Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 191145
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
545 AM CST Mon Feb 19 2018

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Tuesday
Issued at 411 AM CST Mon Feb 19 2018

Precipitation trends and type, snow and ice accumulations and
headlines are the main forecast concerns.

Have attempted to simplify headlines this morning, and just issued
winter weather advisories for the entire forecast area. Snow
accumulations are not expected to be significant due to a lack
of deep saturation, though Vilas county will likely pick up 1 to 3
inches today. Ice accumulations of a quarter to third of an inch
are anticipated across all but far north central WI, though these
accumulations are spread over a 30-36 hour period, which should
reduce the impacts to some degree. If localized heavier amounts
appear likely, an upgrade to a warning can be made.

A cold front was moving through north central WI early this
morning, but the coldest temperatures were observed ahead of it,
where winds have dropped off and skies have partially cleared.
Temperatures were still holding above freezing in the Fox Valley
and lakeshore areas. The front is expected to steadily shift
southeast this morning, and exit the forecast area by around
midday. Used a mix of several blended model data sets for
hourly temperatures, and this kept readings at or above freezing
in the Fox Valley and lakeshore areas until mid to late afternoon.
Precipitation should overspread the region during the late
morning and early afternoon as strong frontogenetic forcing
develops. Precipitation should be a mix of snow and freezing rain
far northwest, freezing rain from central into northeast WI, and
rain changing to freezing rain in the Fox Valley and lakeshore.
For the sake of simplicity, kept the starting time of the advisory
at 9 am for the northwest two-thirds of the CWA, and 3 pm in the
southeast, where temperatures will be slower to fall.

Models agree that precipitation should decrease across much of
the forecast area tonight, so pops and QPF have been reduced
accordingly. Even so, light freezing rain and freezing drizzle
will continue to produce some ice accumulations overnight.
On Tuesday, temperatures are forecast to warm above freezing
over the southeast half of the forecast area during the afternoon,
which could effectively end the icing there. Despite this
expectation, we kept a 00z/Wed expiration time in order to match
up with our neighbors. If the expected warming occurs, the
headlines may need to be canceled around midday southeast of a
line from Wautoma to Shawano to Crivitz.

.LONG TERM...Tuesday Night Through Sunday
Issued at 411 AM CST Mon Feb 19 2018

A persistent upper air pattern will shape up across North America
over the next week, with a deep trough settling over the western
conus, and ridging east of the Mississippi River.  This pattern
would place the western Great Lakes within southwest flow aloft,
which is more conducive for near to above normal temperatures, and
periods of precip.  Due to the upcoming winter storm, will just use
the multi-model blend for the forecast.

Tuesday night through Wednesday night...The cold front will finally
accelerate eastward on Tuesday night. Light precip consisting of
rain or freezing rain will likely be ongoing at the start of the
evening, then gradually come to an end from west to east through mid
evening. Any additional ice accums should be minor. Then Arctic high
pressure will build into the area during the overnight hours into
Wednesday. Skies will slowly clear during the time, which should
result in plenty of sunshine for Wednesday. As the high quickly
departs on late Wednesday night, may see some mid and high clouds
move in late, but no precip is expected at this time. Highs on
Wednesday falling to near normal.

Rest of the forecast...As weak isentropic lift returns, models are
more aggressive in bringing light precip to the area on Thursday
afternoon into Friday morning.  Temps look to be just cold enough
for snow, though wouldnt take much for some mixed precip to push
into central and east-central WI.  Could see an inch or two of snow
if temps remain below freezing.  After a brief period of dry
weather, another system looks to arrive next weekend, with
temperatures playing a critical role again in determining the precip
type.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 536 AM CST Mon Feb 19 2018

A cold front was sagging southeast through the area this morning.
Along and ahead of the front, patchy light fog was occurring. In
the colder air behind the front, MVFR/IFR ceilings were developing.
Precipitation is expected to fill in across the region during the
late morning and early afternoon, with a mix of snow and freezing
rain in north central WI, mainly freezing rain from central into
northeast WI, and rain changing to freezing rain in the east
central part of the state. Light freezing rain should taper off to
freezing drizzle this evening, though precipitation may pick up
again toward daybreak. Flight conditions should deteriorate to
IFR at most locations this afternoon, and continue through
tonight.

Gusty northeast winds will develop this afternoon in the Fox
Valley and lakeshore areas, with gusts to 30 mph possible. The
winds should subside this evening.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 3 PM this afternoon to 6 PM CST
Tuesday for WIZ038>040-045-048>050.

Winter Weather Advisory from 9 AM this morning to 6 PM CST
Tuesday for WIZ005-010>013-018>022-030-031-035>037-073-074.
&&

$$

SHORT TERM.....Kieckbusch
LONG TERM......MPC
AVIATION.......Kieckbusch



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