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000
FXUS63 KGRB 232337
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
637 PM CDT Tue Apr 23 2024

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- The chance of showers and storms will continue through early
   this evening before exiting east-central Wisconsin by 9-10 pm.
   The atmosphere will be favorable for gusty winds out of any showers
   and storms to around 45 mph. Small hail is also possible out
   of the strongest storms.

 - Elevated fire weather conditions are likely Wednesday and
   Thursday due to relative humidities ranging from 15 to 25
   percent. However, relatively light winds and cool temperatures will
   keep conditions below critical levels.

 - Two systems will bring periods of showers and thunderstorms to
   the forecast area Friday through Monday. Watching the
   potential for severe weather on Saturday, although it is still
   too soon to tell.

&&

.DISCUSSION...
Issued at 224 PM CDT Tue Apr 23 2024

Short Term...Tonight and Wednesday

The latest RAP analysis and satellite/radar imagery show a dynamic
upper trough moving across the western Great Lakes early this
afternoon. The trailing cold front is entering far northern
Wisconsin. Showers and thunderstorms developed by late morning
across north-central and far northeast Wisconsin and continued to
expand in coverage into the early afternoon hours as temps reached
their convective temps. Due to deep mixing (estimated at up to
600mb!!), the showers were high based and produced gusty winds
upwards of 40 mph. Have not received any reports of hail, but
storms in the Upper Peninsula produced three quarters inch hail.

The showers and storms will continue to move southeast for the
rest of the afternoon. Even light showers will be capable of
producing gusty winds to 40 mph as the lower atmosphere will be
supportive of evaporative cooling. Small hail will also be
possible in the strongest storms, but this threat is will be more
confined to central and east-central WI where precip has been more
widely scattered.

Clouds and precipitation: Showers and a few storms will rapidly
exit east- central Wisconsin this evening. Gusty winds and small
hail will be possible but the threat should wane rapidly as
nocturnal cooling sets in. Most showers will exit by the 8-9 pm
hour.

Then a very dry airmass (pwats 20-30% of normal) will move into
the region from the north for the rest of the night. After a
period of mostly cloudy skies behind the front, skies should
rapidly clear late this evening into overnight. Clear skies are
then expected for Wednesday.

Temperatures: No significant changes to the previous forecast.
Don`t think winds will fully decouple tonight, so remained close
the NBM. On Wednesday, low level temps are colder over eastern WI
due to north winds and the previous forecast already showed this
well.

Long Term...Wednesday Night Through Tuesday

An active pattern is expected to set up toward the end of the
work week and persist through early next week. Multiple chances
for rain and thunderstorms will accompany several systems that are
progged to track from the central Plains into the upper Midwest
through Monday. Watching potential for severe weather on Saturday,
although currently too far out in the forecast period to discern
any details. Temperatures will begin a steady incline through the
end of the week before peaking in the mid 70s (~15 degrees above
average) on Saturday given favorable placement in the warm sector.

Friday/Saturday precip... Main focus for the extended is an end of
week system that will bring rain and storm chances to the forecast
area, including potential for some severe weather on Saturday. A
robust upper-level shortwave will spin up a surface low over the
central Plains before trekking into the upper Mississippi Valley
Saturday morning. Current model guidance seems to be targeting
portions of northeast Wisconsin to receive the bulk of the QPF
(~0.6 to 1") from this system, although there is still some
disagreement about when precip arrives on Friday. Suspect that QPF
may trend on the higher end of what ensembles are currently showing
given deep Gulf moisture placing around 1.3" PWATs across most of
eastern Wisconsin. Some elevated storms would be possible Friday
afternoon/evening out ahead of the warm front, although most
convective elements look to come together on Saturday. A trailing
cold front is progged to move east across the warm sector during
peak heating Saturday afternoon, providing a source of lift for
surface-based convection. Additional ingredients (CAPE, lapse
rates, shear) also look to be in relatively good shape for
Saturday, although it is still too soon to tell for certain.
Southeast winds will begin to ramp up Friday afternoon as the
pressure gradient tightens between the leading edge of the
approaching surface low and departing high pressure to the east.

Sunday/Monday precip... A brief lull in precip is expected to set
in Saturday night to Sunday morning before a second system trails
from the Four Corners region into the upper Midwest by Monday
morning. There are still timing issues this far out in the
forecast period, although there is a strong signal for periods of
moderate to heavy rainfall across northeast Wisconsin.
Thunderstorms look to be possible across eastern Wisconsin Monday
afternoon, although this could change as models hone in on timing.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 628 PM CDT Tue Apr 23 2024

Showers and isolated thunderstorms will continue to move through
the southeast part of the forecast area early this evening, and
should completely exit the area by 02z-03z. Brief gusty winds
will accompany some of the showers.

A strong cold front was dropping south through central and east
central WI, accompanied by wind gusts to 25 to 35 kts. The gusty
winds will persist through the evening, but should gradually
decrease in intensity.

MVFR ceilings covered much of north central and far northeast WI
at issuance time, and will likely make a push to the south this
evening. The low clouds should erode later this evening, except
along the lakeshore, where they may persist into the overnight
hours. By late tonight, the entire forecast area should be clear,
and winds should be light, except in the Fox Valley and lakeshore
areas.

&&

.FIRE WEATHER...
Issued at 224 PM CDT Tue Apr 23 2024

Another period of elevated fire weather conditions is likely on
Wednesday and Thursday due to a very dry airmass that will move
into the region. Afternoon RH values of 15 to 30 percent are
likely on Wednesday, but cooler temps are anticipated in the
lower 40s lakeside to the low 50s inland. On Thursday, RH values
will be slightly higher between 25 to 35 percent, but temps and
winds will both be slightly higher. While RH`s will be near to
below critical criteria, winds and temps should remain below
criteria each day.

&&

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

&&

$$

DISCUSSION.....MPC/Goodin
AVIATION.......Kieckbusch
FIRE WEATHER...MPC