Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 242332
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
632 PM CDT Mon Apr 24 2017

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Tuesday
Issued at 255 PM CDT Mon Apr 24 2017

The latest rap analysis and satellite/radar imagery show a surface
warm front losing definition over central Wisconsin early this
afternoon.  Despite a influx of dry air above the inversion and
increasing south winds aloft, relative humidity values have been
behaving so far, with only a few locations over north-central WI
below 25 percent. Will still have a few hours to tap into the vast
reservoir of dry air above the inversion, but southeast winds will
likely prevent that from happening over eastern WI. Looking to the
west, a cold front is traveling east over the eastern Dakotas, while
a shortwave is producing showers from eastern Nebraska into southern
Minnesota. Forecast concerns revolve around precip chances as
moisture pushes in ahead of the cold front and shortwave trough.

Tonight...As a shortwave trough swings northeast across the region,
a cold front will slowly slide into the northern Mississippi Valley.
Southerly flow aloft and southeast winds at the surface will provide
a steady influx of dry air below 10 kft which should hold off
precip.  Could be some virga though over north-central WI as the
shortwave moves through.  Otherwise the combo of mid and high clouds
overhead and a breezy southeast wind should keep temperatures mild.
Went slightly above the multi-model blend with low temps mainly in
the middle to upper 40s.

Tuesday...The cold front will not make much progress eastward, but
will see a weak shortwave impulse move across the state during the
afternoon.  This shortwave will have more moisture to work with than
the impulse arriving tonight, so will see the first decent chance of
showers over central and north-central WI, mainly during the middle
to late afternoon hours.  Eastern WI should remain protected by
lingering dry air.  Otherwise, should see periods filtered sunshine
and broken cloud cover through the day. Temps warming into the
middle 60s to near 70 degrees.

.LONG TERM...Tuesday Night Through Monday
Issued at 255 PM CDT Mon Apr 24 2017

Southwest upper flow and lots of upper jet action
will provide at least a few periods of significant precipitation
this week. It will also turn much cooler with some chance of
winter precipitation across northcentral Wisconsin late Wednesday
night and Thursday, and again possibly Saturday.

The first round of precipitation will begin Tuesday afternoon or
evening and continue into Thursday as upper troughs approach from
the northern and southern Plains. They will combine to produce
surface lows that track northeast along a nearly stationary front
from Oklahoma to Lake Michigan. As colder air arrives late
Wednesday night the rain may change to freezing rain or sleet in
the far north. WHile not a climatologically favorable time of the
year for freezing rain, forecast soundings support it as the most
likely precipitation type if the temperatures aloft are as
forecast.

Another synoptic scale weather system with possible significant
precipitation will arrive at the end of the week. A 1032mb surface
high is forecast to be north of the Great lakes, which could
deliver enough cold air in the low levels to produce some winter
precipitation in the far north, depending on the track and timing
of course.

Rains from these systems will likely cause rivers and streams to
rise again later this week, with possible minor flooding i some
areas.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 628 PM CDT Mon Apr 24 2017

LLWS is expected to develop this evening, as surface winds
decrease and winds aloft increase to around 40 kts. The LLWS
should subside toward daybreak. Otherwise, broken mid-level
clouds and patchy virga can be expected through Tuesday morning.

A cold front will approach the region Tuesday afternoon, and
bring rain showers and lowering ceilings.

&&

.FIRE WEATHER...
Issued at 255 PM CDT Mon Apr 24 2017

As a cold front lifts back north as a warm front across the
western Great Lakes today, warmer temperatures will return along
with gusty southeast winds and low relative humidities. Near
critical fire weather conditions are possible this afternoon as
temperatures rise into the 60s, winds gust to 20 to 30 mph, and
relative humidities bottom out in the 20s. A low pressure system
arriving from the west will bring relief on Tuesday as relative
humidities rise to around 50 with rain showers.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM.....MPC
LONG TERM......RDM
AVIATION.......Kieckbusch
FIRE WEATHER...MPC



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