421
FXUS63 KGRB 081141
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
641 AM CDT Wed May 8 2024

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- An unsettled weather pattern will bring intermittent chances of
  light rain from today through the weekend. There is a slight
  chance of thunderstorms over central and north-central Wisconsin
  this afternoon, but severe weather is not expected.

- Low temperatures in the lower to middle 30s will be conducive
  for a frost and freeze over north-central and far northeast
  Wisconsin on Thursday night.

&&

.DISCUSSION...
Issued at 338 AM CDT Wed May 8 2024

Short Term...Today...Tonight...and Thursday

Precipitation trends and temperatures will be the main forecast
concerns during the short-term period.

An upper level low pressure system and mid-level frontogenetic
forcing will gradually shift out of far N/NE WI early this
morning, resulting in a gradual decrease in the rain band that
lingers there. Patchy dense fog in north central WI should mix
out by mid-morning, and a Special Weather Statement has been
issued through the commute period. After a short dry period
through midday, a few showers and isolated thunderstorms may
redevelop over the southwest half of the forecast area, where an
inverted surface trough and weak instability (SBCAPE 100-400 j/kg)
will reside in the afternoon and early evening. Most of the
shower activity should wane after sunset, though isolated showers
may linger over the far southern part of the forecast area
overnight. Models have trended farther south with the next round
of precipitation on Thursday, so have lowered pops to slight
chance/chance and shifted precipitation chances a bit farther
south. It`s possible that further southward adjustments may be
needed, due to dry NE winds.

Persistent clouds over northern WI should hold temperatures in
the lower to middle 60s over northern WI today, while partly
cloudy skies and sunshine boosts highs into the lower to middle
70s farther south. Lows tonight should be in the upper 30s far
north to the 40s elsewhere. Mostly cloudy skies and brisk NE winds
(especially in the Fox Valley and lakeshore areas) will bring
cooler highs in the 50s to around 60 range on Thursday.

Long Term...Thursday Night Through Tuesday

Weather impacts in this part of the forecast mainly revolve around
frost potential and light precip chances.

Frost Potential:  Clouds will be departing Thursday evening from
north to south.  As the surface ridge axis arrives overnight, nearly
ideal radiational cooling conditions will be in place over central
to north-central Wisconsin.  Forecast low temperatures remain in the
lower to middle 30s over the sandy soil areas of north-central to
far northeast WI.  These temps will be favorable for frost
development.  Anyone with cold sensitive plants are advised to take
proper precautions.

A similar setup could be in store on Saturday night as well, as a
weak surface ridge axis is forecast to move into the region late.
Forecast temps are few degrees warmer than on Thursday night, but
MOS guidance indicates temps in the middle 30s are possible.

Light precip chances: A quick hitting clipper system remains on
track to bring rainfall to the region on Friday afternoon into
Saturday morning.  Decent dynamics combined with weak instability up
to 100 j/kg could lead to isolated storms and will leave a slight
chance of thunder in the forecast.  A tenth to a quarter inch of
precip appears possible for most locations.

Another quick hitting system could generate light rain on Sunday
afternoon and evening, but dynamics are not nearly as robust as on
Friday night.  Precip chances will therefore be lower.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 632 AM CDT Wed May 8 2024

Rain was finally coming to an end across far NE WI early this
morning, but low clouds remained over parts of northern WI, and
patchy dense fog was ongoing over the western part of the forecast
area. The fog should mix out by 14z, and low clouds in northern
WI should gradually rise to VFR by midday. There is a small chance
of showers or a stray thunderstorm this afternoon and early
evening, mainly over central WI. A few showers could redevelop
across central and east central WI overnight.

Winds will become E-NE this afternoon and tonight, and may become
gusty in the Fox Valley tonight.

&&

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

&&

$$

DISCUSSION.....Kieckbusch/MPC
AVIATION.......Kieckbusch