154
FXUS63 KGRB 110350
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1050 PM CDT Fri May 10 2024

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

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

&&

.DISCUSSION...
Issued at 259 PM CDT Fri May 10 2024

Short Term...Tonight and Saturday

A strong upper trough but weak surface trough will
move across the region during the late afternoon and early evening
hours and bring a short period of showers and thunderstorms. While
upper system is somewhat impressive, moisture is limited and low
level forcing is weak. So we expect a few storms with small hail
and wind gusts to 40 mph but severe storms look unlikely.

Those wishing to look for the Northern Lights will probably find
less clouds across the southern half of the forecast area
tonight. Lows will be in the 40s.

Saturday will be sunny and mild, with a small chance of an afternoon
shower near the lake breezes in east central Wisconsin. Highs will
be a few degrees above normal for this time of the year.

Long Term...Saturday Night Through Friday

Precipitation trends remain the focus of the extended forecast, in
particular for Sunday where a cold front will be passing through
during peak heating.

Precipitation Trends...

A warm front will bring a surge of warmer air into the region
Saturday night into Sunday morning. This could bring a few
scattered showers to the region by the warming but remain devoid
of thunder. Attention then turns to the development of
thunderstorms in the afternoon. Surface based instability
parameters will be the main thing to watch for Sunday, as these
will largely dictate the strength and impacts of any storms in the
afternoon and evening. The GFS and NAM both bring around 1500-2000
J/kg of SBCAPE into the region during the afternoon, but this is
heavily reliant on dewpoints surging from the middle 40s in the
morning to the upper 50s to lower 60s by the early to mid
afternoon. While this continues to seem overzealous, especially as
the ECMWF also keeps dewpoints in the middle 50s, this will bear
watching, especially as two of the major models now feature this
surge of higher moisture values. Deep shear values will remain
relatively low on the other hand, around 20 to 25 knots so
widespread severe weather seems unlikely. All together, Sunday
will have the potential for pulse thunderstorms, which could
produce some small hail and strong wind gusts. The ultimate
strength of the wind gusts and whether severe weather wording gets
added to the forecast will largely depend on the surface
parameters over the next couple forecast cycles.

Quieter conditions will follow this Sunday system. The next chance
for widespread rainfall will be late Wednesday into Thursday.

Temperatures...
Sunday continues to be the warmest day in the forecast, with highs
in at least the 70s everywhere and a few warm spots getting into
the lower 80s. Behind this, the rest of the forecast is mainly in
the upper 60s to lower 70s.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1049 PM CDT Fri May 10 2024

Showers with gusty winds have cleared the lakeshore. A few showers
may clip RHI, AUW and CWA as more showers drop in from northwest
WI while fading away. MVFR ceilings may impact areas north of a
Ironwood to Antigo to Green Bay line late tonight and early
Saturday morning, but VFR flight conditions are likely elsewhere.
Good flying weather is expected Saturday afternoon through Sunday
morning.

&&

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

&&

$$

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