Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 211749
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1249 PM CDT Thu Sep 21 2017

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Friday
Issued at 340 AM CDT Thu Sep 21 2017

Convection trends today into Friday the first issue followed with
fog potential and then Friday afternoon max temps.

Early this morning, isolated showers and storms continue to
diminish over southeast Wisconsin as a cold front drops
southeastward. At 300 am the front pushed southeast of a line from
mtw to osh. Dense fog developed in the wake of the front across
parts of north central and central Wisconsin earlier overnight,
but drier air working into the area has eroded some of the fog in
the advisory area. With surface dewpoints lingering in the 60s
across northeast Wisconsin, potential of more fog early this
morning.

Surface high pressure settles into the north half of the state
today to push the front southward along with the better
instability. Bufkit data shows an increasing cap today due to the
warmer air 850 flow turns southwest during the morning. As a
result low level clouds and perhaps fog may be persistent across
parts of east central Wisconsin for at least this morning and
perhaps lingering into the afternoon.

MU cape values start low today but elevated cape levels increase
by tonight and a surface warm front lifts back north for a focus
of convection. Will keep the small chance pops tonight and Friday
morning as the warm front lifts northward. Its possible the
precipitation chances will start later this afternoon if the
instability and surface warm front make a quicker return. Progs
in good agreement with building elevated capes late this
afternoon as the 850 flow increases so will keep a small chance
over parts of central wisconsin and then lift this chance
northward tonight. Some potential of hail with the increasing
elevated instability and convection.

Decreasing clouds over central Wisconsin friday, following a warm
night and height 850 temps increasing to +20 will produce very
warm temperatures well into the 80s with a few lower 90s over
parts of central Wisconsin.

.LONG TERM...Friday Night Through Wednesday
Issued at 340 AM CDT Thu Sep 21 2017

The forecast period will start out with record or near record
warmth on Saturday and Sunday as 500mb ridge dominates the eastern
half of the United States with a deep trough across the western
United States. A major shift in the pattern will evolve next week
as western ridge develops across the western United States with a
downstream trough across the eastern half of the country. This
will mean an end to the record or near record warmth this weekend.
Temperatures will gradually return closer to normal by the latter
half of next week.

Shower and thunderstorm activity north and west of the area
could spill over into far northern Wisconsin at times through
Saturday through Sunday night. The evolution of the upper
pattern will be a slow process as Hurricane Maria slowly
moves up the coast well offshore the United States. This
will slow down the arrival of the cold front until next
week. Still some differences on when this will occur, but
current thinking is the best chance of showers and storms
will be on Tuesday as the cold front moves across the region.
Will still have a chance of showers and storms on Monday to
account for the GFS solution. High pressure will build into the
region for next Wednesday, bringing gusty northerly winds and
cooler temperatures.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1242 PM CDT Thu Sep 21 2017

Large patches of IFR/MVFR ceilings remained across the region at
midday, though VFR conditions were found over parts of northern
and east central WI. Latest satellite trends suggest that the
main area of stratus will continue to lift north this afternoon
and evening, resulting in improving flight conditions for all but
the RHI TAF site. The cold front that moved through the region
yesterday is expected to return north as a warm front later this
afternoon and tonight, and may produce isolated/scattered
thunderstorms. Confidence is only high enough to mention VCTS
in the TAFs at this time.

Have added LLWS to the RHI/AUW/CWA TAF sites from late evening
through early Friday morning, as low-level winds increase to
around 35 knots from the southwest.

&&

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

$$

SHORT TERM.....TDH
LONG TERM......Eckberg
AVIATION.......Kieckbusch


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