Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 140529
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1129 PM CST Wed Dec 13 2017

...AVIATION UPDATE...

.UPDATE...
Issued at 824 PM CST Wed Dec 13 2017

Winds are decreasing steadily between 7 and 8 PM, and this
continues through now. Thus the advisory has been allowed to
expire, after a day and evening of winds that frequently topped 50
mph. Of note, our 00Z upper air launch was successful, and we`re
proud of that, as winds were sustained at 39 mph gusting to 51
around the time of launch. That`s not easy! In any case, the main
questions for the rest of tonight and tomorrow are how the stratus
can clear/or not. There are a few subsidence channels of clearing
in the stratus to the north, but the over all expanse remains
widespread as of 830 PM.

&&

.SYNOPSIS...
Issued at 327 PM CST Wed Dec 13 2017

Deep 992 MB sfc low off passing clipper system noted currently acrs
southwestern LK MI ATTM, with deep pressure falls max acrs western
OH lighting the way of upper trof/wave. The passing deep clipper and
it`s tight cyclonic gradient with embedded pressure rise surges,
making for a monster wind machine acrs much of the region, some
enhanced gusts over 50 MPH this afternoon. After this system passes,
a chill down for the end of the week locally, but flattening out mid
CONUS pattern to bring about a warm up by Saturday. Then depending
on phasing of additional passing upper trofs, another weather system
possible in or near the local area Sunday into Monday.

&&

.SHORT TERM...(This Evening through Thursday)
ISSUED AT 327 PM CST Wed Dec 13 2017

Tonight...Will make a last minute call on the wind advisory for the
need of portions of it to be extended past the 00z Thu expiration
time, but am leaning toward letting it go as is for now. Still brisk
sub-advisory winds through at least 9 PM tonight, before gradient
continues to relax in wake of the clipper making it over OH by that
time. Cloud cover and a few embedded flurries wrapping down acrs the
area through mid evening, then subsidence rotating down out of
northern WI should bring about some clearing holes from the north
and northeast after 10-11 PM CST. Cold air advection from MN to
bring about low temps well down in the 20s by Thu morning, with some
upper teens possible under clearing holes and sfc wind drop off to
at least 5 MPH.

Thursday...Cloud cover a challenge, but will go with partly cloudy
with some clear areas in the morning from lingering subsidence, then
increasing clouds again from the north and west as the day
progresses. A low chance for some flurries in the far west and
northwest by late afternoon as the next upper trof rotates toward
the area out of the northern plains. Highs in the upper 20s in the
northeast, to the low to mid 30s in the southwest.   ..12..

.LONG TERM...(Thursday Night through next Wednesday)
ISSUED AT 327 PM CST Wed Dec 13 2017

Weak shortwave is on track to move across eastern Iowa Thursday
night, quickly exiting Friday morning. A few flurries or light snow
showers will be possible as it passes, otherwise look for partly to
mostly cloudy skies overall through the day with near normal
temperatures.

Above normal temperatures will return for the beginning of the
weekend as ridging builds across the Midwest and high pressure over
the Southeast U.S. provides warm southerly winds. Highs for Saturday
are expected to range from the upper 30s north to near 50 south,
which is around 10 degrees above normal (Normal highs are in the
upper 20s north to middle 30s south.)

The weather will turn more active beginning Saturday night as our
attention turns to the southern Great Plains. All models are in
agreement of a shortwave developing across northern Mexico and
southern Texas Saturday evening ahead of a deep trough in the
Western U.S. This shortwave is forecast to move quickly from Texas to
the western Ohio River Valley by Sunday afternoon, bringing chances
of light mixed precipitation to portions of the Mississippi River
Valley. Confidence on timing and precipitation type still remains
low at this time, so stayed tuned to later forecasts as this event
draws closer.

Behind this shortwave, northwesterly flow will return early next
week as high pressure builds across the central Great Plains.
Temperatures look to remain above normal.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday Night)
ISSUED AT 1124 PM CST Wed Dec 13 2017

MVFR stratus will be a concern through mid morning Thursday, but
increasing patches of clear skies will bring periods of VFR
weather through the night as well. Thus, a temporary cig is
forecast for northeast and east central Iowa sites. The clearing
hopefully will allow for any new stratocumulus to be VFR in
heights around 3500 to 5000 ft after mid morning Thursday. Winds
will be light north to northwest tonight into the morning, with
all sites seeing light west wind after mid morning.
ERVIN


&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

UPDATE...Ervin
SYNOPSIS...12
SHORT TERM...12
LONG TERM...Speck
AVIATION...Ervin



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