Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 260820
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
320 AM CDT Tue Sep 26 2017

Forecast discussion for routine morning forecast issuance

.SHORT TERM...Today...Tonight...and Wednesday
Issued at 318 AM CDT Tue Sep 26 2017

Although the precise location was hard to discern, a cold front
appeared to bisect the forecast area from central WI into
northeast WI early this morning. Radar indicated scattered showers
along and behind the cold front, though much more widespread
rain was occurring over the eastern Dakotas, MN and western IA,
closer to dynamic support from a large upper trof and the RRQ of
a strong upper jet. Moisture was plentiful, with PWATs of
1.50-1.75 inches near and behind the boundary. A weak surface
low was lifting northeast through far southeast MN and northeast
IA, along the frontal boundary.

Showers will increase across the region as the surface low
deepens and lifts northeast through WI, and drags the cold front
through the forecast area. Will carry likely pops across the
forecast area, with showers decreasing from west to east during
the late afternoon and early evening. Instability will be very
marginal, so will only mention isolated thunderstorms today.
Temperatures will vary significantly across the region, with
highs ranging from the mid to upper 60s in north central WI to
around 80 southeast.

Expecting mainly dry conditions later tonight into Wednesday,
with a gradual decrease in clouds during the period. The most
substantial change will be a return to normal or slightly below
normal temperatures. Lows tonight will be in the 40s to lower
50s, with highs on Wednesday in the upper 50s to middle 60s.

.LONG TERM...Wednesday Night Through Monday
Issued at 318 AM CDT Tue Sep 26 2017

The latest GFS ensemble mean indicates a general deamplification
of the upper air pattern over the next week. After a brief cool
down later this week, guidance indicates that above normal mid-
level heights will return to the western Great Lakes.

Wednesday night through Thursday night...Flattened troughing will be
present overhead on Wednesday night.  If there are any weak
shortwaves moving through, high pressure at the surface and ample
dry air should prohibit precip.  Better chances of showers will
arrive on Thursday into Thursday night when a fairly robust
shortwave dives southeast into the region.  Highest precip chances
look to occur over northern WI.  Temps will be seasonable over the
period.

Rest of the forecast...Clouds and scattered showers will likely
linger into Friday morning over northern WI.  Then clearing should
occur on Friday afternoon into Friday evening.  Friday looks to be
the coolest day over the next week.  High pressure will then
reassert itself for next weekend, which looks mainly dry and
comfortable.  The next chance of precip will occur with the next
frontal passage early next week.  Early indications are that temps,
in general, look to be above normal for much of next week.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1047 PM CDT Mon Sep 25 2017

An approaching cold front will bring an increased chance for
showers and thunderstorms during the TAF period as it slowly
tracks east through the western Great Lakes. The best chance for
thunderstorms will be Tuesday afternoon, save for RHI where there
will be less instability. Otherwise showers are mainly expected
as this front moves to the east. The eastern TAF sites should stay
dry until later tonight or early Tuesday morning given the later
arrival of the front. Conditions are expected to drop to MVFR,
with IFR possible as the front moves through. Behind the front
conditions are expected to remain at MVFR as winds turn to the
west later Tuesday afternoon and into Tuesday evening.
&&

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

$$

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


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