Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 240547

1147 PM CST Tue Dec 23 2014

Issued at 1139 PM CST TUE DEC 23 2014

For aviation section only.

UPDATE Issued at 857 PM CST TUE DEC 23 2014

Primary adjustments made to first period (tonight) and secondary
adjustments to second period (Wednesday) to reflect higher
resolution changes in PoP, Weather, and other sensible weather
grids down to an hourly basis.

Transition currently in place moving primary deformation zone
from northwest Missouri, eastward toward eastern Missouri later
tonight. Main trigger for the transition was noted over northeast
Texas near the base of a sharpening positively tilted trough. As
the main vorticity center and lift shifts across Southeast
Missouri/East Central Missouri/Southwest Illinois through the 10z-
17z Wednesday time frame, best lift (omega) associated with
maximum dendritic snow growth shifts from Southeast Missouri into
Southern Illinois after 8 am CST. Utilized a rain/snow mix over
the Southeast Missouri foothills through mid-morning, then
shifting this wintry mix over Southwest Illinois, mainly along and
west of the I-57/i-64 corridor through Noon. A brief mix then
stretches across the I-64 corridor through early afternoon.
Snowfall amounts will still remain quite minimal, given the
antecedent ground/pavement/ambient air temperatures preceding the
dynamic lift associated with the northeast ejecting trough/low.

Little significant changes to temperatures and dewpoints. Some
moderate changes made to wind, wind gusts, and minor tweaks to any
snowfall coverage for Wednesday.


.SHORT TERM...(Tonight through Thursday night)
Issued at 247 PM CST TUE DEC 23 2014

Medium confidence in Christmas Eve forecast with models still not in
the best agreement, especially where QPF and critical thicknesses
are concerned.

As a sharp H5 trough lifts northeast out of the central plains
tonight, it will induce a surface low/wave on the front and bring
another surge of moisture and increased precipitation chances back
across the region overnight.

The forecast for Christmas Eve is still a bit tricky due to
discrepancies between model QPF, critical thicknesses, and timing.
On Christmas Eve an area of moisture/wrap around precipitation
(deformation zone) will be pulled across the area with the
surface/upper low couplet. In the process, the deeper cold air will
begin to filter into the region mainly in the afternoon, albeit a
tad slower than models were showing yesterday.

The down side to any snow accumulation will be the antecedent
conditions where temperatures are concerned, ie the ground and
roadways are and will be fairly warm at the onset of snow. Long
story short, have light snow amounts over our far western counties
Wednesday morning, then less than an inch generally north and west
of a line from Fairfield Illinois to Greenville Missouri Wednesday
afternoon. As the last of the moisture/wrap around QPF exits the
region Wednesday night, there could be minor snow accumulations
generally north and east of a line from Mount Vernon Illinois to
Calhoun Kentucky.

Unfortunately for those individuals wishing for a white Christmas in
areas other than the ones mentioned above, it`s not looking good for
the home team. Maybe next year.

.LONG TERM...(Friday through Tuesday)
Issued at 247 PM CST TUE DEC 23 2014

High pressure over the southeast U.S. will give us dry conditions
Friday along with southerly winds.  The south winds along with some
sunshine will help temperatures climb into the lower 50s, with lows
Friday night only dropping into the lower 40s.

GFS brings a cold front across the middle Mississippi and lower Ohio
valleys Friday night, while ECMWF is much slower and brings the
front through Saturday night.  The GEM solution is much closer to
the ECMWF solution, so prefer to lean toward the slower passage.
Unfortunately this lends itself to a fairly wet weekend overall.
Surface temperatures and forecast soundings indicate we should
remain all rain Friday night and Saturday.  Based on the slower
frontal passage, colder air will be slower to infiltrate the PAH
forecast area, which will keep rain from mixing with snow as quickly
Saturday night, and the mixed precip should be confined to our
northwest half of counties.  This should keep any snow accumulations
to a couple of tenths at best in these area.

By Sunday, high temperatures are expected to be well above freezing
across most of our counties, so the rain/snow mix should continue to
be confined to portions of southern Illinois and southeast Missouri.
Precipitation will be tapering off Sunday night, and should end as
light snow or a rain/snow mix.  No accumulations are expected.

Dry conditions are expected Monday into Tuesday with a weak surface
high over the central/south central U.S.  Northwest winds will keep
temperatures a little below seasonal normals.


Issued at 1139 PM CST TUE DEC 23 2014

MVFR cigs should prevail through 15-17z Wed KCGI/KPAH. IFR/Low IFR
conditions expected KOWB/KEVV. Some improvement is expected by
17-18z as a cold front moves east of the region. Still, will
likely keep MVFR cigs north/eastern sites much of the TAF period.




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