Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 220816
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
316 AM CDT Sun Apr 22 2018

Forecast discussion for routine morning forecast issuance

.SHORT TERM...Today...Tonight...and Monday
Issued at 315 AM CDT Sun Apr 22 2018

Upper ridging across the region today through Monday combined
with a surface high pressure area anchored over the state will
continue to produce quiet, mild and dry conditions.

Expected plenty of sunshine today as a one weather system
continues to slide southeastward into the southeast states. Some
mid to high level clouds may be on the increase from the
northwest on Monday as a weak northern plains frontal system
approaches from the northwest.

Will go with persistence for temperature and dew point trends.
Dew points have been crashing into the single digits and teens
the last several days despite the ongoing snowmelt.

Developing light east winds will likely produce cooler readings
along the lakeshore and Bay each today and Monday.

.LONG TERM...Monday Night Through Saturday
Issued at 315 AM CDT Sun Apr 22 2018

Models have come into better agreement with the handling of the
major weather features this week. A closed upper low will meander
over the eastern Pacific until late in the week when it hits the
northern CA coast. An upper ridge is forecast to reside over the
western CONUS before shifting into the Rockies. A broad upper
trough is expected to set up over east-central NOAM. For northeast
WI, precipitation chances would be relegated to Tuesday afternoon/
night as a cold front/part of a shortwave trough push across the
area and again late in the week as the main upper trough develops
overhead. Temperatures are forecast bounce around and pretty much
end up averaging close to normal. The snowpack will continue to
diminish, leading to several area rivers to surpass bankfull stage
with a couple reaching flood stage.

The system to our south will be moving through the TN Valley
Monday night and the northern fringe of its cloud shield may
brush east-central WI. Meanwhile, a cold front is forecast to push
into northwest WI by 12Z Tuesday. Models are consistent in
showing any precipitation to be post-frontal in the vicinity of a
shortwave trough over the Upper MS Valley/northern and central
Plains. Therefore, anticipate partly cloudy skies with light/
variable winds. Min temperatures will generally end up in the
35-40 degree range over most of northeast WI.

The cold front pushes across the rest of WI on Tuesday, but
precipitation chances to be tied to the trailing shortwave trough.
The GFS stands alone in bringing a chance of rain showers to
northeast WI. The NAM, GEM and ECMWF split the trough into two
with the northern section moving across northeast sections of the
Great Lakes and the southern section of the trough to sag
southeast across the central Plains. Furthermore, the GFS may be
bringing too much moisture into WI, considering the gulf is cut-
off. Max temperatures to range from the middle to upper 50s
north-central WI/near Lake MI, lower to middle 60s elsewhere.

A token small pop will be carried over into Tuesday evening,
mainly over eastern WI as the GFS has the shortwave trough start
to exit the area. Otherwise, models indicate partly cloudy skies
with cooler air spilling back into the region behind the departed
cold front. Look for min temperatures to range from the upper 20s
to around 30 degrees north-central, to the middle 30s east-central
WI. A ridge of high pressure is then forecast to slide into the
western Great Lakes on Wednesday which should allow skies to be
mostly sunny. However, temperatures will be held in check by
north-northeast winds. Look for readings to reach the middle to
upper 40s near Lake MI, lower to middle 50s for inland locations.

The surface ridge shifts to the east Wednesday night and attention
turns to the next cold front/shortwave trough that moves across
the northern Plains into the Upper MS Valley. The speed of this
system differs a bit among the models with the ECMWF about 6-9
hours slower than either the GFS or GEM. This becomes apparent by
Thursday as the ECMWF barely gets any rain to central WI, while
the GFS has the leading edge of rain already in Lower MI. Due to
the wide range of possibilities (and the likelihood the models
will ultimately adjust their timing), will bring chance pops to
central WI in the morning and over the entire forecast area
Thursday afternoon. Max temperatures to be in the lower to middle
50s north-central/near Lake MI, middle to upper 50s elsewhere.

As cooler air filters into the region behind the cold front,
expect any rain to mix with or changeover to snow Thursday night.
The mixed precipitation could even linger into Friday morning
before finally pulling away by Friday afternoon. Temperatures are
forecast to fall below normal between the cyclonic flow and CAA.
Look for max temperatures to only reach the middle to upper 40s
north-central/near Lake MI, upper 40s to lower 50s for other
locations.

Another ridge of high pressure will push into the Great Lakes to
end the week, so anticipate dry conditions for Friday night and
Saturday. Winds backing to the west and the onset of WAA should
allow temperatures to moderate on Saturday. Look for max
temperatures to be around 50 degrees near Lake MI, lower to middle
50s north-central and middle to upper 50s elsewhere.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1041 PM CDT Sat Apr 21 2018

Some SCT-BKN cirrus clouds will track through the southern TAF
sites during the overnight hours. Further north clear to mostly
clear skies will prevail. VFR conditions will prevail over all of
the TAF sites through the period with light winds. The very dry
airmass in place has thus far prevented fog development during the
overnight hours, therefore there are no plans to put it in with
this set of TAFs.
&&

.HYDROLOGY...
Issued at 315 AM 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 have already risen above bankfull and more are likely over
the next couple of days. The Wolf River is projected to reach flood
stage at Shiocton Monday night and a river flood warning will be
issued. 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.....TDH
LONG TERM......Kallas
AVIATION.......Kurimski
HYDROLOGY......Kallas



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