lower toward the end of the
period as a potent storm system approaches from the southwest.
Precipitation is expected to develop across the terminals by mid
to late evening as the low level airmass saturates. Surface winds
will remain northerly tonight before veering easterly on
Wednesday, with some gusts to 15-20 kts possible at times.

Confidence is medium regarding the duration and southward
progress of the morning stratus.

Outlook...Widespread IFR/LIFR conditions are expected Wednesday
night through Thursday as a major winter storm brings a heavy
wintry mix to the region.

&&

.HYDROLOGY...
Issued at 315 PM CDT Tue Mar 31 2026

Despite the uncertainty in p-types, the two well-saturated
systems this week will lead to flooding concerns, with a signal
for river and stream rises this weekend into early next week
across the forecast area. Minor flooding would likewise be
possible in low-lying and poor drainage areas.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from late Wednesday night through Thursday
afternoon for WIZ005-010>013.

Winter Storm Watch from late Wednesday night through Thursday
afternoon for WIZ018>021-030-031-073-074.

Winter Storm Watch from Wednesday evening through Thursday
morning for WIZ035>037.
&&

$$

UPDATE.........MPC
DISCUSSION.....Kieckbusch
AVIATION.......MPC
HYDROLOGY......Kieckbusch

NWS GRB Office Area Forecast Discussion