268
FXUS63 KGRB 242352
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
652 PM CDT Fri May 24 2024

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Occasional showers and thunderstorms are expected into the
  evening hours. Brief gusty winds and heavy downpours are
  expected.

- Memorial Day weekend starts off dry for Saturday, but rain
  chances increase by Sunday afternoon and continue into Memorial
  Day. A soaking rain could occur during this time.

- A few rivers over central and eastern Wisconsin could surpass
  minor flood stage early next week.

&&

.DISCUSSION...
Issued at 319 PM CDT Fri May 24 2024

Short Term...Tonight and Saturday

A negatively tilted upper trough and attendant surface front will
produce a broken line of thunderstorms as it moves across the
area into the evening hours. Showers and thunderstorms that moved
across the region earlier today and cloud cover have kept the
lower atmosphere stable through mid afternoon, but increasing
moisture convergence and and warm advection ahead of the front
should create enough instability to get things going by 22z or
23z. Strong winds and hail are the main threats from this system.

The activity will end by late evening, and cLearing skies and
drier air will arrive overnight. Low temperatures should be a few
degrees below normal. Saturday should be mostly sunny and a bit
breezy with seasonable temperatures. There could be a stray shower
in far northcentral Wisconsin.

Long Term...Saturday Night Through Friday

A 500mb trough will swing into the area late Saturday night into
Sunday morning, then move across the western Great Lakes Sunday
into Memorial Day. Beyond Memorial Day, ridging is expected across
the plains which will result in the western Great Lakes being in
a north/northwest flow pattern. The ridge should then shift east
into the western Great Lakes by Friday of next week. Temperatures
through the middle of next week will run at or slightly below
normal, then would likely trend warmer than normal late next week.

For Saturday night, a weak surface boundary will be lurking across
the far north. Per coordination with Marquette and Duluth, will
have a small chance of showers and thunderstorms across the far
north for a few hours into the evening. Dry conditions will
prevail overnight. The next system approaches from the south
Sunday morning. By noon, there will be chances of rain across
much of the area west of an Eagle River to Algoma line, with a
widespread rain event expected Sunday afternoon and evening.
There are some difference in the track of the low that could
impact rainfall amounts and also the possibility of some stronger
storms across eastern Wisconsin. Rainfall totals over an inch are
possible across much of the area Sunday afternoon and Sunday
night. This will cause rivers to rise again with several reaching
bankfull stage and at least a few rivers could reach flood stage
early next week.

On Memorial Day, the northwest flow pattern will result in more
convection developing during the day with a cool air aloft. Some
of these storms could produce gusty winds and possibly some small
hail. Confidence is not high enough to add to the Hazardous Weather
Outlook. The cool cyclonic flow combined with daytime heating may
trigger some more showers and perhaps a few storms on Tuesday.
Dry conditions are expected Wednesday and Thursday with the next
chance of rain on Friday. Frost may be possible across the north
Thursday morning as the latest guidance would suggest lows in the
middle to upper 30s.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 642 PM CDT Fri May 24 2024

Showers and embedded thunderstorms were occurring over the eastern
two-thirds of the forecast area early this evening, and a
scattered line of showers was noted along a cold front in western
WI. The threat of severe storms has diminished, but brief gusty
winds, heavy downpours and MVFR flight conditions may accompany
any storms as they impact the GRB/ATW/MTW TAF sites this evening.
The precipitation will end from west to east later this evening
and into the early overnight as the cold front moves through.
There could be a brief period of post-frontal MVFR ceilings in NC
WI, but a general clearing trend is anticipated overnight.

Southeast winds will become gusty from the west after the frontal
passage, then turn S-SW in the mid to late afternoon on Saturday.
A brief period of LLWS is expected in far eastern WI this evening,
then over the northwest half of the forecast area overnight into
Saturday morning.

&&

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

&&

$$

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