Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 100508
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1108 PM CST Sat Dec 9 2017

...AVIATION UPDATE...

.UPDATE...
Issued at 909 PM CST Sat Dec 9 2017

Evening update to add scattered flurries across the north
overnight. Recent radar trends to the north lend credence to
CAMS, which brush the north with some light returns near and after
midnight. Dry air in the low levels should preclude any
measurable snow. Also made some adjustments to temperature trends,
with clearing allowing for a quick drop in the northeast. This
will be tempered by increasing clouds and a southwest breeze
overnight.

&&

.SYNOPSIS...
Issued at 301 PM CST Sat Dec 9 2017

A clipper system in the northwest flow aloft was exiting the Great
Lakes this afternoon. Low level cold air advection and brisk north
to northwest winds in its wake were impacting the local forecast
area with temperatures in the upper 20s to lower 30s and wind chills
in the teens and 20s. Latest visible satellite imagery showed
thinning stratocu, but looming further upstream in the northwest
flow there was a stream of high cloudiness. Scattered flurries found
over much of the area earlier today were confined to isolated
pockets over northwest Illinois this afternoon.

&&

.SHORT TERM...(This Evening through Sunday)
ISSUED AT 301 PM CST Sat Dec 9 2017

Temperatures and cloud trends are the main challenges this period
under the active northwest flow. The next system, impacting mainly
the Great Lakes, will push a surface trough through early Sunday,
after a brief lull under a weak passing surface ridge tonight.

Tonight, dissipating low clouds should lead to mostly clear skies
early, then only thin high cloud cover through the rest of the
night. This, along with light winds and very dry air, should lead to
a quick drop into the upper teens to lower 20s over most of the area
in the evening. The rest of the night should see a more steady to
slowly falling trend due to increasing high clouds and light winds
that will be backing to the southwest ahead of the surface trough
toward morning.

Sunday, the surface trough pushes through early, leading to another
day of northwest winds, although not nearly as strong as today.
Models suggest low clouds will gradually fill in well behind the
front by afternoon, but overall, it looks to be at least partly
sunny, with the greatest potential for sunshine across the far
south. Have gone with highs there in the upper 30s to lower 40s,
while areas north of I-80 will likely be limited to the lower to mid
30s, close to blended model guidance.

.LONG TERM...(Sunday Night through Saturday)
ISSUED AT 301 PM CST Sat Dec 9 2017

Northwest flow aloft will lead to periodic chances for light
precipitation from clipper systems through Wednesday or Thursday of
this upcoming week. By Friday into next weekend, the 500mb flow is
forecast to become zonal, signaling a warm up.

Sunday Night and Monday

Precipitation Chances:

An Alberta Clipper is forecast to track through the Upper Midwest
into the Western Great Lakes late Sunday night into Monday morning.
Model consensus takes the sfc low either through E Iowa/NW Illinois
or just to the north. If this track holds, the stronger ascent and
higher snow amounts would fall in Wisconsin. For us, the current
forecast is a trace to a half inch across the far NE CWA, and
nothing further south. Any changes to the exact track of the low
would affect snow amounts, so stay tuned to forecast updates.

Temps:

The clipper will pull warmer low-level air northward, causing 850mb
temps to peak between 0 C to +4 C. Model blend sfc highs Monday
afternoon are in the mid/upper 40s south to mid 30s far north.
Although, some of the raw model guidance is colder - especially
across the north.

Tuesday and Wednesday

Coldest day of next week will be Tuesday when 850mb temps tumble
into the -12 C to -16 C range - forecast highs are in the lower 20s
NE to lower 30s far SW. Then warm air advection and a vorticity max
dropping southeastward in the NW flow aloft could bring light precip
Wednesday and Wednesday night. Forecast PoPs are relatively low
right now because the models are not in good agreement with respect
to the timing and track of this next system.

Thursday On...

Temps are forecast to moderate as 500mb heights over the Midwest
rise and the Western Ridge begins to flatten. The consensus model
blend has above normal temps by Friday and Saturday with mainly dry
conditions. Uttech

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday Night)
ISSUED AT 1106 PM CST Sat Dec 9 2017

A few flurries will be possible overnight at KDBQ but dry air in
the low levels should preclude any restrictions to visibility.
Otherwise, expect increasing mid clouds, followed by an increasing
nw wind Sunday and mainly MVFR ceilings.

&&

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

$$

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



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