Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 222253
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
553 PM CDT Sun Apr 22 2018

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Monday
Issued at 231 PM CDT Sun Apr 22 2018

The latest RAP analysis and satellite/radar imagery show a large
area of high pressure stretching from the east coast to the
northern Mississippi Valley early this afternoon. Split flow
continues to dominate the upper air pattern across the central
NOAM, with a storm system over the south-central part of the
country and another over central Canada. Between these systems,
skies remain mostly clear except for some thin, wispy cirrus
shifting into central WI on the far northern edge of the system
further south. With systems continuing to split north and south of
the state, the main forecast concerns revolve around temps and
humidities.

Quiet weather will continue across the region through Monday
afternoon thanks to high pressure. Some cirrus from the storm
system to the south will likely get caught up in the westerlies
and invade the region later tonight into Monday. Although some
moistening will occur, very dry air will remain below 500mb, so
any thin cirrus should not have much impact on temps. Still no
sign of fog during the overnight hours, despite all of the melting
take place. Will continue to keep fog out of the forecast.
Temperatures will continue their warming trend, with lows in the
20s and 30s tonight, and in the upper 50s to mid 60s on Monday.
Readings will be cooler near Lake Michigan due to light onshore
flow. Dropped humidities across far northern WI again tomorrow
afternoon based on trends over the past few days, and little
change to the airmass in place.

.LONG TERM...Monday Night Through Sunday
Issued at 231 PM CDT Sun Apr 22 2018

The highlights from the long term are the warmer temperatures
continuing to chip away at the snowpack, a shortwave trough/cold
front moving into the area on Tuesday afternoon, and the passing
of another shortwave trough/cold front for Thursday into Friday.

A split flow pattern remains over the area for the start of the
long term with zonal flow to the north of Wisconsin and a low
pressure system sitting over the Tennessee Valley. This flow will
change heading into Tuesday morning with the approaching shortwave
trough/cold front. Model guidance is in agreement with the timing
for the cold front passing over Wisconsin Tuesday afternoon. This
will keep high temperatures for Tuesday close to and slightly
above normal ahead of the frontal passage. The uncertainty of this
system remains with how much post-frontal precipitation is
generated. Compared to yesterday, the GFS has backed off with
precipitation and the Canadian added some in for Tuesday evening.
Kept slight chance pops in for Tuesday afternoon over central and
far northeast Wisconsin.

Conditions for Wednesday will remain dry and slightly cooler with
temperatures closer normal before the next shortwave trough/cold
front arrives. The models are still not in agreement with timing
of this shortwave trough/cold front. Due to the disagreement, a
blend of the GFS and ECMWF was favored for the timing of the
frontal passage. In doing so, the best chance for precipitation
would be during Thursday afternoon and Thursday night behind the
cold front. With the cooler air filling in behind the front, it
is possible for any rain to mix with or change completely over to
snow Thursday night into Friday morning. At this time, any
accumulations look quite minor.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 553 PM CDT Sun Apr 22 2018

VFR conditions with light winds will prevail through the TAF
period. The very dry airmass in place continues to prevent fog
development during the overnight hours.
&&

.HYDROLOGY...
Issued at 231 PM CDT Sun Apr 22 2018

Warming temperatures will continue to produce melting of the
current snowpack over northeast WI. This will lead to additional
runoff and the steady rise of area rivers and streams. Several
rivers are expected to surpass bankfull and more are likely over
the next couple of days. The Oconto River near Oconto is forecast
to reach flood stage Monday morning and the Wolf River is
projected to reach flood stage at Shiocton Monday afternoon.
People living near rivers and streams should keep a close eye on
the anticipated river rises and keep up to date on the latest
river forecasts.
&&

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

$$

SHORT TERM.....MPC
LONG TERM......Hykin
AVIATION.......Kurimski
HYDROLOGY......Hykin



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