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000
FXUS63 KPAH 091207
AFDPAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
607 AM CST Mon Dec 9 2013

.UPDATE...
ISSUED AT 552 AM CST MON DEC 9 2013

FOR AVIATION SECTION ONLY.

&&

.SHORT TERM...(Today and Wednesday Night)
ISSUED AT 407 AM CST MON DEC 9 2013

For the very near term, allowed the Winter Weather Advisory for
Freezing Drizzle to expire at 3 am CST. A northeast to southwest
oriented mesoscale impulse (detected by KPAH/KVWX radars) sharpened
along the Ohio River around 07z Monday. Light freezing drizzle
occurred just ahead of it and very light snow developed with the
feature itself. Any residual lift in the slowly shallowing
boundary layer moisture will continue to wane through the morning
hours, insufficient to support an considerable production of
freezing drizzle.

Following the exit of this system, the leading edge of the next
weather system to impact part of the area will be moving into the
northern 1/3 to 1/2 of the area starting early this evening and
completely exiting the area by mid-morning on Tuesday.

The deterministic 00z Monday numerical model runs of the
GFS/ECMWF/GEM (Canadian) were consistent in the general placement
of this next narrow, west to east oriented, weather system. The
00z Monday 12km NAM-WRF was a little further north with this
system, but the 06z Monday model run is closer to the
aforementioned model solutions.

Although there is a slight potential for enhanced lift (implying
some banding of snow) with this system, it will likely not come
from any substantial negative EPV, since most of the forcing is
well above and out of phase with the preferred temperature levels
for the growth of ice crystals and accretion. However, the GFS
is most aggressive versus the GEM/ECMWF with respect to omega
around midnight tonight in the central sections (near I-57/route
13 intersection) of Southern Illinois. It is likely that between
05z-11z that the best forcing will generate a slightly more
efficient production of snow in roughly a 25-40 mile wide band
along a Benton to Mount Carmel Illinois line. At this time, this
is where the greatest new snowfall (roughly 1-1.5 inches) is
expected at this time.

Given the thresholds for advisory versus no advisory, as well as
the existing snowfall already on the ground at this time, will not
issue any advisory for snow at this time. In lieu of this
decision, will plan to highlight with a Special Weather Statement
(SPS) and mention in the Hazardous Weather Outlook (HWO) later
this morning.

The main uncertainty will be the degree of clearing this morning
and into early this afternoon ahead of this next system. The
combination of the departing lower cloud cover and the approaching
middle and higher cloud cover today may negate any meaningful
change in opaque cloud cover and temperature recovery over the
snow pack. The day shift may have to make short term adjustments to
account for these changes in cloud cover and resultant temperatures.

.LONG TERM...(Thursday through Sunday)
ISSUED AT 407 AM CST MON DEC 9 2013

Cold Canadian high pressure at the surface will be centered over the
region to start on Thursday. With snow still on the ground in most
areas, highs Thu will likely stay below freezing, despite ample
sunshine.

The next storm system will come in from the west later Friday and
esp Friday night. However, unlike the last big winter storm, the
cold dome of high pressure will be retreating to the east ahead of
this next system, allowing winds to turn more southerly in the lower
levels. This should allow for a decent warm up before the
precipitation arrives. Highs should finally make it well above
freezing Fri, then should not fall a great deal Friday night. Also
substantial warming will take place aloft with several thousand ft
of above freezing temps. Thus, this does not look like a snow/sleet
event at this time, but more like a cold rain in many locations.
There is some potential that areas with deep snow cover could see
sfc temps drop back down to near freezing Friday night, so will
allow for rain or freezing rain in those locations. This would
mainly be in areas of sw IN and along/north of rt 13 in srn IL.

The system should exit early Sat, and the remainder of the weekend
looks to be mainly precip free and chilly as another area of high

&&

.AVIATION...
ISSUED AT 1120 PM CST SUN DEC 8 2013

MVFR cigs should clear out by around 18z, leaving VFR conds until
a quick moving upper level trof brings another shot of MVFR
conditions and possible a touch of snow into the KEVV/KOWB sites
aft 06z tonight. Vsbys may be reduced to around 5SM at times
during any snow.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
MO...NONE.
IN...NONE.
KY...NONE.
&&

$$

UPDATE...GM
SHORT TERM...Smith
LONG TERM...GM