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000
FXUS63 KGRB 090921
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
421 AM CDT Tue Apr 9 2024

Forecast discussion for routine morning forecast issuance

.KEY MESSAGES...

- Confidence is increasing in a strong low pressure system lifting
  into the Great Lakes region Thursday into Friday. If the
  westerly track holds, widespread rainfall and strong wind gusts
  can be expected. A rumble of thunder is not out of the question.

- Above normal temperatures will continue into next weekend. Highs
  could reach 70 in spots Wednesday and Sunday inland from Lake
  Michigan.

&&

.DISCUSSION...
Issued at 420 AM CDT Tue Apr 9 2024

Short Term...Today...Tonight...and Wednesday

An upper trough rotating around an upper low north of the Minnesota
Arrowhead was producing scattered showers over northern Wisconsin
at 0900z. There were even a few elevated thunderstorms over northern
Lower Michigan. This activity should diminish this morning as the
trough moves off to the east. There are quite a bit of clouds upstream,
so it will likely be a mostly cloudy day. High temperatures will be
3 to 5 degrees above normal.

A jet streak moving across southern Wisconsin could produce isolated
showers in central Wisconsin this evening, but otherwise dry conditions
are expected tonight, with clearing after midnight. Low level warm
advection and evening clouds will make for low temperatures 5 to 10
degrees higher than average.

Wednesday will be a mild day, with sunshine followed by increasing
clouds. 925mb temperatures suggest that temperatures cloud get
close to 70F in the Fox Valley.

Long Term...Wednesday Night Through Monday

The main focus of the extended period will be the passage of a
strong low pressure system in the Thursday to Friday time period.

A strong low pressure system will lift out of the Central Plains
Wednesday night into Thursday, arriving in the Great Lakes region
by late Thursday morning. The track of the low continues to show
signs of shifting westwards, as a trailing shortwave phases with
the system during the day Thursday. The main impacts of this
westward shift will be more widespread precipitation for the
period and an increase in wind gusts, especially for eastern
Wisconsin. There is potential for a period of wind gusts near 40
mph in the overnight period as the center of the low passes the
region. The good news here is that unlike the similar system from
last week, we will be much warmer this time around so no snow is
expected. Thunder on the other hand remains in question as
instability will be fairly limited but the dynamics may yet be
enough to produce a rumble or two.

Behind the passage of the low, quieter conditions are expected by
around midday Friday through Saturday. There may be another quick
hitting shortwave over the weekend, which will be helped by some
additional moisture and well above normal temperatures. Highs by
Sunday could touch into the low 70s for portions of the region!
Finally, return flow arrives again for early next week, which will
setup the next chance for a larger system to arrive in the area.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1032 PM CDT Mon Apr 8 2024

Weakening low pressure lifting north over Minnesota will support a
few showers over central and north-central WI into far northeast
WI through daybreak. Conditions which are mainly VFR late this
evening, will trend MVFR or even IFR later tonight at CWA, AUW
and RHI while staying VFR elsewhere. A brief few hour window of
MVFR even at GRB and ATW on Tuesday morning, but otherwise, all
TAF sites will trend VFR during Tuesday afternoon.

In terms of winds, prevailing southerly winds will veer to
westerly following the passage of a cold front Tuesday morning.
Some breezy conditions may be possible in wake of the frontal
passage, with potential for 20 knot gusts at most of the TAF
sites.

&&

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

&&

$$

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