Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 300826
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
326 AM CDT FRI SEP 30 2016

Forecast discussion for routine morning forecast issuance

.SYNOPSIS...
Issued at 323 AM CDT Fri Sep 30 2016

More clouds and scattered showers today through Saturday,
especially in the east.

The large scale flow across the eastern Pacific is amplified, with
a ridge near the Gulf of Alaska and a trough off the west coast of
North America. From there, a much more zonal band of westerlies
extend across central Canada to the Atlantic. South of that, a
cut-off low is located over the Ohio Valley. The cut-off will be
the primary feature influencing the weather across the forecast
area the next few days as it drifts back north. Meanwhile back to
the west, the eastern Pacific trough will begin progressing
east, finally getting close enough to kick the cut-off out of the
area early next week.

The air mass currently across the area is of Canadian origin. But
it has been in place several days and has modified, and will
continue to do so as it lingers several more days. Clouds will
hold daytime temperatures to near or a little below normal today
and Saturday, especially in the east. Readings should then return
to above normal for the rest of the period. Precipitation chances
early in the period will be tied to the cut-off, then another
round of precipitation is likely during the middle to latter part
of next week when the western trough finally arrives in the area.
Those 2 events will likely result in amounts near or a little
below normal for the period.
&&

.SHORT TERM...Today...Tonight...and Saturday
Issued at 323 AM CDT Fri Sep 30 2016

The main short-term forecast issue is how to handle precipitation
associated with the northward return of the cut-off. The main
change in the guidance since yesterday has been to confine the
potential for rain primarily to eastern Wisconsin. It`s not yet
possible to resolve (in terms of the PoP forecast) individual rain
bands wrapping around the system, so simply structured forecast
with chance PoPs advancing northwest across east-central Wisconsin
today. The rain chance will expand farther northwest tonight,
remain in place Saturday morning, then begin to shift back off to
the east. It now appears the northwest corner of the forecast area
could get by with just a few sprinkles, or possibly even stay
completely dry.

Stayed fairly close to initialization grids based on a broad-
based blend of guidance products, though tweaked those some based
on expected cloud distribution and local effects.

.LONG TERM...Saturday Night Through Thursday
Issued at 323 AM CDT Fri Sep 30 2016

Precip chances this weekend, followed by timing of the next frontal
passage are the main forecast concerns in this portion of the
forecast.  A blend of the ecmwf/gfs will suffice.

Saturday night through Sunday night...Upper level low pressure will
be slowly drifting to the northeast over southern lower Michigan on
Saturday night into Sunday.  Should see widespread broken to
overcast conditions during this time as plenty of moisture will be
wrapping around the low.  Though scattered light showers will be
impacting eastern WI into early Sunday afternoon, central and north-
central WI should see isolated shower activity exit on Saturday
night. As the low finally moves away on Sunday night, then should
see some clearing arrive.  Max and min temps will remain seasonable.

Rest of the forecast...An amplified pattern will be in place across
the CONUS for much of the next work week.  As a result, the next
system will be slow to move eastward into the region. We should
therefore see dry conditions for Monday, Tuesday, and into the first
half of Wednesday at the same time as temps slowly warm a couple of
degrees each day.  A large cyclone will then push a front across the
region for the 2nd half of Wednesday into Thursday, bringing
widespread rain, and possibly some thunder.  Turning cooler and
breezy behind the system for Thu and Fri.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 323 AM CDT Fri Sep 30 2016

There will be some stratus over north-central Wisconsin early
today, and probably some lake-effect clouds with low bases in
east-central Wisconsin as well. Other than that, the main aviation
forecast concern is how quickly/how much to lower ceilings as
clouds with the cut-off continue to wrap back into the area. The
basic plan is to spread MVFR category ceilings northwest across
much of the area today, then lower the ceilings to IFR in east-
central Wisconsin tonight.
&&

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

$$

SYNOPSIS.......Skowronski
SHORT TERM.....Skowronski
LONG TERM......MPC
AVIATION.......Skowronski


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