Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 151139
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
539 AM CST Fri Dec 15 2017

...12Z AVIATION UPDATE...

.SYNOPSIS...
Issued at 343 AM CST Fri Dec 15 2017

A weak surface trough from central WI southwest bisecting Iowa was
triggering a few flurries as it was pushing southeast across the
forecast area early this morning. Further west, the precipitation
has been falling as flurries and light freezing drizzle in central
Iowa, where it has created some ice covered roads. A weak impulse in
the northwest flow aloft was triggering another area flurries across
southern MN, southwest WI into northeast Iowa. Widespread cloud
cover and southwest to northwest shifting winds around 10 mph were
holding temperatures in the mid 20s.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 343 AM CST Fri Dec 15 2017

Main focus is on cloud trends, flurries and impacts on temperatures
today and tonight. The low clouds, covering much of the upper MS
valley and northern plains will continue to blanket the area through
at least the morning hours. Flurries will be exiting the south with
the advancing surface trough this morning, but will likely see
additional rounds of flurries across mainly the north into the
afternoon. Conditions will become more favorable for the clearing of
the cloud cover from southwest to northeast from at least mid
afternoon through tonight as the flow aloft begins to become more
westerly, nudging the stream of moisture trapped below the inversion
eastward. Afternoon sunshine developing low level warm air advection
should push temperatures into the lower 40s in the southwest half of
the forecast area. Low clouds lingering in the northeast, along with
flurries, will likely hold highs to the lower 30s there.

Tonight, there could be lingering flurries from additional weak
impulses over the northeast in the evening. Otherwise, the cloud
cover should thin out overnight. South to southwest surface winds
ahead of the next clipper system moving into the upper MS valley
will prevent any sharp temperature drop and thus stayed with
guidance lows from the mid 20s north to around 30 south.

.LONG TERM...(Saturday through Thursday)
ISSUED AT 343 AM CST Fri Dec 15 2017

Saturday and Sunday

Mild to start the weekend with around 40 F far north to the lower
50s far south for Saturday`s highs. A sfc pressure trough is
forecast to slowly drift into E Iowa/NW Illinois Saturday night into
Sunday morning, setting up a light convergent flow across
approximately the northern half of the CWA. This could result in
areas of fog as the NAM is indicating, but have low confidence at
this lead time.

Forecast soundings show top down saturation on Sunday in response to
steady moisture advection via SW flow aloft. Additionally, a
shortwave emanating from the Southwest Plains will ride through the
Midwest, providing a period of weak ascent and chance for light
precipitation. Most models have QPF of less than 0.10 inches and
favor the southern half of the CWA. The CMC is a wet outlier with up
to 0.30 inches and has QPF across the entire forecast area.

Thermal profiles support mainly rain, possibly mixed with snow on
the northern edge of the precip shield. The threat for freezing rain
is very low due to warm sfc wetbulb temps.

For Sunday night, the NAM/CMC have areas of drizzle and the NAM
drops temps to near or below freezing. Right now, confidence is low
on the occurrence of drizzle or freezing drizzle but it`s something
that will have to be monitored.

Monday through Wednesday

Zonal mid-level flow brings mild and dry weather with highs
averaging in the upper 30s far north to the upper 40s far south.

Thursday

Models have a sfc low developing in the Midwest. The consensus track
at this time is far enough north to give us rain initially. Then
possibly a changeover to snow on the backside. It is too far away to
get much into the details. Uttech

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday Morning)
ISSUED AT 539 AM CST Fri Dec 15 2017

Low clouds, at times with MVFR ceilings, will linger through most
of today. A few very light snow flurries will continue this
morning over all the terminals, and then will be possible this
afternoon, especially at DBQ. These are not expected to have any
impact and for now are only mentioned at the DBQ site for this
morning. Prevailing VFR conditions are expected for tonight with
surface winds turning to the south.

&&

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

$$

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


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