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Area forecast discussion 
National Weather Service Jackson Kentucky
400 am EDT Tuesday Jul 28 2015

Short term...(today through wednesday)
issued at 400 am EDT Tuesday Jul 28 2015

The period will be dominated by an atmosphere with only very weak
features and light flow aloft in our region...with an upper level
high centered to our SW. Conditions will be very similar to
yesterday...except for a slightly warmer atmospheric column. Will
expected scattered convection to redevelop after heating both
today and Wednesday. It should gradually die this evening with
loss of heating. With light flow and slow movement of
thunderstorms...isolated heavy rainfall may ocurr.

Long term...(wednesday night through monday)
issued at 320 am EDT Tuesday Jul 28 2015

While broad ridging will be in place across much of the southern
Continental U.S....including the Ohio River valley region...to start the
period...a fast moving upper level low will be traversing from west
to east across southern Canada. This low will have made it to
central Ontario by 0z Thursday...and will then change course towards
the NE. As it continues on this track...upper level heights will
begin falling across our region as the ridge gets pushed farther
back and east. The low will then become stalled over Hudson
Bay...keeping the broad trough in place across much of the eastern
and Midwest Continental U.S....while continuing to push the ridge farther
westward towards the 4 corner states by Friday afternoon. Expect
this troughing pattern to continue through the weekend and even into
next week...with heights oscillating from higher to lower as the low
rotates back and forth around the Hudson Bay area.

As it relates to our County Warning Area...this lowering of heights and incoming
trough will translate to northwest flow aloft through much of the period.
Multiple shortwaves are expected to traverse the
trough...however...high pressure at the surface may be enough to
Ward off any precipitation chances as these waves/boundaries near the
region.

The main concern for showers and thunderstorms will come at the
start of the period...as the closed low moves across
Ontario...pulling a strong surface low pressure system with it. A
cold front will extend southward from the surface low...across
much of the Mississippi River valley at 0z Thursday. It will
quickly swipe eastward and across Kentucky through the overnight hours
Wednesday night and into the day Thursday. Instability parameters
Wednesday night are lacking...with very little cape and a strong
surface inversion...so not expecting more than a few rumbles of
thunder through 12z. Between 12 and 18z...instability improves
with daytime heating...however the surface inversion will lift to
the middle levels. Storms would need to overcome this inversion to
produce any strong to severe activity. And given the very fast
nature of this frontal boundary...Don/T expect training or
lingering of heavy raining storms to be of much concern.

Models start to lose continuity on surface solutions after this
initial frontal boundary moves through Friday and Onward...though
they still maintain agreement in the upper levels. Another shortwave
and frontal boundary is expected to move through sometime during the
day Saturday. However...with drier northwest flow in place in the upper
levels...and high pressure over the region in the lower levels...the
European model (ecmwf) keeps out any moisture chances with the frontal zone
weakening before making it into the Ohio River valley...while the
GFS shows the precipitation weakening but still maintains some slight
chances across our County Warning Area. A similar scenario plays out for another
shortwave expected to move through sometime Sunday night into
Monday. The question will be if surface high pressure will be
strong enough to keep these boundaries from affecting eastern Kentucky.
As it stands now...model blends actually come up with generally
sub slight chances during both of these systems...so decided to
continue to exclude mention of any precipitation chances for the
remainder of the extended.

After the initial cold front Tuesday morning...northwest flow will bring in
slightly cooler temperatures. However...strong surface high pressure
in place and clear skies will promote maximum daytime radiation...so
the temperature drop will not be that great...only a few degrees from the
day before. Perhaps more noticeable than the slight change in
temperatures will be the decrease in humidity...as light winds at
the surface and northwest flow aloft will promote lower relative humidity values. As high
pressure remains in place through much of the extended...expect
temperatures to gradually warm each day...staying in the middle and upper 80s
through the weekend and into next week. Meanwhile...maximum
radiational cooling during the overnight will keep overnight lows in
the low to middle 60s through the weekend.

&&

Aviation...(for the 06z tafs through 06z Tuesday night)
issued at 307 am EDT Tuesday Jul 28 2015

Conditions were largely MVFR at the start of the period...with
some IFR and VFR present as well. An overall deterioration is
expected overnight...with mainly IFR expected by dawn. Improvement
to VFR is expected early on Tuesday morning after sunrise.
Scattered showers and thunderstorms are expected to develop on
Tuesday afternoon...bringing localized sub-VFR conditions. They
should diminish by sunset.



&&

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

$$

Short term...hal
long term...jmw
aviation...hal

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