Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 142022
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
322 PM CDT Fri Jul 14 2017

.SHORT TERM...(Tonight through Sunday night)
Issued at 321 PM CDT Fri Jul 14 2017

Looking into the remainder of the afternoon and into the early
evening, anticipate two primary areas of convective activity.

Firstly, the more persistent shower and thunderstorm activity will
be initially confined to western and southern sections of
Southeast Missouri. This area will be in a zone of increased
lift/shear/instability with an approaching MCV (Mesoscale
Convective Vortex) left over from an earlier MCS (Mesoscale
Convective System) over southeast Kansas, now moving into south
central Missouri at this time. Secondly, overnight convection over
southeast Missouri induced a differential heating/density boundary
which has provided a northern edge of 2400-3000 J/kg CAPE plume
from northeast Arkansas.

As this MCV works eastward this afternoon and this evening,
convection will be generated further east into southeast Missouri,
southwest/southern Illinois, and into extreme southwest Kentucky.

A secondary area of convective activity will be generated from
outflows from morning convection in Tennessee. Again, differential
heating/density changes will induce theta-e convergence zones
providing a source for convective activity, mainly over western
Kentucky.

Given the slower movement of these storms in the weakly sheared
environment ahead of the MCV, heavy rain will be the primary
concern. However, dry air intrusion along the northern edge of the
MCV, as well as the southeast Missouri/extreme Southwest Kentucky
could support enhanced downdraft CAPE and some wet microburst
potential (e.g. damaging wind gusts).

Further to the north, surface flow becomes largely divergent,
limiting any significant development of thunderstorms.

As upper level ridging builds in behind the slowly southward
moving frontal boundary, rain chances through Saturday will be
shifted to the southern border counties of southeast Missouri and
West Kentucky before ending completely late Saturday afternoon.

Issued at 321 PM CDT Fri Jul 14 2017

The medium range model solutions were in reasonable agreement
regarding the mid level pattern across the CONUS. A broad, flat
ridge initially covering more than half of the southern states is
forecast to expand eastward with time. Meanwhile, the more active
westerlies will remain to our north. Monday, a dry frontal passage
through our region from the north is expected. The GFS depicted a
possibility of a vulnerability in the capping inversion aloft on Tue
in the Pennyrile region of KY, but otherwise the blend provided a
dry forecast for our region for most of the week.

By Thursday night, shortwave energy is progged to impinge on the
ridge, bringing a surface boundary closer to the PAH forecast area.
This feature should provide a trigger for scattered shower and tstm
development in the moist and unstable atmosphere, mainly Friday.

High temps are expected to inch up through the lower half of the 90s
during the extended forecast period, with lows inching up through
the lower half of the 70s. Especially by mid week, dewpoints in the
lower 70s will be conducive to heat index readings from 100 to 105,
with higher readings possible.  We collaborated on including warmer
WPC numbers for temps.
.LONG TERM...(Monday through Friday)


&&

.AVIATION...
Issued at 1238 PM CDT Fri Jul 14 2017

Main challenge for this afternoon is the timing and coverage of
convective activity in and near the WFO PAH TAF sites. Remnant
outflow boundaries from overnight rain activity complicating
determination of mean wind direction. In the absence of distinct
rain signals, utilized vicinity showers. Kept ceilings/cloud bases
in and visibilities in VFR category.


&&

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

$$

SHORT TERM...Smith
LONG TERM...DB
AVIATION...Smith



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