000
FXUS63 KGRB 151126
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
626 AM CDT Mon Apr 15 2024

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Elevated fire weather conditions continue today. Mild
  temperatures, along with relative humidity values of 18 to
  30 percent away from Lake Michigan are expected during the
  afternoon and early evening hours. Winds will be lighter with
  gusts only around 15 mph.

- Elevated fire weather conditions will persist into Tuesday
  across northern Wisconsin due to low relative humidity and
  increasing easterly winds.

- Showers and a few embedded thunderstorms are expected from
  Tuesday afternoon into Wednesday. Widespread severe weather is
  not expected, but strong winds aloft could mix to the surface
  with any storms or heavier showers. Heavy rainfall will be
  likely regionwide.

- Strong east to southeast winds are expected Tuesday into
  Tuesday  night, with gusts of 30 to 45 mph. The strongest gusts
  are  anticipated across central Wisconsin.

&&

.DISCUSSION...
Issued at 412 AM CDT Mon Apr 15 2024

Short Term...Today...Tonight...and Tuesday

Except for some clouds across far northeast Wisconsin, skies were
clear early this morning. Temperatures at 3 am ranged from the
upper 20s across Vilas County to the lower 40s across the Fox
Valley.

For today, another day of elevated fire weather conditions with
high temperatures in the 60s to lower 70s. The afternoon relative
humidity values will drop into the 18 to 30 percent range away
from Lake Michigan and the bay of Green Bay. The big difference
from yesterday is that winds will be lighter with gusts around
15 mph. Across northeast Wisconsin, will need to watch for a wind
shift to the east or northeast as bay/lake breeze is expected to
push inland during the afternoon and early evening.

For tonight, skies will vary from partly to mostly cloudy at times.
Lows tonight should drop into the 30s to lower 40s, although
temperatures will probably rise a few degrees overnight as east
winds will be on the increase. On Tuesday, a strong low pressure
system across the central plains will move slow east into Iowa.
The pressure gradient between a 1029 mb high across eastern Canada
and the 992mb low across Iowa will lead to increasing easterly
winds on Tuesday. Winds should be in the 15 to 25 mph range with
gusts of 25 to 35 mph with locally higher gusts during the
afternoon. The chances of rain will be on the increase in the late
morning across central Wisconsin and then across much of the area
Tuesday afternoon. The rain is not expected to reach far
northeast Wisconsin until early evening. There is also a small
chance of thunderstorms during the afternoon across central
Wisconsin. Severe storms are not expected.

Long Term...Tuesday Night Through Sunday

The main forecast concern for the extended will be dealing with
the incoming low pressure system Tuesday evening through
Wednesday that will bring widespread heavy rainfall, scattered
thunderstorms, and strong east to southeast winds.

Although some rain may already be on its way across central WI in
the afternoon, the bulk of the rainfall will arrive Tuesday
evening and continue overnight. A strengthening low level jet
ahead of the low will bring a surge of moisture into the region
and generate fairly strong isentropic ascent over the region. Instability
will be limited, with only the NAM suggesting some MUCAPE at 500
j/kg or less across portions of central to east- central WI, so
suspect any thunder will be limited to embedded storms in the
widespread rainfall. Although severe storms are not expected,
with winds at 925mb and 850mb around 40 to 50 knots, it will still
be possible to see isolated strong wind gusts reach the surface.
The wind will likely also result in at least a high end small
craft advisory. With PWATs to around 1 to 1.3 inches, heavy rain
does seem likely in the region as well, especially with any
embedded thunderstorms. A widespread 1 to 2 inches of rainfall is
in the forecast from late Tuesday night through Wednesday. The low
will progress across Wisconsin Wednesday. As the low occludes,
some lingering precipitation will remain in the region through
Wednesday, along with a rumble of thunder or two in the afternoon.
That said, winds and rain rates will be considerably less
Wednesday than they were Tuesday evening and overnight.

As the remnants of this system head north into Canada it will
ultimately phase with another slow moving system, resulting in a
broad slow moving low pressure system to our north. This will
shift the general flow to the west and northwest, bringing us some
cooler air and a lingering chance for precipitation near the Upper
Peninsula border, although this may yet stay to far north. If we
do see some light precipitation late Thursday night and Friday, it
may include some brief light snow. Dry conditions then finally
return to the region for next weekend.

Temperatures in the extended will start off above normal Wednesday
and cool to near normal by the end of the week.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 622 AM CDT Mon Apr 15 2024

VFR conditions will continue through Tuesday morning. Rain
is expected to move northeast into the area, mainly Tuesday
afternoon with rain and a few thunderstorms expected Tuesday
night and Wednesday. For today, winds will be from the north
or northwest, with a lake/bay breeze turnings winds to the
northeast or east this afternoon. Later tonight and Tuesday
easterly winds will be on the increase with gusts over 30
knots possible Tuesday afternoon and Tuesday night. CIGS
are expected to deteriorate into the MVFR category or lower
later Tuesday night into Wednesday.

&&

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

&&

$$

DISCUSSION.....Eckberg/Uhlmann
AVIATION.......Eckberg