Area Forecast Discussion
Issued by NWS Green Bay, WI

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050
FXUS63 KGRB 192137
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
337 PM CST Fri Jan 19 2018

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Saturday
Issued at 337 PM CST Fri Jan 19 2018

Tranquil winter weather day in progress across the area with temps
10-15 degrees above normal. Mid-upper level clouds pushed across
the area providing for fair skies.

The quiet weather will continue tonight as the region resides in a
zonal flow pattern and no surface features or sufficient moisture
to produce precip. Strong 150+ knot upper jet over southern Canada
along with moisture above 10,000 ft will keep mid-upper level
clouds across the area. SW/W surface winds will help keep temps
well above normal tonight, with most spots only falling into the
20s to around 30 degrees. The light winds in combination with
slightly higher dewpoints and melting snow could lead to patchy
fog development.

Not much change on Saturday, with the upper jet slowly moving
east. Weak gradient will allow winds to be very light. Mid-upper
level clouds are again expected, which will limit heating somewhat
and provide for fair skies. Temps will run 10 to 15 degrees above
normal for most spots.

.LONG TERM...Saturday Night Through Friday
Issued at 337 PM CST Fri Jan 19 2018

The upcoming winter storm system is the primary concern during
this part of the forecast.

A mid level trough is forecast to move onshore, reaching the
western CONUS, tonight. A cutoff 500 mb low will then develop and
cross the Plains, approaching the Great Lakes region late this
weekend/early next week.

Onset of the main round of precipitation looks to be Sunday
evening, with PoPs then increasing during the day on Monday and
gradually decreasing Monday night before the storm pushes away
from the area on Tuesday.

The 12Z models have generally been showing the surface and 500 mb
lows passing a little farther south than they had on previous
runs. The ECMWF was still the farthest south and slowest of the
NAM/GFS/ECMWF/Canadian. Precipitation type issues remain due to
model differences with the exact path of the surface and mid level
cyclones.

The blended model solution showed quite a bit of ice accumulation
with some locations in central Wisconsin with just a little less
than a quarter inch. Heaviest snowfall was in far north central
Wisconsin. Ended up adjusting some of the forecast grids to yield
less ice and pushed the axis of heaviest snowfall a little farther
southeast. Confidence in exact precipitation type and totals at
any location is low due to model differences, so have decided to
hold off issuing any headlines but there should be some pretty
high snowfall totals over some part of the area by the time this
event is finished.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1144 AM CST Fri Jan 19 2018

VFR conditions expected through Saturday, as mid-upper level
clouds continue to push across the region. Some models showing low
cloud/fog development tonight, but those models have been over-
doing low-level moisture, so will not include any low clouds or
fog. Increasing low level moisture arrives Saturday night and
Sunday, so there is a better chance of lower clouds and possible
fog then.

Low level wind shear is expected through late this evening as
west/southwest winds of 35 to 45 knots at 2000 ft with southwest
winds at the surface around 10 knots.
&&

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

$$

SHORT TERM.....Bersch
LONG TERM......MG
AVIATION.......Bersch



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