Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 171039

Area Forecast Discussion
National Weather Service Green Bay WI
539 AM CDT Thu Aug 17 2017

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Friday
Issued at 313 AM CDT Thu Aug 17 2017

Convection trends today into this evening the focus of this
forecast period.

At 230 am, the leading band of showers with the 850 warm front
was lifting over northern Wisconsin early this morning. Scattered
convection was noted over west central Wisconsin as the upper low
continues drifts into the state from Minnesota. This second area
of convection was also associated with the dry slot working into
northwest Wisconsin and the LFQ region of a weak upper jet.
Lightning data shows isolated storms near this dry slot as per
water vapor loop, but no other lightning data. The surface low
pressure center was over MSP with a warm front extending into
southwest wisconsin and a cold front just to the west. With pwats
in the 1.50 to 2.00 range early this morning, there was some
potential for heavy rainfall, but the 35 kts LLJ was allowing a
quick storm movement, before the higher pwats shift to the east
toward daybreak. Expect isolated convection to become more
scattered today as the surface low and closed upper low track
across the state, especially along and ahead of the occluding
surface front. MU CAPES expected to increase to around 1000 j/kg
today before tapering off later afternoon after the frontal
passage. The threat of widespread severe weather is low but an
isolated severe storm is possible with the marginal capes along
with rotational shear with the upper system tracking over.

Light showers will continue to taper off from southwest to
northeast tonight as the upper system departs northeast of the
area. Progs do divert on the rate of departing light showers, but
do agree with a bit more clouds around Friday due to either the
slower system, more clouds with the next s/w passing southwest of
the area, or a combination of both.

.LONG TERM...Friday Night Through Wednesday
Issued at 313 AM CDT Thu Aug 17 2017

A brief round of showers will be possible Saturday with a passing
shortwave. Additional thunderstorms will be possible as a low
pressure system passes Sunday evening to Tuesday morning before
dry conditions arrive ahead of the next 500 mb ridge.

A weak shortwave will move across central and southern Wisconsin
Saturday morning. Models have consistently trended dry for
northeastern Wisconsin, but wouldn`t be surprised if a small
chance of showers moves towards the Fox Valley in the next couple
days. Following this, dry conditions will be in place until the
warm front moves in Sunday night.

The warm front will be the initial focal point for convection and
active weather Sunday night. Better chances for some stronger
thunderstorms are currently expected further west towards
Minnesota. Upper level support appears weak at this time and
minimal low level jet is currently expected, so thunderstorm
strength is expected to be tied to diurnal heating, diminishing to
showers overnight into Monday. Rain chances will then continue
through most of Monday as a slow moving cold front moves through
the region, setting off another chance of showers and
thunderstorms for the area.

With these round of active weather through the area, drier
conditions move in Tuesday evening through the rest of next week
as northwesterly flow establishes itself and surface high pressure
builds in ahead of the next upper level ridge.

Temperatures will be above normal through the weekend before
settling closer to normal in the middle of next week.

.AVIATION...for 12Z TAF Issuance
Issued at 538 AM CDT Thu Aug 17 2017

A frontal system tracking over the area today will
produce scattered showers and isolated thunderstorms along with
widespread MVFR/IFR ceilings. The IFR ceilings with patchy MVFR
vsbys due to fog will mainly be located across northern Wisconsin.
The cyclonic flow will continue to produce a chance of showers
tonight, with mainly IFR ceilings across northern Wisconsin and
mainly a lower end MVFR ceiling elsewhere.

Beach Hazards Statement through this evening for WIZ022-040-050.


LONG TERM......Uhlmann
AVIATION.......TDH is the U.S. government's official web portal to all federal, state and local government web resources and services.