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000
FXUS63 KGRB 212342
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
642 PM CDT Sun Apr 21 2024

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Elevated fire weather conditions are expected Monday afternoon
  due to relative humidities ranging from 20 to 30 percent and
  southwest winds of 15 to 20 mph with gusts to 30 mph.

- Precipitation chances return Monday evening through Tuesday. A
  few thunderstorms are possible Tuesday afternoon, but severe
  weather is not expected.

&&

.DISCUSSION...
Issued at 249 PM CDT Sun Apr 21 2024

Short Term...Tonight and Monday

Sunny skies allowed temperatures to warm steadily through the
morning hours, allowing us to hit our convective temperatures in
the 50s for much of the region. The resulting fair weather cumulus
field will likely stick around in the region through the early
evening, before steadily dissipating for the overnight. Similarly,
the deep mixing in the region will keep wind gusts around 20 to 25
mph and low relative humidity in the region for around the same
timeframe.

Tonight, winds will begin to slacken and skies should largely be
clear. This will provide another ideal night for steady
radiational cooling. Kept temperatures fairly cool for the
overnight period, especially in the typical cool spots near the
Upper Peninsula border and in portions of the northwoods where
Monday morning low temperatures may be in the lower to middle 20s.
Areas closer to the Fox Valley and lakeshore will likely remain in
the lower 30s overnight.

Monday, winds will switch over to the southwest as a low pressure
system approaches southern Manitoba. The tightening pressure
gradient will help give winds a boost as a result, with some gusts
up to 25 to 30 mph in the afternoon. The strong southwest flow
will also bring in some warmer temperatures, with most of the area
expected to get into the 60s tomorrow afternoon. That said, little
additional moisture will advect into the region, so relative
humidity readings in the afternoon will again be fairly low, so
elevated fire weather conditions are expected again for Monday
afternoon. Finally, a cold front will approached the region as the
aforementioned low pressure system passes by to our north. This
could bring some scattered showers into central Wisconsin by
Monday evening. Given the relatively scarce moisture however,
would expect any showers to be fairly light.

Long Term...Monday Night Through Sunday

A cold front will bring showers as it moves across the region
Monday night. An upper level disturbance and reinforcing push of
colder air will produce showers and isolated thunderstorms
Tuesday. The rain showers could mix with or change to snow across
the far north Tuesday afternoon, but no accumulation is expected.

A 1030 mb surface high will drop south from James Bay Tuesday night
and Wednesday and bring drier and colder air into the area. The
air will be very dry Wednesday afternoon, with precipitable water
values of .15 inches. This will make for relative humidities of 20
to 30 percent, but cool temperatures and light winds should lessen
fire threats to some degree.

Temperatures will warm Thursday and Friday as the surface high moves
off to New England and winds become southerly. SHowers and thunderstorms
are likely Friday afternoon and night if the medium range models are
correct. They have a surface low moving across the Plains, with a
decent supply of moisture advecting north.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 635 PM CDT Sun Apr 21 2024

VFR flight conditions are expected through the TAF period. High-
based cumulus louds will continue to erode early this evening,
followed by mostly clear skies overnight into early Monday. Clouds
will increase ahead of a frontal system Monday afternoon, with
showers arriving at the western TAF sites near the end of the TAF
period.

Light winds are expected tonight, but southwest winds will
increase to 15 to 20 knots with gusts to around 25 knots during
the late morning and afternoon.
&&

.FIRE WEATHER...
Issued at 249 PM CDT Sun Apr 21 2024

Monday may be of higher concern, fire weather-wise, than today.
Winds will be slightly stronger in the afternoon, sustained around
15 to 20 mph with gusts up to 30 mph; while minimum relative
humidity readings will be similar to today, around 20 to 30
percent.

Another period of elevated fire weather conditions is possible
Wednesday and Thursday, as a dry airmass moves into the region.
However, winds will be below critical levels due to the proximity
of a prevailing high pressure system.

&&

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

&&

$$

DISCUSSION.....Uhlmann/RDM
AVIATION.......Kieckbusch
FIRE WEATHER...Kieckbusch