Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 140340
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1040 PM CDT Fri Oct 13 2017

Updated aviation portion for 06Z TAF issuance
and new information added to update section

.UPDATE...
Issued at 1032 PM CDT Fri Oct 13 2017

Lingering low-level moisture, light winds and partial clearing
have resulted in areas of fog, especially in central WI. Have
added fog to the forecast and issued a Special Weather Statement
to cover locally dense fog for the overnight period. Expect fog
to mix out later tonight as winds slowly pick up.

&&

.SYNOPSIS...
Issued at 245 PM CDT Fri Oct 13 2017

Wet, windy, and turning briefly colder this weekend, then mild
and quiet weather to return next week.

The amplified upper flow across North America will flatten the
next several days as the bulk of the energy within a western
longwave trough ejects eastward. The resulting energetic but
zonal regime of early next week will gradually amplify later in
the week, with a trough once again forming near the West Coast
and downstream ridging over central and eastern NOAM.

Daily temperatures will vary between near and modestly above
normal throughout the period. Precipitation amounts are likely to
end up AOA normal, with the primary precipitation producer being
the cyclone that crosses the region this weekend. The prospect for
significant precipitation during the remainder of the period
appears low.
&&

.SHORT TERM...Tonight and Saturday
Issued at 245 PM CDT Fri Oct 13 2017

The main short-term forecast issue is the timing of rain chances
with the initial wave crossing the area this evening, and the
arrival of the main system tomorrow. Overall, the models were in
pretty good agreement, though the NAM and hi-res WRFs were
considerably slower with the northward push of rain ahead of the
primary cyclone tomorrow. Trended the forecast toward the
majority, but held PoPs across the north back until late in the
day in case the NAM/WRFs are onto something.

Stayed with a limited diurnal temperature range for most areas.
But given the likelihood of a period with mostly clear skies and
light winds across the north tonight, lowered mins there toward
the min of the distribution of guidance low temperatures.

.LONG TERM...Saturday Night Through Friday
Issued at 245 PM CDT Fri Oct 13 2017

Low pressure will move from southeast Colorado to southern Lake
Michigan Saturday through Saturday night, as an upper trough moves
across the central plains to the Great lakes. The system doesn`t
seem quite as dynamic as it did yesterday, but is still strong
enough to bring significant rain and a few thunderstorms. Rainfall
amounts of an inch or so are possible.

The surface low intensifies quickly as it moves from southern Lake
Michigan Saturday evening to western Quebec, producing a strong
pressure gradient that will produce gusty northwest winds Sunday.
The rain should end early Sunday as the surface system exits the
area. Blustery and cool weather is expected Sunday afternoon.

The 500mb flow is forecast to become nearly zonal Tuesday through
Friday, which should result in dry and mild weather for
Wisconsin.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1032 PM CDT Fri Oct 13 2017

Rain has ended and low ceilings have eroded over most of the
forecast area. However, lingering low-level moisture has combined
with light winds and partial clearing to produce areas of fog. So
far, the lowest visibilities have been in parts of central and
north central WI. Current thinking is that the fog will persist
until around 08z-09z, followed by improving conditions as surface
and boundary layer winds increase.

The improving conditions will be temporary, as rain and lowering
ceilings will return to central and east central WI in the late
morning and early afternoon on Saturday, then spread into northern
WI later in the day. Flight conditions will deteriorate to IFR at
GRB/ATW/MTW during the mid to late afternoon as the rain
intensifies, and most locations should drop to LIFR Saturday
evening.
&&

.MARINE...
Issued at 245 PM CDT Fri Oct 13 2017

An intensifying area of low pressure will move through the
region Saturday night into Sunday morning. Initially, east winds
are expected to increase Saturday afternoon with waves approaching
small craft advisory criteria (4 ft) on Lake MI. The winds may
briefly diminish Saturday evening as low pressure moves across
Wisconsin. As the surface low departs later Saturday night, winds
are forecast to rapidly shift to the northwest and become gusty
into Sunday. A period of gale force gusts are possible from late
Saturday night through Sunday afternoon.
&&

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

$$

UPDATE.........Kieckbusch
SYNOPSIS.......Skowronski
SHORT TERM.....Skowronski
LONG TERM......RDM
AVIATION.......Kieckbusch
MARINE.........RDM



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