Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 250419
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1019 PM CST Sat Feb 24 2018

Updated aviation portion for 06Z TAF issuance

.UPDATE...
Issued at 703 PM CST Sat Feb 24 2018

Updated the wind advisory to include counties adjacent to Lake
Winnebago including Winnebago and Calumet counties. Some potential
gusty wind locations include north/south roadway bridges of
highway 41, higher terrain of Calumet county by Lake Winnebago.
Brown county appears to have less of a threat to reach criteria
but still close.

Air surface temps dropped to around the freezing mark early this
evening prior to the precipitation, but locations not in the
advisory should warm up enough. No other headline changes at this
time.
&&

.SHORT TERM...Tonight and Sunday
Issued at 228 PM CST Sat Feb 24 2018

The latest RAP analysis and satellite/radar imagery show an area
of strengthening low pressure moving northeast over southwest
Missouri early this afternoon. This low is developing ahead of a
sharp shortwave trough extending southeast across the north-
central Plains. Strong convection is developing ahead of the low
over southern Missouri and Arkansas. Meanwhile, isentropic ascent
is increasing over the southern Great Lakes, with snow occurring
over southern Minnesota and northern Iowa. Light returns over
southern WI do not appear to be reaching the ground just yet. But
as the low moves closer, light precip is anticipated to be
approaching central WI by later this afternoon. As the low moves
across the region tonight, snowfall amounts and gusty winds are
the main forecast concerns.

Tonight...A potent, negatively tilted shortwave trough will push a
strengthening area of low pressure northeast across the area.
Ahead of the low, increasing moisture transport in the mid-levels
will help spread precip from southwest to northeast across the
region from late afternoon through mid-evening. However, the
heaviest precip should occur from mid-evening through the mid-
overnight hours, just ahead of the potent vort max and surface
low. Warm air will surge northward into parts of central and most
of northeast WI during the evening, which will keep precip types
south of a Wisconsin Rapids to Marinette line as mostly rain with
some snow/sleet mixed in. Areas to the north will see mostly
snow, and snowfall rates could reach an inch per hour at times
during the peak snowfall period. Forecast amounts didnt change
much from the previous forecast, though did increase an inch or
two from Langlade and Menominee to Marinette counties. As a
result, added southern Marinette into the advisory since northern
parts could reach up to 5 inches. In general though, a widespread
3 to 6 inches will be possible, with slightly higher amounts over
Vilas and Oneida counties.

As snowfall diminishes late tonight, strong pressure rises will
arrive behind the deepening low. Combined with cold advection and
a tightening pressure gradient, will see southwest winds become
strong and gusty. Some gusts over the Fox Valley and Lakeshore
could approach 40-45 mph range by 6 am.

Sunday...Some light snow or freezing drizzle may linger for the
first few hours of the morning over far north-central WI. Little
to no additional accumulations are expected. Otherwise, the big
story will be the strong gusty winds. Wind gusts should peak
during the morning, with gusts between 30 to 40 mph possible for
most of the area, and up to 45 mph near the Lakeshore. Will hoist
a wind advisory from 10-21z for the Lakeshore, though it may be
cancelled a little early once the max pressure rises move through
around midday. With increasing sunshine though the day, highs will
warm into the upper 20s over north-central WI to the mid 30s over
eastern parts of the state.

.LONG TERM...Sunday Night Through Saturday
Issued at 228 PM CST Sat Feb 24 2018

The weather pattern will start off with zonal flow and a weak ridge
of surface high pressure over the region. Dry and milder conditions
are anticipated through Monday night, with only a small chance of
showers as a weak cold front arrives on Tuesday.

The front is expected to stall out Tuesday night and Wednesday,
with weak overrunning leading to light rain/snow development over
mainly the southeast half of the forecast area. Mild temperatures
will continue, with highs in the upper 30s to middle 40s.

A sharp upper trof crossing the central Rockies will induce
cyclogenesis near the Oklahoma Panhandle on Wednesday. This low
(and the associated deepening upper trof/low) will track northeast
along the stalled frontal boundary, and approach the western Great
Lakes late Wednesday night into Thursday. The GFS is farther
north with the sfc/upper lows, and brings the potential for heavy
snow into GRB CWA, while the ECMWF is farther south and keeps the
main impacts to our south. Surface and 850 mb temperatures
support mixed precipitation, especially early in the event, with
CAA and possible dynamic cooling resulting in a changeover to all
snow during the late afternoon or evening. Strong northeast to
north winds are also anticipated, along with the potential for
Gale Warnings Thursday and Thursday night. Will continue to
mention this system in the HWO, but hold off on any specific
details at this time.

Quiet weather is expected to return as high pressure arrives
Friday into Saturday.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1018 PM CST Sat Feb 24 2018

IFR cigs and vsbys due to mixed precipitation will
continue to around 10z this morning then being to improve to MVFR
by daybreak as a cold front sweeps through. Conditions will
continue to improve to VFR Sunday morning, however strong west
surface winds of 20 to 30 knots will increase Sunday morning.
Higher gusts to 30 to 40 knots are expected over the Fox Cities
and toward Lake Michigan. Winds are expected to begin tapering off
later Sunday afternoon.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 3 AM to 3 PM CST Sunday for WIZ022-039-040-
048>050.

Winter Weather Advisory until 6 AM CST Sunday for WIZ011>013-
018>021-030-031-035>037-073.

Winter Storm Warning until 6 AM CST Sunday for WIZ005-010.
&&

$$

UPDATE.........TDH
SHORT TERM.....MPC
LONG TERM......Kieckbusch
AVIATION.......TDH


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