Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 141736
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1136 AM CST Wed Feb 14 2018

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Thursday
Issued at 330 AM CST Wed Feb 14 2018

Temperatures, cloud trends and minor precipitation chances on
Thursday, are the main forecast concerns.

Satellite indicated a small but persistent area of low stratus
over north central WI early this morning. Winds stayed up enough
to hold temperatures in the upper teens to middle 20s in most
locations, but winds decoupled in a few spots in central WI,
allowing temperatures to drop into the single digits and lower
teens.

Models suggest that the low-level humidity will mix out over
north central WI this morning, resulting in mostly sunny skies
across the forecast area. The sunshine, combined with southwest to
west winds, should allow temperatures to warm into the upper 30s
to lower 40s in most locations, with a few middle 40s in the
typical warm spots.

Expect low clouds to reform northwest of a line from Wausau to
Iron Mountain tonight. Precipitation chances are slim to none,
as moisture is shallow (at or below 900 mb), with no lift in the
moist layer. Lows will be quite mild, with readings in the middle
20s northwest to the upper 20s and lower 30s southeast.

On Thursday, a cold front will shift south through the the area
during the day. Low-level moisture may deepen enough for patchy
freezing drizzle over far north central WI in the morning.
Deeper saturation occurs later in the day, especially in the far
northwest and far southeast, where chance POPs are warranted.
Forcing will be provided by mid-level frontogenesis and the LFQ of
an upper level jet. Lake-effect will also play a role in far
north central WI as cold north-northwest winds flow across western
Lake Superior.

.LONG TERM...Thursday Night Through Tuesday
Issued at 330 AM CST Wed Feb 14 2018

Forecast concerns mainly revolve around precip chances, first on
Thursday night, then over the weekend.  In general, the weather
pattern is expected to turn more active as the upper flow turns to
the southwest late in the weekend into early next week.

Thursday night through Friday night...A cold front will be sliding
southeast across the southern Great Lakes and into the Ohio Valley
on Thursday night.  But behind the front, the arrival of shortwave
troughing combined with modest mid-level fgen remains on track to
produce light snowfall.  Most of the snow should fall during the
evening, with around a half inch possible for most locations.
Isolated spots may see up to an inch.  As the light snowfall winds
down late Thu night, Arctic air will be surging into the area with a
brisk northwest wind.  Wind chills will be falling to around 15
below over far northern WI by early Fri morning, but not quite cold
enough for a wind chill advisory.  Otherwise, high pressure will be
moving across the region on Friday, yielding plenty of sunshine, but
with below normal temps. Clouds will then be increasing late Friday
night ahead of the next shortwave, but too much dry air in the low
levels for precip.

Rest of the forecast...The next shortwave will be moving across the
region on Saturday.  Models are more ambitious in generating light
precip, partly due to steep mid-level lapse rates within the trough.
Another half inch to an inch appears possible.  After a brief period
of high pressure on Saturday night into Sunday, a cold front will
move across the area later Sunday into Sunday night, before stalling
southeast of the region early next week.  As waves of low pressure
travel northeast along the front, periods of precip are expected to
occur later Sunday into Tuesday.  Too early to get into the details
just yet, but appears several inches of snow will be possible over
northern WI during this time.  Snow potential over central to east-
central will be partly determined by whether if temps warm enough
for a wintry mix to occur.  Arctic high pressure then returns for
next Wednesday.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1136 AM CST Wed Feb 14 2018

Clear skies and good visibility expected through at
least the early evening hours. Some low clouds may form by late
evening mainly north of a ISW to IMT line. Low level wind shear
possible after midnight with southwest winds around 10 knots at
the surface and southwest winds around 35 knots at 1000 ft. Whatever
low clouds do form later tonight should dissipate from south to
north Thursday morning.
&&

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

$$

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


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