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Area forecast discussion 
National Weather Service Jackson Kentucky
757 am EDT Sat Aug 23 2014

issued at 716 am EDT Sat Aug 23 2014

Lingering moisture from last night/S rainfall has caused areas of fog
across portions of eastern Kentucky. Given the amount of moisture...expect
this fog to stick around for the next couple of hours before slowly
lifting and burning off with daytime heating by middle morning. As
such...adjusted the weather grids to account for the morning fog
across the area. Also...updated the pop grids to better account for
the latest model data and thoughts for rain potential over the next
several hours...pushing back isolated probability of precipitation by 1 to 2 hours...and
keeping lower end in a couple hours longer. As it now
stands...updated forecast introduces isolated probability of precipitation this
morning...which is still an hour or two sooner than some of the
surrounding offices. While this might be too quick...the fact that
moisture is so abundant...and there are a few pop up showers already
showing up across southern half of the County Warning Area...felt more confident with
including probability of precipitation than not including them. daytime
heating ensues...expect things to begin developing by early
afternoon. Loaded in the latest observational data to make sure
temperatures...dew points...and winds were well reflected in the ongoing
near term forecast.


Short term...(today through sunday)
issued at 421 am EDT Sat Aug 23 2014

While 500mb heights continue to push a strong ridging pattern into
the lower Mississippi River valley and deep south...troughing
continues to linger along the New England Seaboard. Eastern Kentucky/S
position in the transition zone will continue to make US susceptible
to shortwave activity through the short term. At the surface...a
stationary boundary parked just north of the Ohio River yesterday
was the Focal Point for a strong pull of warm air advection and unstable moist air
from the Gulf. As temperatures rose during the afternoon...the atmosphere
became more unstable...and the front provided the lift needed to
initiate strong showers and thunderstorms capable of producing
torrential rains. These storms then moved S and southeast into eastern Kentucky
throughout the evening and overnight...causing flash flooding across
many locations.

For today...this frontal boundary will shift only
slightly...becoming more north/S oriented along the eastern Kentucky border
according to the latest GFS analysis. Given the similar set up to
yesterday...expect a near repeat of events...with the best
convection expected more over the western and southwestern portions of the County Warning Area.
This will not limit other scattered convection from developing
elsewhere across the County Warning Area as well. Precipitable water values are still around/above
2 inches during the afternoon and evening...with storm motion and
0-6km winds generally 10-12 knots or less. Slow moving heavy rainers
will be the story once more. While thunderstorms are definitely
possible...generally NE flow and some middle level capping may be
enough to keep severe potential at Bay for the most part. Biggest
concern will obviously be the flash flooding potential...especially
given the ongoing saturated/above saturated conditions across
eastern Kentucky.

By this evening/overnight...the frontal boundary will make a quick
push SW across the County Warning Area. This...and loss of diurnal heating and
instability will quickly reduce probability of precipitation across the region...though
latest nam12 soundings are still showing precipitable water values between 1.75
and 2.0 in. Overnight Saturday night as well. In other
words...expect coverage and thunder potential to lesson
substantially...though any storms that do persist will continue to
put down heavy rain while experiencing a slowing storm motion. Flash
flooding threats...therefore...will continue into the overnight

The frontal boundary will shift off to our SW for the forecast
Sunday...with the upper level ridge encompassing much of the Ohio
River valley. Diurnal driven instability will a weak
surface disturbance sets up across the south central portion of the
state. This will be the primary epicenter for storm
development...however anything strong is highly unlikely given the
unsupported weak wind profile. Precipitable water values will show a lessening
trend...but are still sticking around the 1.75 in. Range with little
to no storm motion. Wouldn/T be surprised to see some more good
heavy soakers this day as well. Chances for showers will quickly
drop off with loss of daytime heating in the evening.

Given the continued building heights across the region...and a more
tropical airmass moving into the Ohio River valley...temperatures will
continue to climb to just below the 90 degree mark today and
tomorrow...with high humidity values making it feel closer to 100
degrees. Clouds and the potential for showers will keep temperatures from
reaching even higher. Min temperatures will remain well above normal under
this warm airmass...only dipping down into a humid upper 60s and low

Long term...(sunday night through friday)
issued at 458 am EDT Sat Aug 23 2014

By Sunday night...the upper level and surface high will be well in
place through the end of the period. With this type of
pattern...the days will be fairly warm and moist and there will
pretty much be a slight chance to a chance for thunderstorms every
afternoon and evening. With the high pressure in place...the air will
only be moist in the lower layers. This will allow for a Little Break
from the flash flooding threat that has been so prevalent during this
very moist August. So far this August...Jackson has received 6.28
inches of rain...with 3.69 inches being the normal rainfall for
August. For temperatures...went with the model blend and then nudged
them toward the 00 gmt raw European model (ecmwf).


Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 756 am EDT Sat Aug 23 2014

Lots of vlifr conditions around eastern Kentucky this
morning...especially near areas that received heavy rain yesterday
afternoon and evening. Expecting the fog to start lifting between 12z
and then returning to VFR by 14 -15z. Expecting isolated to scattered
thunderstorms again this afternoon starting between 18 to 21z.
Fog and mist will be forming again tonight...especially in valleys
and locations that receive heavy rain today.


Jkl watches/warnings/advisories...


short term...jmw
long term...jj

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