Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 231650

Area Forecast Discussion
National Weather Service Green Bay WI
1150 AM CDT Sat Sep 23 2017

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Sunday
Issued at 255 AM CDT Sat Sep 23 2017

Focus for today through Sunday continue to be warm temperatures,
fog development and convection trends toward northwest Wisconsin.

Surface analysis shows a nearly stationary boundary over the Northern
Plains. Rounds of convection continue to track along and
northwest of this boundary under the southwest flow aloft regime.
A few of these storms may brush parts of northwest Wisconsin
during this period, including any convection developing along a
Lake Superior boundary, however the brunt of the convection
expected to be well northwest of the area for much of the weekend.

Boundary layer dewpoints in the 60s will provide some potential
of fog development for the overnight hours along with locations
along Lake Michigan. Early this morning, web cams and
observations indicate not enough development for any headline
issues at this time.

Many locations reached the lower 90s over central Wisconsin and
even some locations over northeast Wisconsin include Sturgeon Bay
and Oconto. First 90 degree or more high temp of the year reached
Friday at GRB as well. With plenty of sunshine and a warm start,
temperatures will make a similar run today and perhaps even for
Sunday. Lake and bay breeze was aided with an outflow boundary
Friday afternoon to cool temperatures late Friday afternoon. Will
see some cooling by the Lake and Bay this afternoon but should be
more local.

.LONG TERM...Sunday Night Through Friday
Issued at 255 AM CDT Sat Sep 23 2017

A pattern change is coming at the beginning of the period. The
500mb ridge is expected to shift east while a west northwest flow
pattern develops by the end of the upcoming workweek as a 500mb
ridge builds across the western United States with a resulting
downstream trough across the western Great Lakes region. High
temperatures in the 80s to around 90 will be replaced with highs
in the 50s and 60s. May also be looking at some frost late next
week into next weekend as well.

On Sunday night, cold front will slowly approach from the west.
Another unseasonably warm day is on tap Monday with highs in the
80s which will be some 15 to 25 degrees above normal. However,
there will be a chance of showers and thunderstorms, especially
across central and north-central Wisconsin. The front will then
gradually shift into the area Monday night and across the area
Tuesday. The best chance of showers and thunderstorms will be
across eastern Wisconsin will be on Tuesday. Tuesday could be an
interesting day with highs across the state ranging from the 50s
north to the middle 80s far southeast based on current timing of
the frontal passage on the ECMWF model. There will be a few
lingering showers tuesday night into Wednesday morning, but the
main story will be the temperatures returning closer to normal.

For the remainder of the forecast period, temperatures are
expected to continue to cool as western ridge builds. It is
possible that frost may become an issue Friday morning across the
north and next weekend across the entire area.

.AVIATION...for 18Z TAF Issuance
Issued at 1149 AM CDT Sat Sep 23 2017

Mainly VFR conditions to persist over the next 24 hours, other
than some patchy late night fog which could lower vsbys into the
MVFR range. The lake breeze has already passed through MTW with an
east-southeast wind through the afternoon. The rest of the region
will see steady southwest winds and unseasonably warm conditions
as high pressure remains parked to our east. Only thing to add was
adding some LLWS to the RHI TAF site for later tonight as winds
just above the surface could reach 30 knots.

Issued at 255 AM CDT Sat Sep 23 2017

Many locations across central and east-central Wisconsin reached
90 degrees on Friday, and for many was the first 90 degree
temperature of the year. On average the last 90 degree day of the
year usually occurs during the first half of August. The latest 90
degrees temperature on record during the year is: Green Bay 92 on
Sep 24 1891, Rhinelander 92 on Oct 1 1976 and Wausau 91 on Oct 1
1976. The latest 90 degree temperature reported across north-
central and northeast Wisconsin occurred on October 6th when
Hancock, New London, Waupaca and Suring hit 90 back in 1963.



LONG TERM......Eckberg
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