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Area forecast discussion 
National Weather Service Jackson Kentucky
1032 PM EDT Thursday Aug 21 2014

issued at 1031 PM EDT Thursday Aug 21 2014

A new forecast update was just sent out addressing the possibility of
thunderstorms moving further south into our forecast area later
tonight than previously thought. Based on current satellite and radar appears that the northern 2 or 3 tiers of counties of
our forecast area could experience isolated to scattered showers and
thunderstorms associated with a large thunderstorm complex that is
currently moving across parts of central Indiana and west central
Ohio. The sky cover...precipitation type...and
precipitation amount forecast grids were all updated to reflect
current trends and the latest hrrr forecast data. The hazardous
weather outlook was also updated to reflect the new thunderstorm
probabilities and the further southward movement of the storms

Update issued at 758 PM EDT Thursday Aug 21 2014

Some significant updates were made to the forecast grids for the rest
of the tonight into early tomorrow morning. Will be issuing a new
zone forecast product with the prefirst period from day shift
removed. The grids and the text forecast product have both been
updated to reflect the fact that all precipitation has now moved out
of eastern Kentucky. The latest nam12 and hrrr models both are
keeping precipitation out of the area until 8 or 9z tonight. Based on
this...and the latest radar imagery...which has a large thunderstorm
complex moving across northern appears that the model
data is on track and that the storms currently moving across Indiana
will stay mostly north of the area as they move across southern Ohio
late tonight and early tomorrow. We may see a few showers and storms
fire up along thunderstorm outflows in our northernmost counties
along and north of I-64 around 8z tonight. The sky cover grids and
forecast were also updated to reflect current trends of partly to
mostly cloudy skies across the forecast area. Considering the amount
of rain eastern Kentucky has received the past several days...and
with clouds breaking up a bit tonight...we should still see areas of
fog in our valleys. Locations that received rainfall
today...including Ridgetop locations such as the Jackson weather
office...could also see some MVFR fog overnight. The hazardous
weather outlook will also be updated shortly to reflect the lack of
thunder through dawn tomorrow. A new set of zones will also be issued


Short term...(this evening through Friday night)
issued at 355 PM EDT Thursday Aug 21 2014

19z surface analysis shows a seasonally strong area of low pressure over
the High Plains with high pressure over the deep south. This nearby
high is not enough to prevent the latest incarnation of mesoscale convective system activity
from diving through eastern Kentucky. This is taking advantage of
high instability throughout the area given temperatures in the upper
80s and dewpoints in the lower 70s. In addition to the severe
thunderstorm threat...high precipitable waters ...low ffg...and a potential for
training will keep flash flooding a concern through the evening.

The models are in good agreement aloft through the short term portion
of the forecast with a large area of ridging stretching from the
lower Mississippi Valley into the Tennessee Valley. As it does so...a
deep low to the northeast will send packets of energy through the
Ohio Valley and into the central Appalachians in fairly fast
northwest flow. This will place at least northeast parts of the jkl
County Warning Area in the storm track and as prime real estate for mesoscale convective system activity.
Given the model agreement have favored a blend with extra emphasis on
the hrrr and nam12 for the first 12 to 24 hours.

Sensible weather will feature on going thunderstorm activity
diminishing into the evening...but progressing south with the favored
instability. Later tonight...partly clouds skies and the moisture
from the rain of this afternoon and evening will likely lead to
areas of fog...locally dense. Indications are that the next round of
storms stay to the northeast of the County Warning Area tonight. After the fog Burns
off on Friday morning the instability will build again with another
very humid and warm day. This will be a similar setup for severe and
excessive rain potential...mainly in the northeast based on the
expectation of early storms tracking just outside of the County Warning Area and
development on their southwest flanks. Likewise...patchy fog will be
an issue for the area later Friday night given a similar setup...
but still dependent on the rains early in the day and evening.

Used the consshort as a starting point for the T...TD...and winds
through the first 24 hours and the superblend thereafter. Made some
minor adjustments based on terrain for lows tonight and Friday night.
As for probability of precipitation...ended up higher than guidance...except for the met
north of jkl on Friday night...through Saturday morning owing to the
tendency for storms to expand southwest of their depictions in the

Long term...(saturday through thursday)
issued at 315 PM EDT Thursday Aug 21 2014

Strong ridging will likely hold over the area for the balance of the
extended part of the forecast. Shower and thunderstorm chances will
continue each day through the middle of next week. In
addition...warm and muggy conditions will remain anchored beneath
the ridge. Best time for showers and storms will continue to be each
afternoon/evening...but cannot rule out an isolated shower or storm
at any time into next week. GFS MOS is likely a bit too high and
will continue to go between GFS and met MOS through Saturday. European model (ecmwf)
seems to be a good compromise with regards to temperatures.


Aviation...(for the 00z tafs through 00z Friday evening)
issued at 758 PM EDT Thursday Aug 21 2014

This evenings tafs will feature a mostly precipitation free overnight
period...with partly to mostly cloudy skies...light winds...and fog.
Sjs could see some isolated showers and storms nearby from around 8z
through 15 or 16z. Jkl could begin to see showers and storms in the
area from 16z Onward. Loz and sme should see only isolated showers
and storms from 16z Onward. Expecting VFR conditions to prevail at
the taf sites through around 6z tonight. After that the tafs will
feature MVFR fog with scattered to broken middle and high level cloud cover
through 12 or 13z. The fog should be gone by around 9am on Friday.


Jkl watches/warnings/advisories...


short term...greif
long term...kas

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