Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 171926
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
226 PM CDT Sat Jun 17 2017

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Sunday
Issued at 226 PM CDT Sat Jun 17 2017

The latest RAP analysis and satellite/radar imagery show a weak
cold front/surface trough positioned over eastern WI early this
afternoon. Cu has been building through the day along the front,
and wouldnt be surprised to see a few showers pop up. Cu is more
robust over northern WI and the Upper Peninsula, where showers
appear to be a slightly better bet though. Looking to the west,
showers and thunderstorms are popping along a cold front over
northern Minnesota. Scattered showers and storms are also pushing
east over the northern Plains ahead of a potent shortwave trough.
As this trough moves east across the region tonight, precip trends
are the main forecast concern.

Tonight...The strong shortwave trough will continue to move east
and into the region late this evening and overnight. Meanwhile,
the cold front over Minnesota will slide southeast into northern
WI late tonight. Lingering daytime instability may still
contribute to isolated showers/storms over northern WI early in
the evening. But the latest short term guidance indicates that
more widespread shower and isolated thunderstorms will push into
central and north-central WI from the west by 02-04z. Elevated
instability by this time will be up to 500 j/kg, so think severe
chances are very low. Track of the shortwave and associated
deformation zone will call for the heaviest precip north and west
of the Fox Valley late tonight. Amounts could reach up to an inch
over north-central WI, which will exacerbate the higher water
levels on area rivers. Precip does not appear to make it into
eastern WI until after midnight, and should be considerably less
than areas to the northwest. Low temps ranging from the mid 50s
north to low to mid 60s south.

Sunday...The shortwave will swing northeast across the area during
the morning before exiting in the afternoon. Widespread rain will
be ongoing across northern WI for much of the morning before
exiting early in the afternoon. However, a trailing shortwave
interacting with minor instability could still lead to scattered
showers during the rest of the afternoon over much of the area.
Much cooler highs ranging from the mid 60s to mid 70s.

.LONG TERM...Sunday Night Through Saturday
Issued at 226 PM CDT Sat Jun 17 2017

The long term will feature off and on showers and thunderstorm
chances as the Great Lakes region remains in a NW flow regime,
with waves of energy rotating around the upper trough over eastern
Ontario. Hard to time the best chances for precip, so will
continue to feature chance or slight chance POPs from Sunday night
through Tuesday. Models showing the upper pattern becoming more
zonal on Wednesday, with brief ridging building over the western
Great Lakes, which looks to provide the best chance for a dry day.
However, models showing a wave crossing near the Canadian border
that could touch of an area of showers and storms later on
Wednesday. Again, timing these features this far out is a
challenge, but will try to get at least a couple dry periods
Tuesday night into Wednesday, then bring back chances for
rain/storms on Wednesday into Wednesday night.

Northwest flow will keep temps below normal through mid-week then
near or slightly above normal temps should return toward the end
of the week.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1138 AM CDT Sat Jun 17 2017

VFR conditions and generally quiet weather are anticipated across
the region this afternoon, with only isolated showers/storms along
the Lake Michigan lake breeze, and also over north-central WI.
Showers and scattered thunderstorms will increase across the
region by mid to late evening, as a strong upper level
disturbance moves through. Ceilings are expected to lower to
MVFR/IFR over north central and central WI late, and visibilities
will be reduced at times due to steadier/heavier rainfall.
&&

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

$$

SHORT TERM.....MPC
LONG TERM......Bersch
AVIATION.......MPC



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