Area Forecast Discussion
Issued by NWS Green Bay, WI

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443
FXUS63 KGRB 151735
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1135 AM CST Thu Feb 15 2018

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Friday
Issued at 408 AM CST Thu Feb 15 2018

Low clouds did not form as expected early this morning, so much
of the forecast area remained clear. A short-wave trof moved
through northern WI overnight, bringing some cloud cover to our
far northwest counties, but precipitation stayed to our west and
north. MSAS analysis showed a cold front approaching Duluth, but
southwest winds ahead of it were holding temperatures in the upper
20s and 30s across northeast WI.

Given the current mild temperatures, a lack of thick cloud cover
and a gradual frontal passage, it seemed reasonable to raise
temperatures 3 to 5 degrees above the previous forecast. A few
spots may warm into the middle 40s in central and east central
WI. Most of the day is expected to be dry, though RH timesections
show moisture increasing over north central and central WI later
in the afternoon. Lake-effect potential will also increase in the
Lake Superior snow belt later in the day as cold northwest flow
develops. The best chance of precipitation will be over Vilas
county, but kept pops in the chance category.

Lake effect snow showers will continue over Vilas county through
at least midnight. Additional snow showers are possible across
central and east central WI as a short-wave trof moves through.
The precipitation should end overnight, with clearing occurring
from west to east late tonight into early Friday. Much colder air
will arrive, with lows ranging from the single digits below zero
northwest to the middle teens southeast.

High pressure will bring a sunny and cold day on Friday, with
highs in the teens and lower 20s.

.LONG TERM...Friday Night Through Wednesday
Issued at 408 AM CST Thu Feb 15 2018

The main forecast concern in this part of the forecast includes
precip chances late in the weekend into early next week.  The medium
range models continue to indicate that a pattern change will occur
during the above time period, when a deep trough digs over the
western U.S., turning the upper flow to southwest over the western
Great Lakes.  The models have significant detail differences by
Sunday and will use a blend of the gfs/ecmwf.

Friday night through Saturday night...Arctic high pressure will
quickly shift to the eastern Great Lakes on Friday night.  Mid and
high clouds will move into the region ahead of the next shortwave
trough.  These clouds combined with a southwest wind should result
in warmer temperatures.  The shortwave trough will pass across the
region on Saturday.  Best forcing will pass south of the region, but
will still see a small chance of snow for much of the area.  A
dusting to a half inch of accumulations appear possible.  A brief
period of clearing then will occur on Saturday night, with the next
round of clouds already arriving late.

Rest of the forecast...The upper flow will begin buckling on Sunday,
shifting to the southwest, and result in increasing warm advection
across the area.  Models continue to point towards a band of precip
extending eastward across northern WI into the Upper Peninsula on
Sunday, but differ on placement.  A further south solution could
result in several inches of snow over northern WI on Sunday into
Sunday night.  Low pressure will then travel across the southern
Great Lakes on Monday and Monday night.  Periods of precipitation
can be expected during this time, though the precip type will be
dependent upon the temperature profile.  Models have indicated for
the past couple days that enough warm air will surge into east-
central to northeast WI for a wintry mix, while northern WI will
mainly consist of snow.  Probably too early to get wrapped up in the
details this far out, but focus right now is appears to be on
northern WI for the possibility of heavy snow.  The pattern will
also be conducive for a stripe of freezing rain as well. Depending
upon where the Arctic front stalls, could see precip chances
continue into Tuesday over northeast WI, but confidence is very low
by this time. High pressure then returns for the middle of next week.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1135 AM CST Thu Feb 15 2018

A cold front will bring VFR/MVFR clouds as it moves
across the area this afternoon. Some snow flurries are expected
behind the front tonight, with BKN to OVC ceilings between 2500
and 3500 feet. The clouds should exit the area by 12z Friday, with
good flying weather Friday through Friday night.
&&

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

$$

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



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