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Area forecast discussion 
National Weather Service Jackson Kentucky
955 am EDT Friday Aug 1 2014

issued at 955 am EDT Friday Aug 1 2014

Updated the zone forecast text product to remove mention of fog not
that all the fog has burned off around the area. Left in mention of
late morning through early evening shower and storm chances as the
latest data from the sref and hrrr both still supporting it. Will
monitor that part of the forecast over the next few hours to
determine if another update will be needed.


Short term...(today through saturday)
issued at 326 am EDT Friday Aug 1 2014

The models start out in good agreement with an upper low near hudsons
Bay. The key feature is a short wave moving down the back side of the
upper trough. This short wave is forecast to intensify as it dips
south into the central US. By tonight...the short wave will extend
from Lake Superior south across central Illinois into Louisiana. With
this synoptic pattern...the cold front is well the south of the area
along the Gulf Coast and the blocking ridge out west is blocking any
fronts from moving into the area. The short wave trough axis is forecast
to move across eastern Kentucky on Saturday evening. The models are
in good agreement with the timing of the trough passage. The main
driver of the weather will be the general instability associated with
the upper low and then the passing of the upper trough axis. There
has been some middle level capping that has held down any clouds from
growing big enough to produce rain showers. As the trough nears...the
middle level capping will begin to erode and the net result is that some
isolated to scattered thunderstorms and showers will be able to form.
There are enough differences in how the models handle this
system...that confidence is lower than normal with how widespread
the precipitation will be. There could be a scenario where the energy
will pass to the north and south of the area and there will be
minimal convection of eastern Kentucky. The probability of
precipitation is a bit lower than what the previous forecasts had.

For temperatures used a blend of the NAM and GFS MOS and then made
some adjustments for terrain effects.

Long term...(saturday night through thursday)
issued at 300 am EDT Friday Aug 1 2014

The persistent trough over the eastern U.S. Will deamplify a bit
through the long term period but remain pretty much in place in the
means. A passing shortwave will keep the threat of showers/storms in
our forecast for Saturday night and Sunday. Weak high pressure will
then build into the region by early next week and most locations
should be dry as a result with the exception of along the Virginia
border where proximity to deeper moisture just to our southeast may
allow a few showers/storms to fire with daytime heating Monday
afternoon. A cold front will sag southward slowly through time into
the Ohio Valley. Most models keep this front well to our north
through midweek...but the 01/00z European model (ecmwf) shifted course and is an
outlier dropping it all the way through our area. Will continue with
a dry forecast for now through Wednesday before rain chances
increase again on Thursday as the front approaches. Temperatures
will moderate slowly through time but only up to normal levels for
early August by Wednesday and Thursday.


Aviation...(for the 12z tafs through 12z Saturday morning)
issued at 800 am EDT Friday Aug 1 2014

Expecting VFR conditions through the near dawn tomorrow at the taf
stations...however there will be some vlifr in some of the
valleys...especially near rivers and streams. The fog should be
burning off by 13z. The might be some tempo IFR as the fog lifts out
of the valleys...some of the stratus may move across the airfield. Looking
for some isolated to scattered showers and thunderstorms moving
across the area from the middle morning through around 6z. The timing is
too uncertain to put in any tempo groups at this time...however do
expect some MVFR conditions under the storms if they move across a taf
station. Fog is more likely tomorrow due to the rain which is
expected today.


Jkl watches/warnings/advisories...


short term...jj
long term...Abe

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