000
FXUS63 KPAH 131018
AFDPAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
418 AM CST Fri Dec 13 2013

.SHORT TERM...(Today and Sunday)
ISSUED AT 418 AM CST FRI DEC 13 2013

Running way behind this morning, so will try to be brief. The only
change to the Advisory was to push the onset of the western
portion of it back to 18Z. This was done largely because there is
no QPF before 18Z anywhere in our area. Confidence is quite low in
the Advisory at this time, especially the southeastward extent of
it.

The 00Z models have slowed down significantly with the first
little band of precipitation that was to lift northeast across at
least southeast Missouri and southern Illinois. It now will not
reach the far west until after 18Z, and the southeast extent of
this precipitation is in doubt. The 06Z NAM actually keeps it
mostly northwest of our area. With the initial precipitation, due
to the extremely dry air in the low-levels, it could be anything
from snow to sleet to rain. The good thing about the later onset
is that it will likely be above freezing before the precipitation
starts, which should prevent any icing this afternoon. Kept the
Advisory going this afternoon, due to the potential for a brief
period of sleet or snow to cause some minor travel issues.

As for tonight, used a consensus of all MOS and raw model output
we have in our system to come up with the hourly temperature trace
today through Saturday. This basically keeps the entire area above
freezing for the duration of the event. The 21Z and 03Z SREF
probabilities indicate that there is virtually no chance of
freezing temperatures at the surface for the duration of the
event. Areas near Pinckneyville and Mt Vernon Illinois may be
right near freezing, but for the most part, its gonna take
significant snowfall rates to accumulate and bring the temperature
down to near freezing tonight and early Saturday. This will be
possible in those same northwestern areas, if a decent deformation
zone can develop. The bottom line is that freezing rain/icing is
not expected.

Model soundings except in the far northwest support rain or snow
across much of the area this evening. The soundings climb above
freezing near the surface, so it may or may not be able to melt
fully before reaching the ground. Along the northwest fringe of the
area, pure snow is a real possibility. Heading into the overnight
hours, the precipitation will become all rain in the far southeast
first and then spread north and west across much of the southern
half of the area toward morning. Meanwhile the pure snow area will
gradually shift eastward along I-64 toward morning. Using mostly
HPC QPF and a 8:1 snow to liquid ratio, came up with 2-4" along
I-64 and the northwest fringe of the area. Used the lower ratio
even with pure snow due to the uncertainties in the surface
temperatures and intensity of the snowfall. Still feel that the
QPF may be overdone. There may be a very sharp gradient in
snowfall to the southeast of that area.

All in all this is a very low confidence forecast.

.LONG TERM...(Sunday Night through Thursday)
ISSUED AT 418 AM CST FRI DEC 13 2013

Much of the extended portion of the forecast continues to look dry
and uneventful. The mean position of a longwave trough over the
eastern U.S. will keep the forecast area in northwest flow aloft
through at least Tuesday. As a result, temperatures will remain
below normal to start the week. The coldest period of the extended
will be Sunday night, when lows are forecast in the upper teens to
lower 20s.

High pressure at the surface will begin to shift east of the area
early in the work week. This will result in a gradual moderation in
temperatures through mid week. Any leftover snowpack will of course
temper the warm-up early on. However, a transition to southwest flow
on Wednesday should result in substantially warmer readings by
Thursday. In fact, highs may be pushing the 50 degree mark in some
locations by Thursday. An approaching weather system will bring our
next chance of rain late in the week, but most of the activity
appears to be focused just beyond the scope of this forecast period.

&&

.AVIATION...
ISSUED AT 1138 PM CST THU DEC 12 2013

Clear skies overnight will give way to increasing high clouds
between 14z and 20z. Approaching weather system will spread
light rain/snow chances across TAF sites from west to east after
22z. MVFR conditions likely developing after 00z with increasing
precipitation. Calm/light south winds overnight will increase to
5-10 kts after 13z, shifting to southeast after 22z.


&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY from 3 PM this afternoon to Noon CST
     Saturday FOR ILZ075>078-080>089.

MO...WINTER WEATHER ADVISORY from Noon today to Noon CST Saturday FOR
     MOZ076-086-087-100-107>109.

IN...WINTER WEATHER ADVISORY from 3 PM this afternoon to Noon CST
     Saturday FOR INZ081-082-085>088.

KY...NONE.
&&

$$

SHORT TERM...DRS
LONG TERM...RP
AVIATION...RST