Area Forecast Discussion
Issued by NWS Green Bay, WI

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643
FXUS63 KGRB 291927
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
227 PM CDT FRI JUL 29 2016

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Saturday
Issued at 225 PM CDT Fri Jul 29 2016

The latest RAP analysis and satellite/radar imagery show northern
Wisconsin positioned between high pressure over Lake Superior and
low pressure spinning from eastern Iowa to central Indiana.  Showers
and storms continue to redevelop over southern WI and northern IL
early this afternoon.  The northern extent of the shower activity
has pushed into the Oshkosh and Wautoma areas, and some of these
showers may spread west into Wood and Portage counties later this
afternoon.  Widespread cu has developed with the heat of the day
over north-central and northeast WI west of the Bay, while some
clearing is starting to move into far eastern WI.  Forecast concerns
revolve around minor precip chances and cloud trends.

Tonight...The weak shortwave will slowly move across southern WI and
northern IL tonight. As this occurs, weak high pressure building
south into the Lake Superior region will send drier air into the
northeast part of the state through the evening hours.  As a result,
think that the widespread diurnal cu will mix out across northern WI
this evening, while partial clearing moves into central and east-
central WI areas.  These areas may not clear out entirely, but
guidance suggests this is possible late tonight.  Any threat of
showers should also diminish this evening as well.  With clear skies
and light winds across the north, patchy fog will be possible after
midnight.  Lows ranging from near 50 in the far north, to the low
60s near Lake Michigan.

Saturday...The broad, low amplitude shortwave will remain present in
upper levels, but much drier air will be present below 700mb.
Scattered to broken clouds will likely persist into the morning
hours over the southern Fox Valley and I-39 corridor before evolving
into a cu field by midday.  Should see some cu pop elsewhere as
well, but coverage should be considerably less widespread compared
to todays.  With more sunshine expected, temps will be warmer and
rise into the mid and upper 70s.

.LONG TERM...Saturday Night Through Friday
Issued at 225 PM CDT Fri Jul 29 2016

Canadian high pressure and associated drier air will be ridged
across the northern Great Lakes for the late weekend and early
next week. Several models generate spotty and weak afternoon
convection on Sunday as a weak s/w trof encounters daytime
instability, but there was poor agreement on the location, and
coverage is expected to be isolated, so kept the dry forecast
intact. A building upper ridge should preclude precipitation
development on Monday. With mostly clear skies and light boundary
layer winds expected, have opted to add patchy fog late Saturday
night and Sunday night.

An 850 mb warm front is expected to make a push for the forecast
area late Monday night into Tuesday, so a chance of thunderstorms
should return during this time period. There may be a lull in
organized convection Tuesday night into Wednesday as upper level
ridging occurs. However, a cold front will approach the region
late Wednesday night, and move through the forecast area Thursday
and Thursday night, bringing another chance of thunderstorms. The
GFS brings very warm mid-level temperatures into the region ahead
of the front, perhaps capping off convection for a while, but the
ECMWF is less aggressive with the cap. Both models show moderate
to strong instability and ample deep-layer shear for severe tstms
with the cold frontal passage, so we will need to keep an eye on
this with subsequent forecasts. Very warm and muggy conditions
will also return during the midweek period, along with the
potential for locally heavy rainfall, as precipitable water
values increase to 1.5 to 2 inches.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1207 PM CDT Fri Jul 29 2016

A weak upper level trough will slowly drift over the state today
into this evening. Ceilings will likely remain mvfr over central and
east-central WI until late this afternoon or mid-evening, with
isolated showers possible generally south of a Wausau to Manitowoc
line.  Coverage is too limited to include in the tafs, though higher
probability of a shower exists at Oshkosh and Manitowoc. Model
guidance indicates that ceilings will improve this evening as drier
air finally moves in from the northeast.  Flying weather looks good
for Saturday.
&&

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

$$

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



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