Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 201805

National Weather Service Jackson KY
205 PM EDT Wed Sep 20 2017

Issued at 205 PM EDT WED SEP 20 2017

Shortwave energy continues to pass through the region, helping to
kick off some convection in the far east and even across central
portions of the Commonwealth. The early afternoon update included
some tweaks to our afternoon highs. Also expanded PoPs further
west to account for ongoing convection. Have not seen any
lightning yet but a couple rumbles of thunder can not be ruled
out as afternoon heating and instability increases.

UPDATE Issued at 1055 AM EDT WED SEP 20 2017

Morning fog has lifted and dissipated. Removed morning fog with
update to the forecast package and allowed the Dense Fog Advisory
to expire. Mid level disturbance or short wave is still tracking
through the region today. Models suggest a lobe of energy rotating
through the area this afternoon. Considering this feature combined
with prime diurnal heating, can not rule out some isolated shower
or thunderstorm activity. CAMs seem to be picking up on this and
depict some isolated activity across the area at just about any
time through the afternoon. Have had an isolated shower or two
fire in the east already this morning as well. Went ahead and
increased PoPs across the area for the remainder of the day. With
MUCAPES of around 500 J/kg or higher went ahead and included
isolated thunder for good measure. Grids have been brought in line
with hourly trends and obs. Will reevaluate expanding a slight
PoP further west and tweak afternoon highs with the early
afternoon update.

UPDATE Issued at 638 AM EDT WED SEP 20 2017

Visibilities remain quite poor this morning across the area, and
that means no change to the dense fog advisory. Forecast remains
on track, so will just freshen up the hourly grids for this


.SHORT TERM...(Today through Thursday)
Issued at 355 AM EDT WED SEP 20 2017

Fog has continued to expand this morning and given the trend,
opted for a dense fog advisory. The fog will likely develop into a
stratus layer before breaking up by midday. This suggest we could
see temperatures warm at a slightly slower pace then the past few
days. Still think we should see highs top out in the low to mid
80s despite the slow start. As far as precipitation chances go
today, the main wave has shifted east of the area with the trough
axis sitting over West Virginia. Hi-res models continue to show
most of the development today staying to our east, but did leave
isolated showers in the forecast in the far east as a few showers
could graze these areas. Otherwise, a dry day is anticipated.

Skies will clear off again tonight, setting up another night of
dense valley fog. With a dry day preceding it, fog should not be
quite as widespread, so will only include a mention in the HWO at
this time. The trough axis to the west will weaken and drop
southeast across eastern Kentucky on Thursday. The flow will turn
out of the northeast, pumping in slightly drier air. Despite this,
models show some potential to pop a few showers along the high
terrain in southeast kentucky during the afternoon. Thus, will
include isolated showers in the forecast for far southeast and
south Kentucky. Instability is fairly meager and with heights
building through the day, thunder chances do not look good. Highs
on Thursday will remain mild with readings again into the low to
mid 80s.

.LONG TERM...(Thursday night through Tuesday)
Issued at 355 AM EDT WED SEP 20 2017

The models remain in good agreement with an amplified long wave
pattern to rule across the CONUS. Troughing will control across
the West, while ridging will be found in the East. The ridge will
initially be a larger bubble of high pressure centered across the
Great Lakes and Ohio Valley regions, which will control through
the weekend. By early next week, the combination of the tropical
influence from the western Atlantic, as well as an eastward push
from the trough out west will weaken this ridge. By next Tuesday,
a subtropical high will then build back in across the Gulf of
Mexico, with a ridge axis nosing back in across the Ohio and
Tennessee valleys.

The resultant weather across eastern Kentucky will be dry, with
mostly clear skies and above normal temperatures. Highs will
average in the mid 80s. Lows will average in the lower 60s through
the weekend, before some of the valleys cool off into the upper
50s by early next week.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)

Respectful CU field out there this afternoon but considerably
less coverage in shower activity as compared to yesterday at this
time. Just the same we are seeing convection firing across the
far east and in the south-southwest where there is a bit better
instability and shear. Coverage is not widespread enough to
include mention in the TAFs but will amend should something
threaten any terminals. Otherwise, expecting the redevelopment of
fog overnight, becoming locally dense in places. Expectations are
that fog will not be quite as bad as last night. Followed guidance
closely but tended to go slightly more optimistic overall. Winds
will be light and variable through the entire period.





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