Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 090518
AFDPAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
1218 AM CDT Wed Jul 9 2014

.Update...
Issued at 1218 AM CDT WED JUL 9 2014

Revised aviation discussion for 06Z TAFs.

Update...
Issued at 543 PM CDT TUE JUL 8 2014

Convection finally seen developing from near KEVV to KHSB to KCGI
along ill-defined boundary, and supported by weak diff PVA h7/h5
dropping SE across the area. ML capes only 1000-1500 on avg with
lapse rates around 6. Thinking the chance of severe is remote at
this point. Probably not slight risk worthy. Of course, one never
knows and a pulse storm still cannot be ruled out. Plan on down
playing severe chances even more in the HWO, and will modify PoPs
slightly based on latest high resolution model output. Some of the
meso models point to areas from SE IL into the Pennyrile region of
west KY, as the zone where better instability will progress with
time. As we speak, greatest instability is in an axis from SEMO to
the confluence of the Wabash and Ohio.

&&

.Short Term...(Tonight through Thursday night)
Issued at 117 PM CDT TUE JUL 8 2014

Not sure about this afternoon. It is under-played, attm, with a
dearth of radar returns. Still, Laps shows surface destabilization
occurring with negative LI`s, and dew points near 70F, and primary
cold front still to our north, dropping in. Upper circulation
center noted on WV imagery rotating across Great Lakes should
drive front on thru FA this pm/early evening. Would anticipate
with further juicing of the atmos this pm, convection should fire
along/ahead of said frontal boundary. That means a higher chance
south, vs north, but we`ve cut back strictly into the chc cat for
now. Also NAM races it on thru, GFS hangs it a little but races it
thru compared to previous runs, so we think the chance (including
SPC swody1 SLGT risk) will be mainly thru the pm/early evening
hours with notable cut-off after midnight with fropa.

After that, a nice cooling in both surface air and dew point temps
should make the mid to close of the week pleasantly mild.

.Long Term...(Friday through Tuesday)
Issued at 300 PM CDT TUE JUL 8 2014

An unusually active pattern for mid summer will continue through the
long term. The general theme will continue to be troughing over the
East and high amplitude ridging over the West. Variations in the
amplitude of the mid level flow will continue to dictate our weather.

As far as the daily details...surface high pressure will weaken and
move off the East Coast on Friday. A light southerly return flow
will bring somewhat warmer and more humid air northward.

The low level flow will increase from the southwest over the
weekend...bringing some of the highest 850 mb temps so far this
season. Most of the recent gfs/ecmwf runs have indicated a nose of
850 mb temps in the lower to mid 20s over our region by Sunday. This
would support highs in the lower to mid 90s. However...the forecast
is not straightforward due to the risk of mesoscale convective
systems muddying the waters...similar to what occurred here over the
past 24 hours.

Friday night through Sunday night...mid level ridging over the
southern Plains will strengthen and expand northeast into the Lower
Ohio Valley. A pool of moist and very unstable air will become
established over much of the mid section of the country. Convective
complexes will likely develop over the central Plains or Missouri
Valley...in the vicinity of a frontal boundary. Weak northwest mid
level flow will tend to steer these complexes in our direction. Will
continue low pops in the forecast for the entire weekend to account
for the possibility of decaying convective systems reaching our
area. Pops will be slightly higher north and east of a kmdh/khop
line...where capping will be weaker and steering flow will be
stronger on the periphery of the high.

Early next week...an unseasonably strong cyclonic vortex will drop
south into the Great Lakes region. This will push a cold front
southward across our region...most likely on Monday. The ecmwf has
been more aggressive with its southward push of Canadian air. In any
case...Tuesday will see the start of a potentially significant
cooldown. Will keep a slight chance pop in the forecast for Tuesday
as impulses will likely be rotating southeast around the Great Lakes
vortex.

&&

.Aviation...
Issued at 1218 AM CDT WED JUL 9 2014

A weak cold front will continue to sag slowly southward across the
region overnight. Winds will shift to the west and eventually
northwest in the wake of the frontal passage. VFR conditions will
prevail through the planning period. Some patchy fog may form
towards daybreak, but drying aloft should preclude widespread
development.

&&

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

$$





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