Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 130533
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1133 PM CST Fri Jan 12 2018

...06z AVIATION UPDATE...

.UPDATE...
Issued at 904 PM CST Fri Jan 12 2018

Mid level cloudiness attendant to passing wave will move across
western and southern portions of the cwa overnight into Sat AM,
mainly from Cedar Rapids to Galesburg on southward. As a result,
I have nudged up lows a few degrees in much of this area,
especially heading further south/west, as locations on the
northern edge will likely see a shorter residence time in the
thicker cloud cover. Otherwise, wind chill advisory remains in
effect for portions of northeast IA within the fresh snow cover
where chills will be around 20 below zero at times tonight.

&&

.SYNOPSIS...
Issued at 325 PM CST Fri Jan 12 2018

Latest MSAS analysis indicates 1043 MB ridge axis draped acrs the
northern plains down acrs the MO RVR Valley, with lee side pressure
gradient maintaining acrs the mid and upper MS RVR Valley with brisk
afternoon winds. Cold core L/W trof was occupying much of the
central into eastern CONUS, while an embedded wave was getting
booted up the OH RVR Valley. Weak secondary vort aloft combining
with some LLVL instability, was/is producing stratocu rows/decks with
embedded flurries or even light snow showers generally along and
east of the MS RVR currently... ending acrs NW IL. Cold Canadian
regime still on track for the weekend and into early next week, with
a Sunday night clipper system to deal with.

&&

.SHORT TERM...(This Evening through Saturday)
ISSUED AT 325 PM CST Fri Jan 12 2018

Tonight...The CU fields with embedded flurries/light snow showers
should continue to decrease from north to south into the early
evening with passing wave and ending sunshine. Then clear skies for
awhile this evening, before a portion of upstream higher based
stratocu deck acrs the plains tries to stream east-southeast over
the southwest 2/3`s to half of the DVN CWA overnight into Sat
morning. Incoming ridge gradient will keep mixing sfc winds of 10-15
MPH going overnight, and combined with the cloud blanket will
prevent a complete temp bottom out acrs much of the area. But the
northern third should stay mainly clear, and with below zero ambient
temps north of I80 and west of the MS RVR. Will go with a Wind Chill
Advisory after midnight and into Sat morning for the higher
snow/icepack areas of Benton, Buchanan, and Delaware counties. It
may be a bit marginal but getting values of around 20 below late
tonight early Sat morning in those areas, if ambient temps can get
close to -4 to -7 or so. Overnight lows will look to range from
around 5 above in the south under the cloud blanket, to the
mentioned 4-7 below in the northwestern quarter of the CWA.

Saturday...1040+ MB strong cold dense sfc ridge axis on track to
slide eastward toward  the mid and upper MS RVR Valley through Sat
evening. Bitter wind chills will continue acrs much of the CWA
through at least late morning, while lingering cloud cover thins out
of the southern CWA. Frigid start northwestern third of the CWA may
have trouble getting out of the upper single digits even with
insolation, while the southeastern half makes it into the low to mid
teens.   ..12..

.LONG TERM...(Saturday Night through next Friday)
ISSUED AT 325 PM CST Fri Jan 12 2018

The main forecast issues in the long term period are the clipper
system Sunday, with blowing/drifting snow and plummeting wind chills
to follow Monday.

Saturday night: Surface high pressure will be overhead with very
cold conditions but winds not strong enough to warrant more wind
chill headlines.

Sunday: Southerly winds will provide a modest warm-up into the teens
and 20s ahead of a vigorous clipper system that will bring
accumulating snow to most if not all of the forecast area. Initial
WAA snow is expected to begin Sunday afternoon, mainly west of the
Mississippi River. The bulk of the moisture and forcing will arrive
Sunday night. WPC snow-to-liquid ratios of 15-19:1 look more
reasonable based on Bufkit output and the lack of any slam dunk
DGZ/Omega bullseye. These ratios, combined with blended QPF of 0.05
to 0.15 inches, yields snow amounts mainly in the 1 to 3 inch range.
Higher amounts are favored north of Interstate 80. The wind will
begin to pick up across the west late Sunday night, with some
blowing and drifting snow expected in open areas.

Monday-Tuesday: Snow will taper off in the east Monday morning. The
big issue will be a northwest breeze gusting around 30 to 35 mph.
The highest accumulations of light, fluffy snow, combined with the
higher wind speeds, favor locations north of I-80 in eastern Iowa
for the more widespread blowing and drifting. If current trends
continue, headlines for the combined impacts of snow/blowing snow
would be forthcoming over the weekend. Bitterly cold wind chills
will also develop Monday through Tuesday morning, with values easily
in the advisory range, and possibly in warning criteria across the
far west.

Wednesday-Friday: Expect a return to zonal flow with warming temps
and dry conditions through the period.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday Night)
ISSUED AT 1129 PM CST Fri Jan 12 2018

Conditions will remain VFR through the TAF cycle. Winds will be
northerly at around 10 kts and locally gusty into Saturday then
become light by Saturday evening as high pressure begins to move
in.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Wind Chill Advisory until 9 AM CST Saturday for Benton-Buchanan-
     Delaware.

IL...NONE.
MO...NONE.
&&

$$

UPDATE...McClure
SYNOPSIS...12
SHORT TERM...12
LONG TERM...RP Kinney
AVIATION...McClure



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