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Area forecast discussion...updated 
National Weather Service Jackson Kentucky
755 PM EDT Friday Apr 24 2015

Update...
issued at 745 PM EDT Friday Apr 24 2015

23z surface analysis shows high pressure clinging on in the far east
in the face of an approaching area of low pressure...poised to
bring severe weather to Kentucky later on Saturday...from the west. This
western low/S warm front will swing toward the area by dawn...
affecting the far southwest initially then lifting deeper into
east Kentucky through midday Saturday. The precipitation will have a tough
time reaching the ground across the area through the bulk of the
night as the very dry lower atmosphere only slowly saturates...
despite the hrrr/nam12 indications. In this environment...expect
the eastern valleys to drop off quickly following sunset...even
with the thin high clouds now in place overhead. Elsewhere...
temperatures will stay up through the night...much warmer than
last night. Have updated the forecast to nudge temperatures in the
eastern valleys down a bit...but expect them to mix out by dawn as
the air saturates and showers push over this part of the state. In
addition to the severe threat for Saturday...the latest model runs
continue to indicate that there is also a potential for excessive
rainfall depending on the tracks of the individual cells and/or an
mesoscale convective system tracking across the County Warning Area in the afternoon/evening that
certainly looks possible. These updated grids have been sent to
the ndfd and web servers.

&&

Short term...(this evening through Saturday night)
issued at 350 PM EDT Friday Apr 24 2015

Current conditions across the area feature surface high pressure
slowly sliding off to the east today. Middle and upper level cloud
cover at this time is beginning to stream into eastern Kentucky
this evening. This is ahead of a developing low pressure system
out west over the Central Plains. Cloud cover over the area will
likely keep temperatures overnight nearly uniform with southerly
warm air moving into the area through the night. At this time
overnight...the surface low slides east as a warm front develops
in the lower MS valley and moving northeast. This will bring
showers into eastern Kentucky by midnight or shortly afterward.

Heading into the predawn hours Saturday morning...the main surface
low begins to move into the middle MS River Valley and into the
Midwest with some instability beginning to enter the southwestern
counties and this may lead to a few early non severe storms and
may need to add thunder to the tonight period of the severe weather potential statement. Heading
into the day on Saturday...after earlier rainfall has moved
through...some clearing skies and recovering energy and
destabilization will then occur with most unstable cape around
1000 to 1500 j/kg over southeastern Kentucky by the 18z time
frame. This also with some 60 knot surface to 6km bulk shear will be
enough for some rotating storms tomorrow afternoon. Due to this
threat Storm Prediction Center has put the southern area in an enhanced threat of
severe weather and have put this threat in the severe weather potential statement and may need an
Special Weather Statement to highlight the threat in detail. The only threat that is a
bit questionable tomorrow will be the flash flood threat. Though
the last heavy rainfall was long enough ago that most places have
been allowed to drain and dry out. As well...green has gone into
full swing across the area alleviating the runoff potential.
However...the discrete super cell potential will add to the threat
of flash flooding as well as if an mesoscale convective system develops by late in the
evening on Saturday. May need to evaluate this during the next
model run.

Heading into Saturday evening...the warm front moves through to
the northeast and then the surface low tracks right across eastern
Kentucky with another strong shot of rainfall which may be enough
to initiate the flash flood threat. Have adjusted the quantitative precipitation forecast for the
00z to 06z Sunday night period for this rainfall. Rainfall amounts
will be lessening by 06z to 12z range Sunday night as the event
will be winding down. For now...will highlight the severe and
flood threat in the severe weather potential statement and may need an Special Weather Statement to further highlight
this. The zone forecast product will have severe potential and heavy rainfall
mentioned as well.

Long term...(sunday through friday)
issued at 350 PM EDT Friday Apr 24 2015

Any remaining rainfall should be winding down by Sunday morning as
the surface low and trailing cold front push east of Kentucky. Behind this...
skies will gradually clear as dry air filters into the region Sunday
evening...allowing for eastern Kentucky to receive a break from the
wet weather to start the work week. This is due to an area of high
pressure forecast to move slowly across the Ohio and Tennessee valleys Monday
and Tuesday.

A large cutoff low will then gradually move eastward from Texas across the
southeastern US Wednesday through Thursday. As the low moves eastward its
energy is forecasted to get wrapped into a deepening northern stream
trough. The models have come into better agreement in the past
couple of runs with the evolution of this system...where the European model (ecmwf)
solution has the area of low pressure moving along a track similar
to that of the GFS. However...the European model (ecmwf) solution keeps the low cut
off and separate from the northern stream trough...creating quite a
bit more precipitation than the GFS across eastern Kentucky through the end
of the work week. With uncertainty still existing in this part of
the extended...decided to keep precipitation in during the Wednesday/Thursday time
frame...and stuck close to the CR superblend.

Temperatures will generally be below normal and stay in the 60s for
highs and in the 40s for lows throughout the extended. During the
drier periods...temperatures will be closer to normal values.

&&

Aviation...(for the 00z tafs through 00z Saturday evening)
issued at 755 PM EDT Friday Apr 24 2015

VFR conditions will continue to be the rule through early Saturday
morning. Rain will move in from the southwest overnight and
ceilings will lower to MVFR toward dawn. Although a storm or two will
be possible with the initial arrival and progress of the warm
front...the better threat will be in the afternoon. During this
time...thunderstorms are expected to develop...some of which may
become severe. With these storms...conditions can be temporarily
reduced to near alternate mins or below depending on the strength
of the storm. For this...went with thunderstorms in the vicinity between 15 and 00z with
later updates better able to refine timing of the worst
conditions. Gusty winds are also expected with any thunderstorm
activity. Otherwise...winds will be light and variable through
most of the period before switching to the south southeast and
picking up to between 5 and 10 kts during the afternoon on
Saturday.

&&

Jkl watches/warnings/advisories...
none.
&&

$$

Update...greif
short term...shallenberger
long term...jvm
aviation...greif

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