Area Forecast Discussion
Issued by NWS Green Bay, WI

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KGRB 091800
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1200 PM CST Mon Dec 9 2019

Updated aviation portion for 18Z TAF issuance
and new information added to update section

.UPDATE...
Issued at 1153 AM CST Mon Dec 9 2019

Decided to issue a winter weather advisory for the Fox Valley
and lakeshore region from 3 pm to 8 pm this evening. A band of
heavy snow is expected to move across the area between 3 pm to
6 pm. Visibilities in the heavier snow band will drop to less
than a half mile for the afternoon commute. Lingered the advisory
into the early evening hours as gusty northwest winds are expected
behind the cold front. Gusts to 30 mph will create areas of
blowing and drifting snow.

&&

.SHORT TERM...Today...Tonight...and Tuesday
Issued at 410 AM CST Mon Dec 9 2019

The main concerns for this portion of the forecast will be the
potential for drizzle/freezing drizzle this morning along with
widespread snow this afternoon. No major changes in the snowfall
totals or headlines for today. Some slippery stretches are possible
through the morning commute over the Fox Valley and along the Door
Peninsula, but any slippery conditions should improved through mid
morning.

Today: A surface low is expected to shift from northern MO/southern
IA at 12Z to Lake Huron by 00Z Tuesday. As this happens, moisture is
expected to deepen to the northwest of the surface low and near the
850mb low. Forcing will also increase across all of the area as a
coupled jet structure is expected to slide across the area
throughout the day. Much of northeast WI will be on the southern
fringes of the right-entrance region of a northern stream jet and
the northern fringes of the left-exit region of the southern stream
jet. Moisture is expected to deepen across the area throughout the
day and cold air advection aloft will combine to increase the
probability of ice crystal introduction into the cloud layer. This,
in simple terms, will allow the drizzle/freezing drizzle to
transition over to mainly snow throughout the day. The moisture in
the DGZ is expected to become fairly deep across the central into
north-central WI by this afternoon, allowing snow ratios to increase
and snow intensity to increase. Farther east, across east-central
and far northeast WI, it will likely take longer for the cold air
and deeper moisture to transition the precipitation to all snow.
Accumulations are expected to range from 3 to 5 inches across
central and north-central locations to around 1 to 3 inches across
the Fox Valley into far northeast WI, with the lowest totals
expected along the lakeshore. Some minor flooding may occur along
the Bay as northeast winds increase through the morning hours, but
should not be as bad as the last couple events. High temperatures
will range from the 20s northwest to mid 30s southeast, with
steadily dropping temperatures in the afternoon.

Tonight into Tuesday: As the low pressure system shifts from Lake
Huron into Quebec, expect some wrap-around moisture to linger across
eastern portions of the area into the early evening hours. Moisture
will be deep enough across the area at that point to keep the
precipitation in the form of light snow. Not expecting much more
than an additional half inch or so across the Fox Valley into the
Door Peninsula. Otherwise, with northwest to west-northwest flow,
some light lake effect snow may push into northern Vilas County
tonight into early Tuesday morning as 850mb temps drop to around -
20C to -24C. By late Tuesday morning into the afternoon hours, winds
will shift far enough west to push the lake effect potential into
Upper Michigan. Only minor accumulations are expected across
northern Vilas County. Temperatures will be below normal for this
time period with highs in the single digits to low teens above zero
with overnight lows dropping into the single digits above and below
zero.

.LONG TERM...Tuesday Night Through Sunday
Issued at 410 AM CST Mon Dec 9 2019

The largest impacts over the next week mainly revolve around the
bitter cold Tuesday night into Thursday morning, followed by
intermittent light snow chances thereafter.

Tuesday night through Wednesday night...Arctic high pressure will be
sliding southwest of the region on Tuesday night.  The coldest air
of the season will be arriving by early Wednesday morning, with west
winds of 5 to 10 mph creating wind chills of 15 to 25 below zero.
Wind chills this low will likely lead to wind chill advisories for
central and north-central WI.  Shortwave energy will be passing
across the region on Wednesday morning.  Snow chances look to remain
along and north of the U.P. border, as well as over southern
WI/northern IL with this wave.  After a bitter cold day with highs
only in the single digits above zero, arctic high pressure will
become centered directly over the region on Wednesday night.
Normally this setup would promote very cold low temps, but models
continue to insist on mid and high clouds pushing in from the west.
The may be a brief opportunity for temps to tank in the evening, and
will trend towards colder guidance.

Rest of the forecast...The latest model runs are more aggressive
generating light snow on Thursday in a weak warm advection regime
with help from a shortwave impulse.  Thermal profiles are excellent
for dendritic snow growth over far northern WI, which should support
slightly higher snow totals over this area than further south and
east.  But in the end, think amounts will be relatively light, maybe
up to inch, possibly two on the high end.  Temperatures will be
moderating Thursday into Friday, with readings warming into the 30s
by Friday afternoon.  Shortwave energy will be moving across the
area at times from Friday through the weekend.  Early indications
suggest that Friday night into Saturday will offer the next best
chance of widespread precip.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1153 AM CST Mon Dec 9 2019

Drizzle and freezing drizzle will switch over to snow this
afternoon from west to east. A band of moderate to heavy snow
will sweep across the area along and just behind the cold front
with IFR and lower conditions. The precipitation should gradually
end from west to east across much of the area late this afternoon
and evening, except across the far north where snow showers will
linger into Tuesday morning. Gusty northwest winds to near 30
knots are possible across much of the area this afternoon into
early this evening, then gradually diminish overnight. CIGS
expected to rise into the MVFR/VFR category tonight. Winds back
to the west on Tuesday.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 3 PM this afternoon to 8 PM CST
this evening for WIZ022-038>040-048>050.

Winter Weather Advisory until 6 PM CST this evening for WIZ005-
010>013-018>021-030-031-035>037-045-073-074.
&&

$$

UPDATE.........Eckberg
SHORT TERM.....Cooley
LONG TERM......MPC
AVIATION.......Eckberg


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.