555
FXUS63 KGRB 091959
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
259 PM CDT Thu May 9 2024

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- A frost or freeze is likely across far northern Wisconsin late
  tonight.

- An unsettled weather pattern will bring intermittent chances of
 showers and a few thunderstorms through the weekend. Severe
weather is not expected with any of these thunderstorms, but we
will be watching for the potential for strong storms on Sunday.

- Due to the recent rainfall, river levels remain elevated. Some
  rivers may reach or surpass bankfull.

&&

.DISCUSSION...
Issued at 259 PM CDT Thu May 9 2024

Short Term...Tonight and Friday

Sprinkles will end and skies will clear as an upper trough exits
the region this evening. Low level convergence across central
Wisconsin may keep skies from clearing until 09z, which may
diminish their frost potential. Decided to issue a freeze warning
for Vilas, Oneida, Forest and Florence counties, and a frost
advisory for one row of counties to the south.

Sunny skies are expected Friday morning, but clouds will increase
in the afternoon as an upper trough and surface front approach
from the northwest. Showers should arrive in central and north
central Wisconsin by late afternoon, and in the evening further
east. The upper trough looks quite dynamic, but there is little
warm advection or moisture advection ahead of it. Instability
should be sufficient for scattered thunderstorms but the severe
threat looks low.

Highs temperatures will be in the early afternoon near Lake
Michigan where a lake breeze will move inland, and across far
northcentral WIsconsin where clouds and rain are expected.

Long Term...Friday Night Through Thursday

Intermittent active weather continues in the extended period. A
surge of warmer air will bring the first chance to see the 80s
this year.

Active weather...

Rain will likely be ongoing Friday night as a shortwave works its
way across the region. Minor instability, around 100 to 350 J/kg
of CAPE, could allow for a few rumbles of thunder early on, but
any remaining thunder chances will end fairly quickly overnight.
Rain amounts around a tenth to a quarter of precip remain
reasonable for this system. Quiet conditions then return by the
late overnight hours through Saturday afternoon.

Diurnal heating and a passing secondary shortwave will bring the
next chance for some rain Saturday afternoon. Instability will be
mainly surface based as temperatures get into the middle to upper
60s and low level lapse rates increase, but with little to no
instability aloft to work with thunder seems unlikely. In the end,
expect an increase in cloud cover with a few isolated to scattered
light showers that dissipate as we get past sunset.

Sunday will also see a chance for active weather in the
afternoon. Southwesterly accompanying a warm front early in the
day will bring a surge of warmth and moisture to the region, in
particular to the lower levels. That said, mixed layer instability
will remain more modest, which will help limit storm strength and
shear values will be relatively low, so organized storms seem
unlikely. In short, severe weather threat still appears relatively
low. However, this environment could produce a few pulse like
storms, which would carry the potential for some stronger wind
gusts when a storm rains itself out. Scattered rain and storm
activity then continues into the evening to early overnight hours.

Finally, the next more widespread system will cross into the
region sometime in the middle of next week.

Temperatures...
Temperatures will be warmest on Sunday, thanks to some potentially
strong southwesterly flow. This will bring highs in the 70s and
could also bring a few to around 80, which would be the first time
seeing 80 degrees in northeast Wisconsin so far this spring.
Somewhat cooler conditions then follow for the rest of the week,
with highs in the upper 60s to lower 70s for the rest of the
period.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1244 PM CDT Thu May 9 2024

VFR conditions are expected through at least midday Friday.
Clouds will clear from north to south tonight, with clouds
remaining longest over central Wisconsin.

An approaching cold front will bring MVFR conditions, showers and
scattered thunderstorms west of an Iron Mountain to Wisconsin
Dells line Friday afternoon, and further east Friday evening.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Freeze Warning from midnight tonight to 7 AM CDT Friday for
WIZ005-010>012.

Frost Advisory from midnight tonight to 7 AM CDT Friday for
WIZ013-018-019-021.
&&

$$

DISCUSSION.....RDM/Uhlmann
AVIATION.......RDM