Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 110821
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
321 AM CDT Wed Oct 11 2017

Forecast discussion for routine morning forecast issuance

.SHORT TERM...Today...Tonight...and Thursday
Issued at 321 AM CDT Wed Oct 11 2017

The region continues to be between systems with a Canadian high
pressure across the northern Great Lakes and a low pressure system
tracking through the northern Ohio Valley. While areas north of
highway 29 have remained dry with the high, areas to the south
have received various amounts of rain depending on how far south
they are. The better rain has been to the south closer to the
aforementioned low pressure system. Rain showers will continue
early this morning, then diminish through the morning as the low
moves to the east and high pressure re-establishes itself over the
western Great Lakes. However some light rain or drizzle may
remain early this afternoon as model soundings to the south show
moisture in the low levels while the hi-res models spit out light
amounts of QPF indicative of light rain or drizzle. Highs today
will generally be around 60 degrees.

Clouds will increase a bit from the west tonight as some showers
develop across the upper Mississippi Valley. While these showers
are expected to remain to the west, clouds are expected to stream
in from this activity. Overnight lows are expected to dip into the
40s. Thursday is expected to remain dry, however mostly cloudy
skies are expected as highs once again rise to around 60 degrees.

.LONG TERM...Thursday Night Through Tuesday
Issued at 321 AM CDT Wed Oct 11 2017

Models have now become into better agreement (namely the ECMWF)
with the timing of a surface low/cold front and trailing shortwave
trough this weekend. Overall, the amplified flow across the CONUS
at the start of the period flattens early next week behind the
departed trough and the removal of the subtropical upper ridge
over the southeast CONUS. After the weekend rain, the weather will
quiet down with temperatures generally at or above normal through
the extended forecast.

Northeast WI to remain under a southwest flow Thursday night,
gradually drawing more moisture into the region. A cold front is
forecast to move across the Upper MS Valley and reach far
northwest WI by 12z Friday. There is not much in the way of mid or
upper support initially, leaving the cold front and its lift as
the only way any precipitation would be generated. May leave a
slight chance late for north-central WI, but anticipate most of
the forecast area to be dry Thursday night. Min temperatures to be
mainly in the upper 40s to lower 50s, except middle 50s along Lake
MI. The cold front is forecast to continue slowly pushing east and
essentially bisect WI from near IMT-LSE by late Friday. The air
mass ahead of the front will continue to moisten as prevailing
south-southwest winds bring PW values into the 1.0 to 1.5 inch
range which is 1 to 2 standard deviation above normal for mid-
October. Do not see enough instability to carry thunder, so have
kept only showers in the forecast. Highest pops placed in the
vicinity of the front, thus likely pops for north/central WI
Friday afternoon with chance pops for east-central WI. Max
temperatures to range from the upper 50s to around 60 degrees
north-central WI, to the middle to upper 60s eastern WI.

The slow movement of the cold front means that this boundary will
not clear the forecast area until after midnight Friday night.
Showers would persist over all the region Friday evening with the
higher pops/QPF shifting into east-central WI. As the cold front
heads farther south and east during the overnight hours, look for
the showers to end over northern and most of central WI with a
decrease in clouds as drier air advects into WI from high pressure
to our north and west. Min temperatures to range from the upper
30s to around 40 degrees north-central, to around 50 degrees
across east-central WI. The cold front is still progged to stall
over extreme northern IL by Saturday morning and as low pressure
lifts northeast into the Midwest Saturday afternoon, this frontal
boundary will start to lift north as a warm front back into
southern WI by 00z Sunday. High pressure passing to our north
should keep enough of a dry push of air into northeast WI to keep
the morning hours dry. However, as the warm front approaches in
the afternoon and moisture begins to increase once again, shower
chances should also increase from south to north, reaching
central/east-central WI. This band of showers to also be aided by
the right entrance region of a strong 150 knot jet situated over
Ontario. Lastly, stronger instability to remain to our south near
the warm front, thus no thunder wording in the forecast.

Saturday night looks to be a soggy night as the surface low tracks
northeast across southern WI into northern/central Lower MI. Gusty
northeast winds and gradual onset of CAA will make it feel raw
outdoors, along with locally heavy rain in the deformation zone
which would be more across central/east-central WI. PW values
climb to around 1.5 inches, thus some 1+ inches of rain is
possible. Shower chances would then linger through at least Sunday
morning as the trailing shortwave trough swings through WI,
although most of the models continue the precipitation chances
pretty much through the daylight hours. Sunday also looks to be
the coolest day of the long-term with max temperatures only in the
upper 40s to lower 50s north-central, upper 50s east-central WI.

The mean flow is expected to transition to more of a zonal
configuration for the start of the work week with an area of high
pressure to dominate northeast WI weather through Tuesday. The
core of this high pressure is to our south, thus there may be too
much of a pressure gradient over WI to bring any kind of a frost
threat to central or east-central WI Monday night. Otherwise, look
for mostly sunny days Monday and Tuesday with temperatures
warming to above normal levels on Tuesday as winds back to the
west-southwest.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1021 PM CDT Tue Oct 10 2017

VFR conditions should prevail through Wednesday afternoon despite
rain across portions of central and east-central Wisconsin into
Wednesday morning. The rain is still expected to stay south of a
KAUW to KSUE line. The rain will gradually shift to the southeast
and end overnight or early Wednesday morning as low pressure
moves away from the area. Gusty east/northeast winds can be
expected across east-central Wisconsin for the overnight hours,
and across the entire area on Wednesday.
&&

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

$$

SHORT TERM.....Kurimski
LONG TERM......AK
AVIATION.......Eckberg



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