Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 251923

Area Forecast Discussion
National Weather Service Green Bay WI
223 PM CDT THU AUG 25 2016

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Friday
Issued at 223 PM CDT Thu Aug 25 2016

The main frontal boundary continues to sag over the mid
Mississippi valley and Ohio valley region today with SPC slight
risk regions noted. Mid to high level clouds associated with a
surface wave which produced convection over southeast Wisconsin
overnight continues to move eastward.

After a period of sunshine this afternoon...clouds will be on the
increase. Mid to mostly high level clouds from convection near a
boundary over southeast Nebraska and southern Iowa was spreading
into the state this afternoon. Meanwhile a trough of low pressure
over northern Minnesota associated widespread clouds and isolated
to scattered showers was slowly drifting toward the northern Great
Lakes region this afternoon. Anticipate these clouds will
continue to work across parts of northern Wisconsin tonight into
Friday morning. Some challenge with how much of these clouds will
work into the northern Wisconsin since upper heights increase
tonight, but will continue to focus on lower clouds with the 80
percent relative humidity region of the boundary level...or mainly
north of Merrill.

Cloud trends and affect on max/min temperatures may continue to
provide challenges into Friday even though high pressure drifting
over area. The lower level clouds may be persistent across the
north, along with a few sprinkles or light rain showers,
especially during the morning hours. Even though the primary
front is well south of the area, RRQ region of the upper jet from
the central plains into southern wisconsin may aid with sending
more mid to high level clouds into at least the south half of the
state Friday.

.LONG TERM...Friday Night Through Thursday
Issued at 223 PM CDT Thu Aug 25 2016

The primary issue after Friday evening centers on the next
frontal system for the weekend. Potential of another soaking
rainfall as Pwats climb to 1.50 inches. Model consensus the last
few days was a faster arrival starting Saturday morning and then
trending into late friday night. This mornings NAM and GFS run did
not shift much with respect to timing but coverage of rain has
diverted between these runs...especially the warm air advection
portion of the system. GFS runs the warm air advection over the
southeast half of the state Saturday morning with a separate area
of convection over the northern plains with the short wave trough
and cold front. The nam lifts a more intense area of warm air
advection precipitation more into eastern Minnesota and western
Wisconsin, along with a deeper surface low pressure system over
southeast Minnesota. The nam tracks the surface low northeastward
over the state saturday while the GFS surface low position is
further west near the upper trough. The ECMWF is similar to the
GFS in some features but is a bit faster with the arrival of the
pcpn Friday night. The GFS best instability remains well south
through Saturday and provides a threat of a complex south of the
area intercepting the deeper moisture at the onset. The NAM has
not issue with lifting unstable air into the state with the deeper

The brunt of the convection should come to an end from west to
east Saturday night as the short wave trough lifts northeast and
the surface cold front slides through, departing eastern
Wisconsin late Saturday night.

Pattern for later Sunday into the new work week shifts from a
zonal flow to a developing upper ridge over the area through at
least mid week. Not surprisingly, the medium range progs are all
over place with precipitation chances at the onset due to faster
westerly flow aloft. Return flow already setting up over the
Northern Plains Sunday night which could spill into the state
late Sunday night into Monday. Progs divert further with the
surface front position on Tuesday and then return flow developing
again by mid week as upper heights build.  Confidence with timing
of convection for the new work week is low.

.AVIATION...for 18Z TAF Issuance
Issued at 1051 AM CDT Thu Aug 25 2016

VFR conditions will prevail today and most areas tonight. For
tonight, a trough of low pressure passing over the northern Great
Lakes region may allow sct-bkn MVFR clouds to sag into parts of
north central Wisconsin. Later tonight, patchy fog will also be
possible across north central Wisconsin.



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