Forecast Discussion for GRB NWS Office
FXUS63 KGRB 170422

Area Forecast Discussion
National Weather Service Green Bay WI
1022 PM CST Fri Nov 16 2018

Updated aviation portion for 06Z TAF issuance
and new information added to update section

Issued at 1022 PM CST Fri Nov 16 2018

The snow associated with the low pressure currently passing to the
south appears to be trending further south. This is supported by
doppler radar imagery as well as the recent hi-res model runs.
Therefore will scale back POPs and snowfall amounts across the
southern cwa during the overnight hours. Overall not much, if any,
snow is expected during the overnight hours across central and
east-central Wisconsin. The best chance will be further south
across Waushara, Winnebago, and Manitowoc counties. However even
these areas do not look like a great chance to see much snow.


.SHORT TERM...Tonight and Saturday
Issued at 315 PM CST Fri Nov 16 2018

The main forecast concern is snowfall trends and totals with
the system approaching from the northern plains.

Models have trended south with the low pressure system and lower
with the associated QPF/snowfall that will impact the region in
the late evening and overnight hours, then exit early Saturday.
The snow will mainly impact our southern two tiers of counties
(central and east central WI), with the highest totals (1 to 1.5
inches) occurring over southern Wood, Waushara, Winnebago,
Calumet and Manitowoc counties.

A second are of snowfall will occur over Vilas county and far
north central WI due to lake-effect. Lake-H8 delta-t`s will
increase to 20+ C as CAA occurs tonight, and winds will turn
to a favorable NNW trajectory. Have increased pops to likely
over northwest Vilas county, and bumped snowfall accumulations
to around 2 inches there. The lake-effect should taper off
Saturday afternoon as Canadian high pressure pushes into
the region.

Lows tonight are expected to drop into the upper teens to upper
20s. Highs on Saturday will range from the 20s northwest to the
lower 30s southeast.

.LONG TERM...Saturday Night Through Friday
Issued at 315 PM CST Fri Nov 16 2018

The main concerns for this forecast period are the chances for
precipitation for Monday and Tuesday. Below normal temperatures
will also continue through Tuesday.

A surface high pressure system positioned over the Central Plains
tracks to the southeast during the start of this period, allowing
for the transition to a northwest upper-level flow on Sunday. As
the high pressure continues to track further southeast on Sunday
night, a surface clipper system begins to move southeast across
the Dakotas. This clipper system poses as the next precipitation
maker for Wisconsin into Monday morning. There is much uncertainty
with the track of this system amongst the models, as well as the
amount of moisture associated with it. Due to this uncertainty,
kept a blend of the model guidance chance pops of snow showers
across the majority of the forecast area ending Monday afternoon.

Once the clipper system exits to the east Monday evening, a weak
area of surface high pressure tries to move into the Upper
Mississippi Valley. The ECMWF and the Canadian indicate another
quick moving clipper system will pass over Lake Superior,
bringing a small chance for some precipitation across far
north-central Wisconsin Tuesday evening. The GFS does not
indicate this clipper system will impact the area and stay further
north. Therefore, kept small chances for precipitation across far
north-central Wisconsin.

An area of high pressure will then position itself over Ontario,
as the clipper system exits to the east on Wednesday, resulting in
dry conditions through Thanksgiving. This pattern will also
allow for warmer air to push into the area on Wednesday and
Thanksgiving, bringing high temperatures back to normal.

.AVIATION...for 06Z TAF Issuance
Issued at 1022 PM CST Fri Nov 16 2018

Widespread MVFR ceilings covered most of the TAF sites tonight,
with a few spots just above 3k ft across east-central Wisconsin.
These conditions should hold until midday on Saturday when drier
air works its way in from the west with skies clearing out by
Saturday evening.

The area of snow to the southwest now looks to stay south of all
of the TAF sites overnight into Saturday morning, therefore will
remove snow from the TAF sites with this issuance.



SHORT TERM.....Kieckbusch
LONG TERM......Hykin

NWS GRB Office Area Forecast Discussion