799
FXUS63 KGRB 161712
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1212 PM CDT Thu May 16 2024

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Thunderstorms are possible across the forecast area today. A few
  storms may become strong or severe in central and east central
  Wisconsin in the late afternoon. Hail and strong winds are the
  main hazards.

- On and off rain/storm chances will continue through the middle
  of next week. It is too early to determine if any of these
  storms may become severe.

&&

.DISCUSSION...
Issued at 357 AM CDT Thu May 16 2024

Short Term...Today...Tonight...and Friday

Showers and elevated thunderstorms are expected in central and
northcentral Wisconsin this morning, and in east central and
northeast Wisconsin during the early to mid afternoon hours ahead
of a northeastward moving warm front. These storms could have
brief heavy rain and small hail.

A surface trough (not really a cold front, as the air behind it
is not any cooler) will approach the area in the late afternoon
and could produce a scattered to broken line of thunderstorms in
central Wisconsin in the late afternoon and in east central
Wisconsin in the early evening hours. The storms along this front
could be strong or severe depending on how much instability there
is. Models do show dewpoints increasing to the low 50s, and CAPE
of 400 to 700 J/kg with 30 to 40 knots of shear. Large hail and
strong winds are the main threat if these storms materialize.

Temperatures today will probably rise and fall one or more times
as areas of showers move by. Highs will be mostly in the 60s,
except in the 50s near Lake Michigan. CLearing skies are expected
tonight as the front goes by. Lows will be in the 40s. Friday
should be sunny and warm as winds become southwest and 850mb
temperatures climb into the low teens. High temperatures should
reach the 70s, except cooler near the Lake Michigan shore.

Long Term...Friday Night Through Wednesday

An active spring pattern with multiple rounds of rain and storms
to remain in place through the extended. Main change from
previous forecasts revolves around models trending drier for this
weekend`s system. Focus then turns to more robust precip chances
mid-week, although there is still significant model spread with
precip timing and amounts.

Weekend precip chances... Weekend rain/storm chances associated
with a surface low passing to our north are looking considerably
less impressive than in previous forecasts. Ultimately, it looks
like weak high pressure and dry air building in behind the
departing system are winning the battle with any moisture located
along the leading edge of the cold front. This being said, windows
for clearing during the day paired with a surge of warm temperatures
in the upper 70s to low 80s will result in some surface-based
instability (~600 to 1000 J/kg CAPE). While organized severe
weather is not currently expected, favorable surface instability
paired with weak elevated cold air advection may be enough to
generate some pulse thunderstorms across portions of central and
north-central Wisconsin. Any thunderstorm activity is expected to
be short-lived, especially as instability diminishes with the loss
of daytime heating.

Next week... On and off rain/storm chances will continue through
mid- week, although forecast confidence significantly drops off
past the weekend. A weak shortwave is expected to bring a round of
light rain to much of the forecast area on Monday before
attention then turns to a more dynamic system that will eject up
from the central Plains to the Great Lakes by Wednesday morning.
The track and strength of this system are extremely variable this
far out in the forecast period, and will largely depend on how
quickly weak high pressure ahead of the system erodes earlier in
the week. Will continue to monitor for storm potential as we get
closer to the event.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1212 PM CDT Thu May 16 2024

Showers and thunderstorms will track through the east-central
Wisconsin TAF sites early this afternoon, with additional showers
and thunderstorms possible later this afternoon into early this
evening as an occluded front tracks through the region. Any
remaining showers and thunderstorms will end from west to east
during the afternoon and early evening as the occluded front moves
to the east and high pressure builds in from the west. Flight
conditions will likely vary from VFR where there isn`t much shower
or thunderstorm activity, to MVFR/IFR in shower and thunderstorm
activity.

Clearing skies are expected overnight along with light winds. This
will provide ideal conditions for fog development given the recent
rainfall. Therefore will put in low clouds and fog across the TAF
sites overnight with IFR/LIFR conditions, with the fog expected
to dissipate by 15Z Friday. VFR conditions are then expected after
the fog lifts on Friday.

&&

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

&&

$$

DISCUSSION.....RDM/Goodin
AVIATION.......Kurimski