Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 190000
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
600 PM CST Sat Feb 18 2017

.UPDATE...
Issued at 547 PM CST Sat Feb 18 2017

Updated aviation discussion for 00z TAFs.

&&

.SHORT TERM...(Tonight through Monday night)
Issued at 104 PM CST Sat Feb 18 2017

Upper Low now drifting across PAH FA is pinwheeling scattered
showers about the area, as seen on latest radar pics/loop. This
will continue into the evening hours, then wind down/diminish, as
the Low drifts off to the east.

Clearing is possible later tonight/tmrw, but gridded time/height
cross sections show boundary layer moisture remains high.
Therefore would anticipate low clouds and/or fog develop with any
late night clear-out, and this is reflected in the MOS guidance as
well.

Tmrw should eventually see a scour out of clouds though, with
sunshine and warmth returning as High pressure works in overhead
at the surface and aloft. Look for a rebound into the lower 70s
both Sun-Mon.

Clouds increase again late Mon-Mon night as the ridge moves east
and height falls work in from the west. That`ll also bring an
introductory chance of showers, which will include a small chance
of thunder for the SEMO Ozarks Monday evening, as suggested by
elevated instability and the latest swo.

.LONG TERM...(Tuesday through Saturday)
Issued at 201 PM CST Sat Feb 18 2017

At this time, forecast confidence is 30-50% on coverage, timing and
and intensity of precipitation events in the extended forecast
period.

Model runs up to last Wednesday were hinting at a bifurcation of the
highly meridional/narrow amplitude trough in the Central U.S. on
Monday. This trend has continued with the last two medium range
numerical model runs as well. The lower forecast confidence is due
to both the ensembles, as well as the deterministic guidance
developing and deepening a low over Texas Monday Night/Tuesday, then
pushing this closed low through the Gulf of Mexico. In these type of
scenarios, a significant amount of moisture advection/transport is
intercepted in the Gulf, leaving the WFO PAH forecast area high and
dry. For now, have used a blend of the deterministic 12z GFS and
00z/12z ECMWF for the placement and coverage of precipitation on
Tuesday and Tuesday Evening, keeping any measurable QPF
(precipitation amounts) focused along and ahead of the frontal
boundary.

The approach of a Northwest U.S. trough and the persistent Gulf of
Mexico Low will impress ridging over the WFO PAH forecast area on
Wednesday and Wednesday night, this signal is consistent among most
of the medium range guidance.

By Thursday, the increasingly baroclinic middle/upper level low in
the intermountain states in the Western U.S. generates some intense
lee side surface cyclogenesis over Kansas, creating an significant
warm air advection zone stretching almost to the east coast.
Uncertainty late Wednesday night into Thursday morning exists as to
the degree/rapidity of moisture return from the Gulf of Mexico and
the exact location and timing of a developing warm frontal zone and
the corridor of strongest isentropic lift.  Given that uncertainty,
went with a GFS/ECMWF blend into Thursday night, focusing more on
the favored zone of isentropic lift for precipitation chances.

On next Friday, both the ECMWF and GFS are progressive with the bulk
of the energy in the broad trough moving toward IA/WI. Given the
sharp baroclinic zone and warm air advection, this may be the best
chance for thunderstorm activity next week.  Cannot rule out some
significant or severe thunderstorms for next Friday, but the genesis
point still out in the North Central Pacific, it is hard to get too
excited about the coverage or intensity of severe weather at this
time. However, plan to continue emphasis on best chance of
thunderstorms on Friday, along with gusty winds.

Adjusted maximum/minimum temperature upward 1-2 degrees above

&&

.AVIATION...
Issued at 547 PM CST Sat Feb 18 2017

Current precipitation will move off to the east with the upper
level area of low pressure during the evening hours. Through the
evening hours, MVFR vsbys and cigs will prevail before lowering
during the overnight hours. Model guidance strongly suggests a
thin layer of moisture lingers until Sunday morning. Have clouds
continuing to lower along with visibility til dawn. Conditions
should become IFR between 05z and 09z. Some guidance suggests LIFR
conditions and have included that in TEMPO groups. Clouds and fog
should burn off and move out as high pressure settles over the
region on Sunday with all areas gradually becoming VFR between 14z
and 18z.


&&

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

$$

AVIATION...ML


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