Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 171724
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1124 AM CST Tue Jan 17 2017

Updated aviation portion for 18Z TAF issuance

.UPDATE...
Issued at 640 AM CST Tue Jan 17 2017

Radar shows accumulating ice has overall ended over central
Wisconsin early this morning. However freezing drizzle with
spotty freezing rain continues to linger. Secondary roads,
parking lots and sidewalks likely have a good coating of ice and
will continue to produce hazardous driving conditions. Will
update to remove the warning and head into an advisory for the
rest of the morning hours.
&&

.SHORT TERM...Today...Tonight...and Wednesday
Issued at 233 AM CST Tue Jan 17 2017

Wintry mix continues this morning. Check of power outages show a
few over central Wisconsin early this morning where reports of
more ice accumulation. Move to winter storm warning last evening
working out well. Band of deformation region of precipitation
moving into northern Wisconsin producing mainly light snow as per
observations. Still anticipate a mix reaching North Central
Wisconsin early this morning where no headline is in effect, but
will continue with a SPS. For the rest of the region, will
continue with the advisory as roads remain slick, with very
slippery conditions on area sidewalks and parking lots.

Even as the dry slot works into central Wisconsin, freezing rain
may turn to freezing drizzle to continue support of headlines this
morning. Will take a another look at any headline adjustments just
before daybreak.

Eventually the precipitation and mainly rain this afternoon will
taper off from west to east as the surface low over Northeast
Illinois this morning works into lower Michigan today.

Forecast challenge tonight then turns to cloud trend or clearing
trend. A few models hang onto the stratus longer this evening,
while other models suggests a bit faster clearing. Faster clearing
would support more fog along with a quicker refreeze of the wet
roads.

Quiet weather for tonight into Wednesday with a high pressure
ridge drifting over. Developing southwest winds Wednesday will
begin a mild trend this week.

.LONG TERM...Wednesday Night Through Monday
Issued at 233 AM CST Tue Jan 17 2017

The latest GFS ensemble mean indicates that split flow will be the
predominate pattern across North America during this period.  A
large trough will be present over the west coast for much of this
time, and several shortwaves will eject out of this trough before
lifting northeast towards the Great Lakes.  However, each one will
run into a rather beefy mid-level ridge, that will cause the
shortwaves to weaken prior to moving into the region.  The ecmwf
compares well to the ensemble means, so will put more stock into its
solution.

Wednesday night through Thursday night...Mainly quiet during this
period as the region will reside between the westerlies to the
north, and an upper level low slowly moving northeast over the
central Plains.  As is fairly typical in a split flow pattern, not
much cold air out there, so will see temps above normal, with mainly
mostly clear conditions.  Could see clouds increase late Thursday
night ahead of the upper low.  Highs in the upper 30s to lower 40s
on Thursday, and lows mainly in the 20s to around 30.

Rest of the forecast...Despite its relatively close proximity on
Friday (southern Great Lakes), the upper low will be running into a
blocking ridge and weakening at the same time.  Though precip
chances look low, chances are relatively higher for central and east-
central WI for Friday. A few spotty showers could move into the area
this weekend, but better chances look farther west towards the
northern Mississippi Valley. Then another upper low will be shifting
east towards the Ohio Valley early next week.  The gfs is farther
north with this system, so changes in the track appear likely.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1123 AM CST Tue Jan 17 2017

Even as the area of low pressure continues to move away from the
region, visible satellite imagery shows plenty of clouds left over
Wisconsin. Lowest cigs/vsbys (mainly IFR category) exist across
central/east-central Wisconsin due to more mixed precipitation
that fell overnight. These low clouds are expected to stick around
this afternoon into tonight and could even linger a few hours into
Wednesday. Northern Wisconsin could actually see some sunshine
this afternoon with mainly VFR conditions, although patchy MVFR
cigs are possible at times. Much better flying conditions are
expected on Wednesday as a weak ridge of high pressure moves into
the region.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until noon CST today for WIZ013-018>022-
030-031-035>040-045-048>050-073-074.
&&

$$

UPDATE.........TDH
SHORT TERM.....TDH
LONG TERM......MPC
AVIATION.......AK


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