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Area forecast discussion
National Weather Service Jackson Kentucky
412 PM EDT Wed Aug 21 2019

Short term...(this evening through Thursday night)
issued at 343 PM EDT Wednesday Aug 21 2019

Diurnally driven cumulus has started to develop over the last hour or
two, in addition to some high clouds moving over the region. An
upper level shortwave has just shifted east of the region, so expect
better convective development to be outside of our County Warning Area. However,
can't rule out an isolated shower or thunderstorm popping up this
afternoon, especially with cape values over 3,000 j/kg in most
locations. Furthermore, like yesterday, any storm that does develop
could be strong as a result, and may produce strong winds given the
dcapes over 1,000 j/kg yet again today. So far, however, the cams
are holding strong that convection should not develop until later in
the we shall see if that holds true. Only included low
end isolated pops at this time.

As we head into the evening and overnight, ample instability will
remain in place. This will couple with lowering heights aloft, and a
cold front which is poised to move southeast closer to the Ohio River
through the overnight. Cams are in fairly good agreement that after
some isolated convection potential during the evening, a larger
complex of showers/storms will develop and move eastward into the
County Warning Area for the second half of the overnight. The hrrr is the only cam
not showing this, or at least at the timing of the others, but it is
also at the very end of its run, so taking that into consideration.
The GFS and European model (ecmwf) are also on board with precip after 6z as well.

Pops will continue to increase throughout the day Thursday as moist
SW flow increases and the front begins to traverse southward into
the state. The introduction of overcast cloud cover and precip will
prevent temperatures from being as hot as previous days, with highs
in the mid and upper 80s. However, cape values of between 2,000 j/kg
and 3,000 j/kg will still lead to decent convection ahead of and
along the frontal boundary. This boundary is then expected to become
stalled across the state heading into the overnight Thursday night,
with the much of the County Warning Area still expected to see scattered to numerous
showers and thunderstorms. Storm Prediction Center has US in a marginal severe risk for
the Thursday/Thursday night time period. Hopefully this system will
finally bring US a more widespread soaking rain as well, with precipitable waters
topping well over 2 inches in some locations after 6z Friday. Wpc
has placed US in a marginal risk of excessive rainfall for this time
period as well.

Long term...(friday through wednesday)
issued at 412 PM EDT Wednesday Aug 21 2019

The models are in decent agreement showing a northern stream
trough over the northeastern Continental U.S. And zonal flow over Kentucky
for the start of the long term. Meanwhile, ridging will be the
story for north-central Continental U.S. For the end of the work week. This
pattern will gradually shift east, with ridging taking hold over
the northeast for late weekend. Another northern stream trough
will then build and begin advancing towards the Great Lakes and
Ohio Valley by Tuesday. A stalled surface front will move slowly
over eastern Kentucky into early Friday morning, but eventually
will make its way southward over the Tennessee Valley Saturday
morning. High pressure will build over the Great Lakes during this
time as well. This high pressure will then progress eastward
through the weekend, with a cold front slated to approach and
stall over the upper Mississippi Valley Tuesday. High pressure
will also take hold to the east of Kentucky for midweek.

The best chance for showers will be Friday as the cold front
stalls over the state. Instability is not impressive, but a few
thunderstorms in the afternoon and early evening cannot be ruled
out. By the weekend, shower and storm chances will become more
diurnally driven. Both the GFS and ECMWF, as well as the Canadian
and NAM, show little to no quantitative precipitation forecast for most of eastern Kentucky for
Saturday. Some chances remain along the Tennessee and Virginia
borders, however. Furthermore, the European model (ecmwf) shows no quantitative precipitation forecast for Sunday
into Monday, whereas the GFS shows some activity in east-central
Kentucky during this time. Lowered pops given by the blended
solution for Saturday and Sunday because of this.

High temperatures will be in the lower 80s through the weekend,
but rebound back to the mid 80s by next Tuesday. Lows will
generally be in the lower to mid 60s Saturday morning, but
gradually increase to be in the upper 60s by midweek.


Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 215 PM EDT Wednesday Aug 21 2019

VFR conditions are currently in place and should remain through
the taf period. Diurnally driven cumulus are starting to pop up across
eastern KY, and may become more scattered as we head into the
afternoon. Can't rule out a isolated shower or thunderstorm
developing as a result, but low end chances warrant mention in
the tafs at this time. Will update if necessary. Better precip
chances will move in overnight as a cold front shifts southeast closer to
the state, heights aloft begin to lower, and stronger SW flow
takes hold. Started thunderstorms in the vicinity generally after 3z given the fairly good
hi-res model agreement, though there is still quite a bit of
uncertainty on timing and location of storms at this point.
Chances will continue through the first part of the day tomorrow,
before increasing after the taf period as the cold front begins to
shift south into the state. SW winds will be predominate through
the period, generally under 10 knots, though some gusts up to 15
knots will be possible during the afternoon today.


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