Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 251923
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
323 PM EDT Tue Jul 25 2017

.UPDATE...
Issued at 1154 AM EDT TUE JUL 25 2017

Temperatures have been slow to warm where clouds lingered the
longest, but will warm more quickly once the clouds dry up.
However, being that it is already noon, a full recovery to what
would have occurred without clouds is less likely, and max temps
have been adjusted down slightly for areas with the peskiest
clouds.

UPDATE Issued at 948 AM EDT TUE JUL 25 2017

Clouds are stubbornly holding on over the southern portion of the
area. They are still expected to break up today, but it`s going
to take longer than was previously forecasted, and the outlook has
been updated to reflect this.

UPDATE Issued at 700 AM EDT TUE JUL 25 2017

Although the front has helped to clear out the fog from the more
open areas and ridges, it is holding on in the river valleys -
likely dense in spots. This shows up well on the nighttime
microphysics composite channel of GOES 16. Have fine tuned the sky
cover and fog coverage for the next couple of hours and also
updated the T/Td grids per the latest obs and trends. These have
been sent to the NDFD and web servers.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 355 AM EDT TUE JUL 25 2017

07z sfc analysis shows a summertime cold front dropping south
through eastern Kentucky. This is attempting to bring drier air
into the JKL CWA on light north to northeast winds. This is also
helping to keep the fog in check north of the Mountain Parkway
while locations to the south are still experiencing patchy fog
with likely some locally dense spots in the sheltered southern
valleys. Temperatures currently are varying from the mid 60s north
to the lower 70s in the south. Meanwhile dewpoints are running in
the low 60s far north to the upper 60s and lower 70s south.

The models are in good agreement aloft through the short term
portion of the forecast. They all depict rising heights over the
region as a large area of ridging spreads in from the southwest.
This occurs in the wake of a departing trough over the Northeast.
Weak energy packets will slide southeast in the mid level
northwest flow through the Ohio Valley but stay too far north to
have much of an effect on Kentucky in the rising heights
environment. Given the agreement have favored a general model
blend through Wednesday evening.

Sensible weather will feature patchy fog along with some local
dense spots dissipating by mid morning with a drier and somewhat
more comfortable afternoon for most places thanks to high pressure
and a change of air mass. Look for a quiet night to follow with
temperatures about a category cooler than early this morning and
any fog likely confined to the deeper river valleys. Wednesday
will be a bit warmer than today and humidity levels will climb as
the front to the south starts to work back north with returning
moisture. Can`t completely rule out a shower or storm in the far
southwest for Wednesday afternoon, but in all likelihood the
entire area will be dry through Wednesday evening.

Again used the CONSShort as the start for the forecast grids with
only minor point adjustments made to lows and highs. Basically
zeroed out PoPs for all but the Cumberland Valley today and
Wednesday.

.LONG TERM...(Thursday through Tuesday)
Issued at 323 PM EDT TUE JUL 25 2017

The extended portion of the forecast begins on Thursday with an
amplified upper level pattern for this time of year. With a stout
ridge in place over the western CONUS, a shortwave will drop
southeast through the Midwest into the OH valley for Thursday as a
surface cold front will push southeast into the area. Good low
level moisture and temps rising into the mid 80s, will mean a good
chance for showers and thunderstorms by Thursday afternoon as the
front approaches. In fact, instability will suggest a slight
severe potential with the main threat being wind as the freezing
level will likely be pretty high for any hail development. Model
soundings would suggest more of a downburst threat with some DCAPE
values preset. Thursdays activity will wane into the night.
Renewed convection will be likely as well into the day on Friday
with a slowed boundary draped over the area will be enough for
another round of convection Friday afternoon. Less instability
though for Friday afternoon will mean a lesser severe threat if
any.

After the last of the forcing or whats left of the boundary exits
southeast and southern KY by Friday night, a period of dry weather
will settle in. Aloft, the mid level ridge axis will shift east
over the area in conjunction with a surface bubble of high
pressure will keep eastern Kentucky dry for the rest of the
extended. In addition to this pattern, the lack of a return flow
in this pattern will allow for cooler temps and less muggy
conditions than what we have seen heading into the start of next
week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
ISSUED AT 259 PM EDT TUE JUL 25 2017

Aside from late night and morning fog, VFR conditions will
prevail through the period. Fair weather cumulus present at the
start of the period will dry up this evening. Fog will develop in
valleys late tonight and spread in breadth and depth until
sunrise, and will then dissipate on Wednesday morning. Localized
VLIFR can be expected in the fog. TAF sites are expected to be
affected to varying extents.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...HAL
SHORT TERM...GREIF
LONG TERM...SHALLENBERGER
AVIATION...HAL



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