417
FXUS63 KGRB 081949
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
249 PM CDT Mon Jul 8 2024

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Thunderstorms are possible through early this evening. Heavy
  rainfall, gusts to 40 mph and small hail are possible.

- On and off chances for showers and thunderstorms will continue
  Tuesday through Thursday. Although the severe weather threat
  remains low, locally heavy rainfall will be possible.

- Some rivers, creeks, and streams across east-central Wisconsin
  will continue to run above bankfull due to recent rainfall.

- A warmer/drier period may be in store toward the end of the week
  and into the weekend.

&&

.DISCUSSION...
Issued at 248 PM CDT Mon Jul 8 2024

Short Term...Tonight and Tuesday

Precipitation/thunderstorm trends are the main forecast concern,
along with the potential for fog later tonight.

The MCV that brought heavy rain to parts of northeast WI has
shifted out of the region, but additional thunderstorm development
was occurring. A small cluster of storms was moving into the Fox
Valley, and more numerous showers and storms were forming in NC
WI, in association with a short-wave trough and weak surface
boundary. The stronger storms were producing torrential downpours,
brief gusty winds and small hail, in an environment characterized
by SBCAPE of 1200-1800 j/kg and modest deep layer shear around
25-30 kts. Kept the highest pops in NC WI through the afternoon,
with lower chance pops farther southeast. The overall activity
should wane as the short-wave shifts east and daytime instability
decreases this evening.

Partial clearing, lingering low-level moisture from recent heavy
rain and light winds should lead to patchy/areas of fog later this
evening and into the overnight. The fog should be most extensive
in the climatologically-favored Wisconsin River Valley (NC/C WI),
but will mention at least patchy fog over the entire CWA. Lows
tonioght should range from the lower to middle 50 northwest to
the lower 60s southeast.

After a dry period late tonight into Tuesday morning, increasing
afternoon instability should lead to isolated/scattered
thunderstorms. The best chance of storms should occur in the
favored convergence area over far NE WI, where a weak short-wave
and the RRQ of an upper jet will also reside. Not expecting any
severe weather, as SBCAPE of 500-1000 j/kg and deep-layer shear
of 15 to 20 kts is not too impressive. High temperatures should
reach the upper 70s to middle 80s.

Long Term...Tuesday Night Through Monday

Although the remnants of Beryl are forecast to miss us well to the
southeast, a mid level PV anomaly combined with SBCAPEs around
1000 J/kg could generate scattered showers and thunderstorms
across the area on Wednesday. Bulk shear values on Wednesday will
be fairly weak, only 20 knots, so severe thunderstorms are not
expected.

Another round of isolated showers and thunderstorms is possible
Thursday afternoon with SBCAPEs of 1000 to 1500 J/kg and only 15
knots of bulk shear. However, forcing will be weaker than
Wednesday so coverage is not expected to be as high. Dry weather
is then expected to close out the week as high pressure builds in
across the Great Lakes.

As the high drifts east, it will allow warm temperatures to surge
into the region from the south as dew points also increase. This
will allow temperatures to soar well into the 80s this weekend
into early next week, with a few 90s possible on Sunday and Monday.
Dew points will surge into the 60s on Saturday and into the lower
70s on Sunday and Monday across portions of central and east-
central Wisconsin. The combination of heat and humidity will cause
heat index values to rise well into the 90s across central and
east- central Wisconsin Sunday and Monday afternoon.

In addition to the heat and humidity, shortwaves tracking along
the periphery of the ridge will bring the chance for showers and
thunderstorms back to the region from Saturday through next
Monday. The best chances will be during the afternoon and evening
hours when instability is maximized.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1228 PM CDT Mon Jul 8 2024

A line of strong thunderstorms associated with an MCV was pulling
out of far NE WI at issuance time. Additional scattered showers
and isolated storms were ongoing across the forecast area. Showers
and storms should be most numerous in north central WI this
afternoon, as a weak boundary and upper trough impact the region
during peak heating. Expect convection to weaken after sunset,
with the loss of daytime heating/instability.

Light winds, low-level moisture, recent rain and partly cloudy
skies should set the stage for fog development overnight,
especially in the Wisconsin River valley of NC/C WI. The fog
should mix out rapidly by around 13z/Tuesday. Scattered cumulus
development is expected to occur later in the morning, but any
daytime convection should hold off until afternoon.

&&

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

&&

$$

DISCUSSION.....Kieckbusch/Kurimski
AVIATION.......Kieckbusch