Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 161115
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
615 AM CDT Wed Aug 16 2017

.SHORT TERM...(Today through Friday night)
Issued at 309 AM CDT Wed Aug 16 2017

Looks like a wysiwyg forecast today. Random convection, mainly to
our west, driven by weak support aloft and marginal instability.
As a band of moisture lifts NE across the area today in mid trop
SW flow, will maintain very low chance / slight chance PoPs for
what should be a similar outcome. Areas will again miss out on
rain. Low chance PoPs will continue tonight, primarily over the NW
1/3 of the area ahead of an approaching frontal boundary. PoPs
should peak Thursday with fropa, then diminish rapidly from west
to east Thursday evening. Dry weather will return for Friday/Friday
night with weak high pressure returning. Heat index values may
top out in the upper 90s some areas this afternoon and Thursday
afternoon. Maybe a couple of 100 degree values. Favored a hi res
blend in the short term (GFS seems overdone). After that, used a
model consensus. MOS and persistence for temps.

.LONG TERM...(Saturday through Tuesday)
Issued at 309 AM CDT Wed Aug 16 2017

The med range models were synchronized well on a well-developed mid
level shortwave axis moving through the PAH forecast area early Sat.
Though there will be a minor surface reflection of lower surface
pressures, this feature will have limited return moisture associated
with it, so this will tend to limit the coverage of showers and
tstms. Thus, we will go with an "isolated showers and tstms"
forecast during the daylight hours, which was a slight modification
of the initialization model blend.

Broad ridging aloft will replace the lower heights on Sun. Some
model indications are that, in the unstable lower trop, isolated
updrafts may manage to sustain themselves enough for measurable pcpn
to occur in the afternoon along the MS River (mainly southeastern
MO), despite the profile being on the dry side above 850 mb. Who
knows, isolated convection might even linger into the evening, if
you buy the GFS.

On Eclipse Day, Monday, August 21, the deterministic med range
models suggest that the broad ridge over our region may be
suppressed slightly by shortwave energy moving through. The precise
timing of any ripple or ripples of energy that could drive deep
moist convection is not attainable at this point. A smoothed version
of the initialization blend yields the possibility of isolated
showers and tstms during daylight hours, mainly over the
southeastern half of the region where low level moisture should be a
bit deeper. Currently, forecast cloud cover has increased some for
Mon, and around eclipse time (18Z) we could have 30-40% coverage of
the celestial dome associated with the possible convection. This of
course is subject to change, especially if you factor in cirrus
blowoff from possible tstm complexes outside our region in MO/IL/AR.

Another mid level shortwave trof axis is progged to sweep through
our region sometime on Tue, as a low pressure system begins to
deepen across the Great Lakes. While moisture convergence does not
appear robust, there apparently will be enough positive vorticity
advection to trigger scattered showers and tstms across the entire
region. This is supported by the ensemble means.

&&

.AVIATION...
Issued at 615 AM CDT Wed Aug 16 2017

Scattered IFR/LIFR conditions extended from KHSB up to KEVV, with
MVFR conditions some areas as well. Convection will continue to
move across southern IL early this morning. Additional convection
possible through the day and into tonight elsewhere. However,
confidence in coverage and timing is too low to warrant a mention.
Winds will become SSW 5 to 10 kts, with scattered to broken
clouds both lower and upper level, category VFR.

&&

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

$$



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