Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 201029
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
529 AM CDT Wed Sep 20 2017

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Thursday
Issued at 349 AM CDT Wed Sep 20 2017

Convective trends today into this evening with a cold front
passage will be the primary issue. Early this morning, NWS
Minnesota offices were issuing severe thunderstorms warnings for
Wisconsin counties adjacent to Minnesota. Convection associated
with moisture convergence in the LLJ region ahead of the cold
front. MU capes approaching 2500 j/kg near the WI/MN border.
Expect this convection to continue to work into NW Wisconsin
early this morning then diminish as the band works ahead of the
best instability and deep layer shear over Minnesota. Will need to
watch trends on the southern portion of the line east of MSP to
see if this will reach North Central Wisconsin toward daybreak.

Meanwhile surface analysis early this morning is showing the
surface cold front is starting to lag back of this initial
convection. So while this first band diminishes, short range
progs redevelop convection midday over central and north central
Wisconsin as the cold front works over the state and instability
axis shifts into the Wisconsin. Still some potential of strong to
severe storms due to time of the day and available instability,
but the front is working into a ridge and upper heights do
increase late this afternoon into tonight and the upper jet
continues to lift northwest of the area. A SPC marginal risk of
storms continues over most of the area today and evening.

High pressure builds into the area late tonight into Thursday
morning in the wake of the cold front passage. Currently have a
dry forecast for Thursday, but it is possible a chance for
showers and storms will be needed due to 850 winds turn
southwesterly quickly in response to the building heights and a
frontal boundary may initially be close to east central and
central Wisconsin starting Thursday morning.

.LONG TERM...Thursday Night Through Tuesday
Issued at 349 AM CDT Wed Sep 20 2017

The main story for the beginning of the period will be unseasonably
warm temperatures Thursday through the weekend. The warmth should
peak Friday through Sunday, with average temperatures running 15
to 25 degrees above normal each day. High temperatures will be
close to the record high for each day. Temperatures by early next
week will return closer to normal.

Weak high pressure will slide east of the are Thursday night.
Return flow/850mb warm advection noted which could trigger an
isolated shower or thunderstorm across northern Wisconsin.
Continued with small chances of rain for the above mentioned
reasoning. Very warm and increasing humidity expected on Friday
with highs well into the 80s. A few 90 degree readings are
possible across central into northeast Wisconsin. So far this
year, Green Bay, Rhinelander and Wausau have not reported a 90
temperature so far this year. The warmth then continues through
Sunday. Shower and thunderstorm activity north and west of the
state may spill over into far north-central Wisconsin at times
Saturday afternoon into Sunday evening.

Rain chances will be on the increase Monday into Tuesday, although
Tuesday will probably be the better day for rain. The two tropical
systems (tropical storm Jose and hurricane Maria) moving northward
off the coast of the United States will slow the overall weather
pattern down across North America.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 529 AM CDT Wed Sep 20 2017

Moisture working northward on south winds will produce
patchy IFR clouds and fog over eastern Wisconsin early this
morning. Mainly mvfr cigs are expected later today into this
evening as a cold front with scattered showers and storms tracks
over the area. A few storms may contain large hail and gusty
winds. Depending on how quickly the front departs tonight
followed with a decreasing cloud trend and diminishing wind, low
stratus and fog may begin to spread into north central and
central Wisconsin late tonight.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement from 1 PM CDT this afternoon through
this evening for WIZ022-040-050.
&&

$$

SHORT TERM.....TDH
LONG TERM......Eckberg
AVIATION.......TDH



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