Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 131620

Area Forecast Discussion
National Weather Service Green Bay WI
1020 AM CST Fri Jan 13 2017

Updated aviation portion for 18Z TAF issuance

Issued at 330 AM CST Fri Jan 13 2017

Cold today, then warming temperatures. A round of mixed
precipitation is likely early next week.

During the next week, two strong upper height anomalies will
evolve near North America. A negative anomaly will develop near
Alaska and then expand southward down the west coast during the
week, while a strong positive anomaly settles in over eastern
Canada. The fairly long wavelength between the two features favors
splitting of the upper flow.

The upper changes will cut off the direct flow of arctic air into
the area, so cold temperatures at the start of the forecast period
will give way to significantly above normal readings for the
latter half of the period. Receiving significant precipitation
will depend on getting southern stream systems to affect the area.
At this point there appears to be one such system, which will
arrive early next week. Normal precipitation for a week at this
time of year is about three-tenths of an inch, and the early week
system seems likely to produce at least that much precipitation.

.SHORT TERM...Today...Tonight...and Saturday
Issued at 330 AM CST Fri Jan 13 2017

Much quieter than the past few days. The final surge of arctic
air (at least for a while) will be moving through the area and
begin shifting off to the east. Some high and middle clouds will
move across the area today. Some weak forcing will move across the
area tonight as low-level isentropic lift and a mid-level
shortwave shift through the region. Low levels will start out
dry, and much of the lift will be needed to achieve saturation.
Models have backed away from the light QPF they had been showing
for a few days. While change seems reasonable, opted to keep
flurries in the forecast.

The ongoing Wind Chill Advisory is marginal as winds are dying off
with the approach of the low-level anticyclone. But since those
sites that still have wind have WCI`s in the -20 to -25 range,
will leave it intact.

.LONG TERM...Saturday Night Through Thursday
Issued at 330 AM CST Fri Jan 13 2017

Main concern for this period will be the system moving across the
region Monday into Tuesday. A wintry mix is expected with some
potential for ice accumulations across the entire area. It appears
the greatest icing will occur north and west of the Fox Valley at
this time.

Some differences noted in when the precipitation arrives late
Sunday night into Monday morning. Continued with a small chance
of light snow towards daybreak across our southern counties.
The precipitation should start out primarily as snow, but could
be mixed with sleet or freezing rain. As the morning progresses,
warmer air flowing northward into the region will change any snow
over to freezing rain or sleet across the southern half of the
forecast area. Air temperatures across much of the area will be
below freezing for much of the day, except across the Fox Valley
and lakeshore where easterly winds off the warmer waters of Lake
Michigan will allow temperatures to rise a few degrees above
freezing. Although temperatures may be a few degrees above
freezing, the recent cold spell has caused pavement temperatures
to plummet well below freezing and would need more time to
recover. Do think this region will see some light icing, then
change over to rain Monday night into Tuesday morning.

It gets more interesting north and west of the Fox Valley where
this area is usually slower to respond to rising temperatures,
especially at night. To complicate matters, 850mb temperatures
continue to rise and will be several degrees above freezing. It
probably won`t be until late Tuesday morning until most of the
area will be warm enough for rain and air/road temperatures climb
above freezing. Ice amounts around a tenth of an inch are
possible. If pavement temperatures do not respond, ice accumulations
will be somewhat greater on area roads, bridges and sidewalks. The
main system expected to move across the region on Tuesday,
bringing an end to the steadier precipitation Tuesday afternoon or
evening. Some precipitation may linger across the far north
Tuesday night.

The remainder of the period will be tranquil with above normal
temperatures expected into next weekend.

.AVIATION...for 18Z TAF Issuance
Issued at 1019 AM CST Fri Jan 13 2017

With high pressure drifting over the area today into
Saturday, VFR conditions to dominate. Mainly mid to high level
clouds passing over the region during the period.



SHORT TERM.....Skowronski
LONG TERM......Eckberg
AVIATION.......TDH is the U.S. government's official web portal to all federal, state and local government web resources and services.