Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 231955

Area Forecast Discussion
National Weather Service Green Bay WI
255 PM CDT SUN OCT 23 2016

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Monday
Issued at 254 PM CDT Sun Oct 23 2016

Main forecast focus to be primarily centered on tonight with
precipitation across the north ending and the question of cloud
trends overnight with their affects on min temperatures.

The 19z MSAS surface analysis indicated an area of low pressure
over east-central Wisconsin. A warm front extended southeast from
the low into southern Lake MI with a cold front stretched
northwest from the low through central MN. The bulk of the light
rain showers were actually moving across northern sections of the
Great Lakes in association with the passage of a mid-level
shortwave trough. Farther to the west...and area of high pressure
was located over the northern and central Plains.

Any lingering light showers or sprinkles over far northeast
Wisconsin is forecast to end by early evening as the surface low/
cold front/mid-level shortwave trough all quickly shift toward the
eastern Great Lakes. The rest of the night will be dry as the
broad area of Canadian high pressure shifts east into the Upper
Midwest. Skies over central and east-central Wisconsin should
gradually become at least partly cloudy, while clouds over the
north may hold tougher due to cool northwest winds moving over
Lake Superior. Min temperatures will be a bit tricky depending on
the cloud trends later tonight. For now, have temperatures dipping
into the lower 30s north, lower to middle 30s central/far
northeast and 35-40 degree range east-central Wisconsin.

Anticipate more widespread sunshine for Monday as the high
pressure moves into the western Great Lakes region and winds back
a bit to the west-northwest (less lake effect clouds). Despite the
sun being out, temperatures will only be around normal for late
October as upper ridging over the central CONUS brings a northwest
flow aloft into Wisconsin. Look for readings to reach the upper
40s to around 50 degrees north, lower to middle 50s south.

.LONG TERM...Monday Night Through Sunday
Issued at 254 PM CDT Sun Oct 23 2016

The main forecast concerns will be precipitation timing and type,
and how much rainfall will occur, with the strong low pressure
system moving through the western Great Lakes Tuesday night into

Dry and seasonable weather is anticipated Monday night and Tuesday,
as Canadian high pressure resides over the region. Clouds will be
on the increase Tuesday, as low pressure approaches from the plains.

Models have come into better agreement with the timing of
precipitation onset with the midweek system. The general concensus
is that rain will overspread about the southwest half to two-
thirds of GRB CWA Tuesday night, and fill in over far northeast WI
early Wednesday. If this slower progression is correct, the
precipitation should be nearly all rain through Wednesday. Feel
confident that pops can be raised to categorical over the entire
forecast area on Wednesday, with near 100 percent over our
southern counties. A gradual decrease in pops is expected from
west to east Wednesday night into Thursday morning, as the surface
and upper lows shift east. During the latter stages of this
system, enough cold air may wrap into northern WI to allow a mix
of rain and snow to occur, with little or no accumulation. Strong
dynamic forcing will combine with a moist air mass (PWATs 0.75 to
1.00 inch) to produce total rainfall of 1 to 2 inches over central
and east central WI.

Forecast confidence derails later in the week, with the GFS
showing a cold frontal passage on Friday, and Canadian high
pressure over the weekend, while the ECMWF supports a low pressure
system passing to our south and producing precipitation over the
forecast area Saturday into Sunday. GFS ensembles members also
show wild variations. Given the very low confidence in the weekend
forecast, will stick with the preferred model blend for now.

.AVIATION...for 18Z TAF Issuance
Issued at 1224 PM CDT Sun Oct 23 2016

A modest area of low pressure is expected to move from central
Wisconsin east-southeast into Lower MI by this evening. A cold
front will also sweep through the rest of Wisconsin this afternoon
and turn the winds to the north and increase speeds into the 10 to
20 knot range with a few higher gusts. The bulk of light rain
showers across northern Wisconsin is more associated with the
passage of a mid-level shortwave trough over the northern Great
Lakes. This area of precipitation is forecast to come to an by
early evening. An area of high pressure will move into the Upper
Midwest tonight and into the western Great Lakes on Monday. An
influx of drier air will gradually dissipate the clouds later
tonight with a good amount of sunshine on Monday. Cigs could dip
into the MVFR range late this afternoon into the evening hours.
Otherwise, VFR conditions should prevail from later tonight
through Monday.



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