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fxus63 kdvn 141747 
afddvn

Area forecast discussion
National Weather Service Quad Cities Iowa Illinois
1147 am CST Sat Dec 14 2019

..aviation update...

Update...
issued at 858 am CST Sat Dec 14 2019

Have updated sky grids to go more pessimistic on cloud cover as
strong inversion at 924 mb seen on kdvn 12z/14 sounding trapping
low clouds. In addition decent cold air advection taking place. In
fact, visible satellite shows extensive low clouds throughout
Iowa and into eastern Minnesota. You have to go into far NW Iowa/western
Minnesota and eastern Dakotas to find sunny skies.

Models insist on gradual clearing this afternoon from west to east
but will monitor the trends and update if needed.

&&

Synopsis...
issued at 335 am CST Sat Dec 14 2019

A cold front continues to move slowly to our south and east across
central Illinois and northern Missouri. A disturbance passing along
the front had some light precipitation falling across northern
Missouri but just outside of Clark and Scotland counties early this
morning. Widespread low clouds are in place across the area with
temperatures ranging from mid 20s northwest of Cedar Rapids to the
mid 30s across far southeast Iowa, west central Illinois and far
northeast Missouri. There is widespread haze across the area
producing visibilities between 3 to 5 miles.

&&

Short term...(today and tonight)
issued at 335 am CST Sat Dec 14 2019

The main forecast concerns today will be clouds and temperatures.
Models are in good overall agreement.

The cold front and storm system will move into the middle Ohio River
valley during the day on Saturday as high pressure builds into the
eastern Dakotas by midday with colder and dryer air flooding into
the area. High temperatures will occur this morning with
temperatures falling through the remainder of the day. In addition
to the falling temperatures, there will be breezy northwesterly winds
through the day of 10 to 20 miles per hour. This will make it feel like
temperatures are in the teens for much of the day.

High pressure is forecast to sink into southwestern Minnesota and
northwest Iowa by 12 UTC Sunday. Temperatures will be very cold
Sunday morning with lows in the upper single digits northwest of a
Cedar Rapids to Dubuque line and the upper teens across far
southeast Iowa, west central Illinois,and far northeast Missouri.
Winds will be lighter by then but the coldest wind chills Sunday
morning will be in the single digits to near zero along the Highway
20 corridor.

Low clouds will linger through into the late morning before slowly
moving out of the area from west to east after 18 UTC. Model
soundings as well as model 925 relative humidity support this idea. There may be
some lingering clouds across far northwest Illinois. Clouds will
then slowly increase after 06 UTC as the next storm system
approaches.

Long term...(sunday through friday)
issued at 335 am CST Sat Dec 14 2019

Sunday and Monday

Overview:

A positively tilted trough will cross through The Four Corners on
Sunday and then emerge into the Central Plains and mid Mississippi
Valley on Monday. Models are in good agreement on the mid-level
trough axis maintaining a slight positive tilt through the central
U.S. This trough will be accompanied by a weak, elongated area of
surface low pressure (1008 mb) that will track through Tennessee and
Kentucky.

Snow timing:

Light snow will develop over Kansas and Missouri Sunday morning in a
zone of 700mb warm air advection and convergence. The ascent and
area of light snow will move into parts of eastern Iowa and
northwest Illinois later Sunday afternoon and evening. Periods of
light snow are possible through Monday afternoon, especially across
the southern County Warning Area.

Snow amounts:

Latest forecast snowfall ranges from around 1" close to I-80 to 2-4"
in the counties along and south of Highway 34. The highest amounts
are across the southern tier of counties where isolated amounts near
5 inches are possible, but this is over an 18-24 hour period.
Confidence is low on amounts exceeding 4 inches at this time. The
highest probabilities for 2" or more of snow (50-60%+ is south of a
line from Princeton, Illinois to Fairfield, Iowa.

This continues to look like a longer duration event with periods of
light snow, and possibly some breaks at times. For that reason, and
since winds will be fairly light at 10-20 mph, thinking a Winter
Weather Advisory may be needed at some point across the south as
opposed to a watch or warning.

Confidence is moderate to high on light snow impacting the southern
cwa, but low on exact amounts and on the northern extent of the
light accumulations. Models have come into better agreement with the
00z/Sunday runs. The current forecast reflects the most likely
outcome at this stage, which didn't change much from the Friday
afternoon update. If anything, it's slightly lower in places by a
half inch to 1 inch. The band of snow could still shift north or
south a bit which would affect forecast snowfall amounts.

Tuesday on

Dry and quiet weather is expected next week with highs moderating
into the 30s and 40s. Uttech

&&

Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 1145 am CST Sat Dec 14 2019

Widespread MVFR cigs through this afternoon then becoming VFR as
high pressure gradually builds into the area from the northern
plains. Northwest winds 10 to 15 knots this afternoon then less
than 10 knots tonight into Sunday morning.

&&

Dvn watches/warnings/advisories...
Iowa...none.
Illinois...none.
MO...none.
&&

$$

Update...haase

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