Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 161142

Area Forecast Discussion
National Weather Service Green Bay WI
642 AM CDT Fri Jun 16 2017

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Saturday
Issued at 348 AM CDT Fri Jun 16 2017

Precipitation trends will be the main forecast concern.

A short-wave trof was moving through the forecast area early this
morning, and producing a small cluster of showers and thunderstorms
over the central part of the forecast area. This precipitation
should be east of the region by 12z, and the rest of the morning
should be dry. Addition weak short-wave energy may arrive for the
afternoon, and should help trigger scattered showers and storms,
especially in far northeast WI (weak surface trof), and possibly
in central WI (weak boundary). With CAPE around 1000 j/kg and
strong deep layer shear, there could be isolated strong storms.
Used a blend of the better performing models for max temps, which
should be mostly in the lower to middle 80s.

Forcing will increase tonight, as the LFQ of an upper level jet
arrives and H8 WAA increases. Not confident enough in the trends
to go above mid-range pops at this time, but several models
produce moderate QPF over the southeast half to two-thirds of
GRB CWA, so pops may need to be raised with subsequent forecasts.
Lows should range from the middle to upper 50s northwest to the
lower to middle 60s southeast.

On Saturday, a weak cold front will shift into the region.
Cyclogenesis may occur along the boundary late in the day, as
short-wave energy and the RRQ of an upper jet arrive. Models
are showing a split in the main precipitation areas, with higher
amounts over our northwest and southeast counties, and less in
between. Once again, will only go with mid-range pops until
trends become clearer. The severe weather threat looks lower than
it did 24 hours ago, but a marginal risk remains over the Fox
Valley and part of the lakeshore region, where CAPE may reach
1000-1500 j/kg in the afternoon. Abundant cloud cover should
result in slightly cooler temperatures, with highs in the upper
70s and lower 80s.

.LONG TERM...Saturday Night Through Thursday
Issued at 348 AM CDT Fri Jun 16 2017

Multiple mid level short waves moving through the region in a
broad trough will bring chances for showers and thunderstorms at
times over the weekend and into the early part of next week.
Tuesday night into Wednesday evening currently looks like the
best chance for a period of dry weather with surface high pressure
over the Great Lakes and an approaching low amplitude ridge
aloft. Flow aloft then starts to back and another surface system
makes its way toward the area, bringing more chances for showers
and storms later Wednesday night and on Thursday.

Saturday night severe potential looks more questionable than it
did at the same time last night. 00Z models had higher MUCAPE and
bulk shear values confined to the southern half of Wisconsin, and
the 05Z edition of the SPC day 2 outlook only had marginal risk
across the far southern part of the forecast area.

Below normal high temperatures are expected during the active part
of the forecast, with plenty of 60s and lower 70s Sunday and
Monday. A warming trend starts on Tuesday, and near highs should
be near normal at most locations for Wednesday and Thursday.

.AVIATION...for 12Z TAF Issuance
Issued at 633 AM CDT Fri Jun 16 2017

A small cluster of showers and thunderstorms will exit far
northeast WI early in the TAF period. Isolated to scattered
showers and storms should redevelop as instability builds
during the afternoon. The best chance of showers is expected
this evening into the early overnight hours as upper level
forcing increases. Have added TEMPO groups to the TAFs for
the most likely period of showers, but will hold off on
adding thunder at this time. After the showers taper off
later tonight, some patchy low ceilings or fog may develop.




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