Area Forecast Discussion
Issued by NWS Paducah, KY

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943
FXUS63 KPAH 102318
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
518 PM CST Sat Dec 10 2016

.UPDATE...
Issued at 518 PM CST Sat Dec 10 2016

Aviation update.

&&

.SHORT TERM...(Tonight through Monday night)
Issued at 125 PM CST Sat Dec 10 2016

The modeling of the short term forecast is increasingly coming in
line with time. The broad surface high pressure system centered
over the Commonwealth drifts east to mid Appalachia tonight,
allowing a nice southerly return fetch of air. Coincident with
that, low level wind fields off the surface increase to 40 to 50
kts thru tmrw, enabling a transport of cloud/moisture and warmth
into the still very dry low layers at this writing. This will all
set the stage for our rain event tmrw.

Overnight...anticipate an early low temp with near steady or even
slight rise in mercury as the lower trop warm advection kicks in
more earnestly with time. It takes awhile for the column to
saturate thru the 20+ F dew point depressions in the lower trop,
so not much if any pcpn is anticipated thru tmrw morning (will let
collab play that out on particulars).

Sunday gets wet by pm hours and the categorical rain event
continues Sun night. Upper dynamical energy will organize and
propel a cold front from west to east across the FA during the
overnight hours. And while yesterday`s Day 3 convective outlook
annotated areas from LIT to LMK to ILN with thunder, today`s
outlook for same time range (tmrw-tmrw night) are more reserved,
and confines its chances just to our south. This is in line with
even the most aggressive NAM, which keeps all marginal instability
parameters played out just to our south. Still, with high PW`s and
a saturating column, and good dynamical/synoptic lifting
mechanisms moving through, a welcomed rain event producing 1/4"
north/west to 3/4" south/east is anticipated. And like our
inherited forecast, we`ll linger the end pop thru Monday morning,
til the slowing front makes final passage/clear out Monday pm.

.LONG TERM...(Tuesday through Saturday)
Issued at 125 PM CST Sat Dec 10 2016

The long term portion of the forecast starts off with higher than
average confidence and good overall model agreement. However,
confidence drops to below average beyond Wednesday with much greater
variability in forecast model solutions. The main concerns during
this time frame include the cold weather and chance for potential
wintry precipitation Friday into Saturday.

Starting with Tuesday, a cold front is progged to make passage
during the day. No precipitation is expected given the dry
atmospheric profile. In the wake of the front, cold Arctic high
pressure will build into the region through mid week. The result
will be unseasonably cold temperatures both Wednesday and Thursday.
for that matter, highs on Wednesday are only forecast in the upper
20s to mid 30s, dropping into the mid and upper 20s on Thursday.

Low pressure is forecast to develop in the lee of the Rockies on
Friday and move east towards the Mid Mississippi Valley by Saturday.
A saturating atmospheric profile ahead of the low will result in
increasing chances for precipitation, particularly from late Friday
into Saturday.

Models are rather inconsistent on precipitation type during this
time. The consensus starts off precipitation as snow or a wintry
mix, with a transition over to rain by Saturday as the thermal
profile gradually warms. To keep things simple, the forecast
currently includes only rain or snow. However, it would not be
surprising to see the eventual addition of sleet and freezing rain
if current model trends remain in tact. There are too many variables
at this point to forecast with much confidence. Nevertheless, the
time period from Friday into early Saturday will need to be closely
monitored for potential weather impacts in the coming days.

&&

.AVIATION...
Issued at 518 PM CST Sat Dec 10 2016

Band of clouds with bases 4-6k/ft forecast to move across the area
overnight. Some breaks possible. Cigs will lower from 18z-00z
Sunday ahead of an approaching cold front, into the MVFR category
most areas by 00z. Light rains should develop from 18z on. For
now, no vsby restrictions given low confidence. Light southeast
winds tonight will become southerly and increase to sustained
10-14kts midday Sunday on into the afternoon.

&&

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

$$



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