Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 181329

National Weather Service Jackson KY
929 AM EDT Tue Jul 18 2017

Issued at 929 AM EDT TUE JUL 18 2017

Satellite shows the valley fog has burned off. Have updated NDFD
and associated products for latest observational trends though
this only resulted in minor changes to the hourly forecasts.

UPDATE Issued at 648 AM EDT TUE JUL 18 2017

Made some minor adjustments to the temps based on the current
observations. Also made some adjusted the diurnal curve throughout
the morning to better show the warming transition from this
mornings lows. Also loaded in the latest observations for dew
points and winds. Seeing a few observations of fog across the
region, but nothing dense, so will kept with patchy fog mention
over the next couple of hours. Otherwise, light winds and clear
conditions are holding strong. All changes have been published and
sent to NDFD/web.


.SHORT TERM...(Today through Wednesday)
Issued at 356 AM EDT TUE JUL 18 2017

As a strong upper level ridge continues to expand eastward into
western and Central Kentucky today, a shortwave will transition
into a closed low over the Carolinas. This closed low will slowly
make a shift eastward toward the Atlantic coast through the short
term period as heights continue to rise across Kentucky. At the
surface, a dying stationary boundary will remain draped across the
northern extent of the state, near the Ohio River. This is
expected to fizzle out completely through the day today. High
pressure will then be found across the remainder of the state.

Temperatures are expected to continue their above-normal trend in
response to this building ridge. Most locations could brush 90
degrees for highs today, with similar temperatures in the upper
80s to near 90 expected for Wednesday afternoon as well.
Conditions should also remain mostly clear and dry throughout the
short term. These clear conditions will once again prompt some
good ridge/valley temp differences overnight. Fog will also be
present in the valleys, however with continued lack of moisture
over the last few days, the extent and severity of this fog will
continue to diminish, so only mentioned patchy wording.

The only caveat to this benign pattern will be the potential for
an isolated thunderstorm along the VA border during the afternoon
today. Deeper southerly flow across central the Appalachians and
points eastward interacts with the upper level energy in place,
with convection potentially expanding across the high terrain and
into portions of eastern KY. By Wednesday, this system will have
pushed just enough eastward to alleviate any further chances
across east KY.

.LONG TERM...(Wednesday night through Monday)
Issued at 436 AM EDT TUE JUL 18 2017

We will initially be on the periphery of a strong mid/upper level
ridge over the south central CONUS, with surface high pressure
over our area. This will likely keep our weather dry at least
through Thursday. The NAM is showing some precip making it as far
south and west as our area during this time, but is not supported
by the operational GFS or ECMWF. There are a small number of GFS
ensemble members with some light precip. While the POP is not
zero, a value below the 20% threshold for inclusion of precip in
the forecast seems the most appropriate.

Ridging at the surface and aloft should break down Friday through
the weekend. In the upper levels, this will allow for slight
cooling and a modest increase in wind as the westerlies drop
further south. At the surface, increased flow will help to bring
Gulf of Mexico moisture into the area. The combined result will be
a better chance of showers and thunderstorms. A cold front is
expected to approach from the northwest Sunday and Monday, and
this is when the highest POP will be carried (in chance category).

Conditions will be uncomfortably hot and humid during the period.
The highest temperatures are expected on Friday, before the
increase in clouds and precip starts to hold temperatures down.


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

VFR conditions will prevail through the majority of the period,
as high pressure remains in control. IVFR or worse fog may be
present in the deeper river valleys through 13z. SME just dropped
to below airport mins as the fog in the valley below has now
lifted and propagated into the TAF site. Based on the same
occurrence yesterday, will keep SME below airport mins through
13Z, around which point they should clear out. Otherwise, some
diurnally driven cumulus ranging from 4-5k feet agl will be seen
across the area during the afternoon, dissipating in the evening.
Winds will remain light and variable. Calm and clear conditions
tonight will once again promote fog development in the deeper
valleys to round out the TAF period, but with continued dry
conditions in place, moisture will be more limited and impacts
should continue to be less than nights before. Don`t expect this
fog to impact TAF sites.




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