Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 150045
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
645 PM CST Thu Dec 14 2017

.UPDATE...
Issued at 644 PM CST Thu Dec 14 2017

Updated aviation section for 00z TAF package.

&&

.SHORT TERM...(Tonight through Saturday night)
Issued at 239 PM CST Thu Dec 14 2017

Surface high pressure will keep the region relatively calm and
cool tonight and Friday, as a weak upper-level trough moves east
through the region. The low clouds are still expected to hang
around for most of the night before clearing overnight. There will
be some higher clouds associated with the upper trough over the
region when the low clouds dissipate, but they too should clear
early Friday morning. Plenty of sunshine, west winds and a dry
airmass expected Friday should allow for nearly 10 degrees of
warming compared to today.

Ridging aloft will build over the region Saturday. Southerly winds
will develop late Friday night and increase and become gusty
Saturday. The warming trend will definitely continue into Saturday
with most locations climbing well into the 50s or several degrees
above normal. Tried to lean toward the warm side of guidance both
days.

An upper-level trough will eject out of northern Mexico Saturday
night, as more substantial energy drops into its place. This will
result in the system dampening as it rides up the west side of the
upper ridge. This system will tap some moisture, but how much
forcing is left as it reaches our area will determine how much
rain we will get.

There will be a ton of dry air to overcome, but most of the 12Z
guidance does bring some modest rainfall at least into southeast
Missouri by 12Z Sunday. The NAM is the slowest and keeps the
entire area dry, while the GFS is the most aggressive and brings
the rain through the Purchase Area and the southern tip of
Illinois. The 12Z ECMWF is in the middle ground spreading the
rains through much of southeast Missouri. NAM and GFS soundings
agree that the freezing line will be near 700mb with plenty of
warm air to keep the precipitation all rain. There will be no
instability to work with, so this should be a stratiform rain
event.

.LONG TERM...(Sunday through Thursday)
Issued at 239 PM CST Thu Dec 14 2017

Fairly high confidence in the storm system bringing rain and warmer
temperatures this weekend.

The models have been locked onto this system for numerous cycles.
There are some minor strength differences among the deterministic
models but too small to be of concern. This system is generally a
weak perturbation in the southwest flow with a warm front as a
surface reflection. With temperatures expected to be in the 40s and
50s with this system...all liquid is expected. Also with little to
no CAPE combined with positive LI`s and K index values less than
30...we do not anticipate thunder at this time. I do think we will
be able to narrow the longevity of the pops with this system as it
nears. The models start to diverge with what I would call the main
trough lifting out of the southwest and through the region early
next week. Currently the blend lingers a pop into early next week.
Although confidence is not very high with this scenario...will
embrace the light pops of the blend at this time. For the most part
temperatures will be above normal through the extended. The models
are trying to bring in yet another system for the end of the
week...but its mostly outside the valid time of the current
forecast. Will monitor closely to see how this evolves with future
runs.

&&

.AVIATION...
Issued at 644 PM CST Thu Dec 14 2017

Low VFR ceilings expected at all TAF sites through the evening,
with gradual clearing overnight. North to northwest winds around 5
kts will become light west late tonight, then increase to 6 to 11
kts after 14z. No vsby restrictions expected.

&&

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

$$

SHORT TERM...DRS
LONG TERM...KH
AVIATION...RST



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