Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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048
FXUS63 KDVN 160012
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
612 PM CST Mon Jan 15 2018

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 330 PM CST Mon Jan 15 2018

The upper level low was evident on satellite imagery centered
roughly over far southeast MN early this afternoon. At the surface,
the departing low was over southern Lake MI. The tight surface
pressure gradient, cold air advection, and rounds of enhanced
forcing in the cyclonic flow aloft were combining to keep snow
showers, strong northwest winds and blowing and drifting snow over
all but the far southern tier counties of the forecast area.
Temperatures were mainly in the single digits, while wind chills
were in the single digits to teens below zero.

&&

.SHORT TERM...(This Evening through Tuesday)
ISSUED AT 330 PM CST Mon Jan 15 2018

Continued chances for light snow, blowing snow and bitter cold wind
chills are the forecast challenges. As the upper low begins to fill
into more of a negative tilted longwave trough over the forecast
area by Tuesday, there will continue to be support for at least
light precipitation over especially areas north of I-80 tonight.
There is an indication of a period of more focused isentropic lift
and moisture wrapping around the low level circulation spreading
into the north this evening, migrating south into the I-80 corridor
and southward, but generally weakening around sunrise Tuesday. Have
thus have increased pops for light snow tonight along these lines,
but for now have stayed below likely wording. Any snowfall should be
light, with perhaps amounts up to an inch possible in far northwest
IL this evening, in the axis of stronger upper level forcing.

Winds will remain brisk, but are expected to drop below the
sustained 20 to 25 mph range seen this afternoon to 15 mph this
evening and lose their gustyness and drop closer to 10 mph by
morning. This should eliminate the blowing snow threat by early
evening. With the extensive cloud cover returning to all areas this
evening, and the axis of coldest 850 mb temperatures passing well to
our southwest, temperatures do not look as cold as previously
indicated. Will have steady to slowly falling temperatures tonight,
with lows ranging from around 3 below in the west to 9 above in the
northeast. This will result in wind chills likely remaining above
our -20 advisory thresholds over most of our IL counties as well as
far eastern IA, while our western tier of IA counties and northeast
MO are on track to see roughly -20 to -23. With advisories already
out, will keep them in place to avoid confusion, but emphasize that
this appears to be a low end event.

Tuesday should see continued flurries and mostly cloudy skies.
Stayed near a guidance blend with highs around 10 to 20 from west to
east.

.LONG TERM...(Tuesday Night through Monday)
ISSUED AT 330 PM CST Mon Jan 15 2018

Tuesday Night through Thursday Night

Arctic high pressure in control through the middle of this week.
The center of the high is forecast to pass well to our southwest
across the Southern Plains, which will prevent the local area from
dropping well below zero Tuesday night. However, light NW winds
of 5-10 mph will yield wind chill values of 5 to 15 below zero
(warmer than the -20 F threshold for Wind Chill Advisory
criteria). Forecast high temps are in the 20s Wednesday, then jump
to the 30s for Thursday due to warm air advection from SW winds.
It will be breezy on Thursday with gusts of 20-30 mph possible
which could lead to areas of drifting snow where temps are below
freezing.

Friday and Saturday

Quiet and mild mid January weather on tap for the first part of
the weekend. Highs in the 30s and 40s with melt the majority of
the snow across the CWA. 850mb temps are forecast to peak above
10 C on Friday ahead of a backdoor cold front that should reach
the area on Saturday. Weak cold air advection will drop 850mb
temps into the lower single digits Celsius by Saturday night.

Saturday Night through Monday

The location of the backdoor cold front that is forecast to sag
southward into E Iowa/NW Illinois into Sunday morning will be a
key factor in determining the track of a possible sfc cyclone in
the Midwest from Sunday into next Monday.

All of the synoptic models have a lee-side low forming in the
Southern Plains and tracking to the NE as a Panhandle Hook along
a zone of low-level baroclinicity. Recent model trends have been
to shift the low track a little further to the SE. The
deterministic GFS is similar to its ensemble mean and is the
coldest of the synoptic models with a larger area across the CWA
receiving wintry precip. Even with a SE shift on the 12Z run, the
ECMWF is still warm enough for rain during the first part of this
storm. The CMC is in between the GFS/ECMWF low tracks. A lot can
change at this lead time, so it`s important to keep up with the
forecast through the week. Uttech

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
ISSUED AT 609 PM CST Mon Jan 15 2018

Light snow showers and flurries will continue rotating southward
tonight, impacting mainly KDBQ/KCID/KMLI. MVFR to brief IFR
conditions are likely in -SN. The snow will taper off after 12z
with ceilings improving to low VFR in the afternoon.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Wind Chill Advisory until noon CST Tuesday for Benton-Buchanan-
     Cedar-Clinton-Delaware-Des Moines-Dubuque-Henry IA-Iowa-
     Jackson-Jefferson-Johnson-Jones-Keokuk-Lee-Linn-Louisa-
     Muscatine-Scott-Van Buren-Washington.

IL...Wind Chill Advisory until noon CST Tuesday for Bureau-Hancock-
     Henderson-Henry IL-McDonough-Mercer-Putnam-Rock Island-
     Warren-Whiteside.

MO...Wind Chill Advisory until noon CST Tuesday for Clark-Scotland.

&&

$$

SYNOPSIS...Sheets
SHORT TERM...Sheets
LONG TERM...Uttech
AVIATION...RP Kinney



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