Area Forecast Discussion
Issued by NWS Green Bay, WI

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942
FXUS63 KGRB 141752
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1152 AM CST Tue Nov 14 2017

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Wednesday
Issued at 323 AM CST Tue Nov 14 2017

Low level moisture continues to increase across the region early
this morning, as noted by the low ceilings and some fog across
northeast Wisconsin. Some low level isentropic lift will take
advantage of this low level moisture, leading to drizzle and
freezing drizzle this morning before transitioning to all drizzle
as surface temperatures warm to above freezing. The mesoscale
models seem to have a fairly good handle on the drizzle, with
upstream ground truth of drizzle across western Wisconsin leading
to the increased confidence in this portion of the forecast. The
main areas of concern for freezing drizzle will be across central
and north-central Wisconsin. The freezing drizzle could make the
morning commute slippery, especially on overpasses and bridges.
Despite this a Winter Weather Advisory is not anticipated as the
drizzle is fairly spotty upstream and not persistent for any
length of time. Highs today under cloudy skies will generally be
in the upper 30s to lower 40s.

The drizzle will transition to rain tonight as deeper moisture and
better lift arrive as a low pressure system tracks towards the
western Great Lakes. This will likely bring a widespread light to
moderate rain to the area tonight as lows only fall into the
middle to upper 30s, keeping the precipitation type as all rain.

The low will bring a cold front through late tonight and early
Wednesday, however the push of cold air will not be felt until a
secondary cold front pushes through Wednesday afternoon. This will
cause afternoon temperatures to fall as 850 mb temperatures fall
10 degrees from the morning to the afternoon. Lingering morning
rain will end for much of the area, however wrap around moisture
and a feed off Lake Superior will keep precipitation chances in
across much of north-central Wisconsin during the afternoon hours.
The push of cold air will transition the rain to snow across the
far north late in the afternoon. Given the late transition
snowfall amounts are expected to be light across the far north on
Wednesday afternoon. Daytime highs on Wednesday will likely be
earlier in the day before the secondary cold front pushes through,
with readings ranging from the upper 30s across the north, with
middle 40s across east- central and northeast Wisconsin.

.LONG TERM...Wednesday Night Through Monday
Issued at 323 AM CST Tue Nov 14 2017

Active pattern expected during the period as several issues to
deal with. Beginning with Wednesday night, day shift increased
snow chances Wednesday night and increased them even more across
Vilas county as winds turn to a very favorable direction with lake
to 850mb temperature differences around 14 C noted. Since it is a
short duration of favorable fetch/wind speeds, still think 1 to 2
inches across northwest Vilas county should suffice for now.

Tranquil conditions expected Thursday as high pressure slides
eastward across the area. The tranquil weather should linger into
Thursday evening as the next system approaches from the west.
After midnight, precipitation type issues develop across northern
Wisconsin as strong southerly flow and 850mb warm advection noted.
The 850mb zero celsius line pushes northward into northern
Wisconsin. Also, do expect air temperatures to rise slowly
through the night. Expecting rain across the Fox Valley and
lakeshore. To the north and west of the Fox Valley, precipitation
could fall in the form of freezing rain, sleet or snow. To early
to determine the exact precipitation type, but will mention
hazardous travel in the Hazardous Weather Outlook (HWO). Any mixed
precipitation across the north should change over to all rain by
late Friday morning. The precipitation is expected to change back
to snow Friday night and temperatures fall to near the freezing
mark across the north. Precipitation should be mainly rain
elsewhere, although some differences noted in how quick the cold
air makes it into our southern counties. Windy/blustery conditions
expected throughout much of the upcoming weekend as colder air
returns to the area.

One note, there is some differences in the wind trajectory across
the north over the weekend that could impact lake effect snow
totals across far northern Wisconsin. Wind component may be too
westerly at times for any significant snow accumulations. Will
continue to monitor if the models turn winds more northwesterly.
Great deal of uncertainty in the Monday forecast for now, thus
will not make any significant changes to this period.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1152 AM CST Tue Nov 14 2017

IFR conditions prevailed across most of the area at 17Z, with the
exception of eastern and parts of central Wisconsin where it was
MVFR or VFR at most locations. A downward trend in ceilings was
already occurring late this morning, so expect IFR conditions to
spread across the rest of the area as low level moisture
increases. ARX and MPX radars appeared to be indicating some
drizzle that was moving toward/into the forecast area at midday,
so would expect drizzle in advance of rain that is forecast to
move in later this afternoon/tonight in continued warm advection
ahead of an approaching surface system and mid level short wave.
Do not expect improvement until during the day on Wednesday when
ceilings and visibility increase as rain ends with the departure
of the surface system and upper dynamics.
&&

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

$$

SHORT TERM.....Kurimski
LONG TERM......Eckberg
AVIATION.......MG



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