Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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866
FXUS63 KDVN 071735
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1135 AM CST Wed Dec 7 2016

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 320 AM CST Wed Dec 7 2016

Midwest in grips of the leading edge of cold Canadian high pressure
system with lots of higher clouds to overspread the area today from
a passing upper air disturbance to our south. Temperatures are in the
upper teens north to 20s elsewhere with a brisk westerly wind of 10
to 20+ MPH with some gusts to around 25 MPH.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 320 AM CST Wed Dec 7 2016

Short term forecast confidence assessment...good or above average with
little sensible weather issues. Main issue is extent of clouds through
the period with some filtered sunshine possible. Temperatures should
be within 3 degrees of forecast highs with lows a bit more of a challenge
if low clouds timing is off.

Today...Cold and brisk with westerly winds of 10 to 20+ MPH and some
gusts over 25 MPH. Highs should range from the lower 20s north to the
lower 30s south under a mantle of high clouds and periods of filtered
sunshine possible.

Tonight...partial clearing and cold with main issue extent of lower
clouds to arrive from the northwest near or after midnight. Current
lows are based on mostly cloudy to cloudy skies mainly after midnight
and interpolating upstream what temperatures currently are. This supports
mostly guidance of lower teens north to upper teens south. Some risk
if skies clear for a period of time then mins may be need to be trimmed
by 3+ degrees for later shifts to reassess. Westerly winds to continue
at 15 to 25 MPH with wind chills near to below zero possible near sunrise.

.LONG TERM...(Thursday through Tuesday)
ISSUED AT 320 AM CST Wed Dec 7 2016

Active flow regime to continue through the long term with chances for
snow and cold air being the main headlines. The beginning of the period
will feature cyclonic flow aloft followed by northwest flow and a trof
moving through the area for the weekend. Then cooler temperatures for
next week with other chances of snow.

Thursday, as previously mentioned, cyclonic flow and steep llvl lapse
rates will lead to flurries across most of the area during the afternoon.
As previous shift has noted, there is saturation around - 10C, so ice
could be introduced into the column. Have kept them in the forecast.

Friday, guidance has come in dry for the potential WAA band of precip.
The best WAA looks to occur on Saturday when guidance introduces QPF
and pops back into the area. Latest iteration of guidance has removed
pops for Friday evening.

This weekend, all guidance suggests a system across the CWA that would
drop accumulating snow. Discrepancies between guidance exist in the
overall momentum fields and subsequent vorticity maxima and shape of
the forcing for the event. Confidence in strength of this potential
event is low at this time. The GFS and GEM suggest QPF ranging from
0.50 inches to 0.75 inches of liquid whereas the ECMWF is closer to
0.25 inches of QPF. Thermal profiles will be cold enough for all snow.
If guidance keeps on track for this system, headlines may be needed,
especially if convergence on a solution occurs. Pay attention to future
forecasts for this weekend.

Fresh snowpack along with cold H85 temps (depending on the model, GFS
-12 to -14C, ECM -22C, which seems anomalously low) will lead to cold
temperatures for the beginning of the week. This will set the stage
for a series of quick waves across the area where we could see additional
snowfall next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
ISSUED AT 1136 AM CST Wed Dec 7 2016

VFR conds this afternoon and evening with storm system`s well to
our north and south. Eventually, late tonight and into Thursday an
area of low stratus, ocnl MVFR cigs, will spread southward into
most of the TAF sites. Northwest to west winds around 15 knots
with gusts to 25 knots through most of the period.

&&

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

$$

SYNOPSIS...Nichols
SHORT TERM...Nichols
LONG TERM...Gibbs
AVIATION...Haase



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