Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 211339

Area Forecast Discussion
National Weather Service Jackson KY
939 AM EDT THU JUL 21 2016

Issued at 939 AM EDT THU JUL 21 2016

12z soundings and water vapor imagery indicate mid level dry air,
which will be mixing down this afternoon. In the higher terrain
KY mesonet shows dewpoints of 52 at Dorton and 59 at Black
Mountain. With drier air mixing down this afternoon we will see
dewpoints lowering and maximum afternoon temperatures higher than
yesterday. This was already depicted in the current forecast. Have
updated the NDFD based on latest observational trends, but this
resulted in very little change to the previous forecast for this

UPDATE Issued at 635 AM EDT THU JUL 21 2016

Drier air will continue to mix down across the area today keeping
skies mostly sunny and the weather dry. This will allow temps to
surpass the 90 degree mark this afternoon. That being said,
forecast remains on track so did a quick refresh to the hourly
grids. Sent updated grids to NDFD and web servers.


.SHORT TERM...(Today through Friday)
Issued at 352 AM EDT THU JUL 21 2016

High pressure will remain in control of our weather today. Drier
mid level air, currently seen on GOES WV imagery, will work its
way through most of our area, helping dew points mix down to near
60 degrees in spots. So even though temps are expected to surpass
90 degrees this afternoon, humidity will be low compared to recent
days. Additionally, MCS activity to our northwest may throw some
debris cloudiness overhead from time to time, especially in the
southwest portion of the forecast area.

The main upper level ridge will shift slightly more to our west
tonight. This will allow the low level winds to turn towards the
southwest on Friday, ushering in higher moisture. A wave in the
upper level flow is progged to drop southeast around the ridge
towards our area late Friday afternoon, bringing shower and
thunderstorm chances back into the forecast. The best chance for
shower and storm activity will likely be beyond the short term
period, into Saturday morning and afternoon.

Temperatures will reach into the lower 90s today and tomorrow.
However, heat indices are expected to reach 100 degrees in spots
on Friday afternoon due to the higher dewpoints. Additionally, debris
clouds and any shower activity late Friday adds uncertainty to
the temperature forecast.

.LONG TERM...(Friday night through Wednesday)
Issued at 352 AM EDT THU JUL 21 2016

A persistent upper level ridge over the central United States
continues to be the focus for the first portion of the long term
forecast. This ridge in conjunction with the development of surface
high pressure over the southeastern United States will allow for
decent moisture transport into the Ohio Valley, creating heat
indices that will approach the 100 degree mark over portions of
Eastern Kentucky. That being said, a few models have been hinting at
some shortwave passages throughout the weekend that may help
moderate temperatures and keep us below advisory criteria. It should
be stated that the current regime presents its own challenges in
regards to predictability, and given historical model performance in
passing these shortwaves through the periphery of a strong ridge it
was decided that PoPs should hang around the 30-40 range during peak
heating over the weekend.

Towards the start of the work week our next weather maker begins to
take shape as a trough begins to deepen over the Great Lakes and
amplify the largely zonal flow over the northern United States. As
this low pressure system propagates east it will drive a cold front
into the mid-Atlantic late Monday into Tuesday morning. Following
frontal passage we should see a brief reprieve from the oppressive
heat in days past, as we return to more reasonable summertime
conditions. As the work week progresses, conditions should remain
fairly calm save a few diurnally driven showers and thunderstorms.


.AVIATION...(For the 12Z TAFS through 12Z Friday morning)

Drier air aloft will mix down throughout the day today, allowing
for VFR conditions to prevail. There is some fog potential
tonight as winds turn to the southwest ushering in more moisture.
However, do not think that moisture will recover quick enough to
produce anything more than some light fog in the river valleys.
Winds will be light and variable and average less than 10KT.


.JKL Watches/Warnings/Advisories...


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