Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 230000 AAA

Area Forecast Discussion...UPDATED
National Weather Service Jackson KY
800 PM EDT MON AUG 22 2016

Issued at 730 PM EDT MON AUG 22 2016

23z sfc analysis shows a very pleasant evening underway beneath
a broad area of dry high pressure centered just to the east of the
CWA. This has resulted in clearing skies as some mid level cu
beneath some higher cirrus start to fade out with the loss of
daytime heating. Expecting mostly clear sky through the night and
into Tuesday morning. However, patchy fog will likely develop
again in the valleys with the spots nearest the rivers and lakes
in store for some localized dense fog around sunrise. Have fine
tuned this idea in the forecast Wx grids along with some
adjustments to the Sky ones over the next 6 to 12 hours. As for
temperatures, anticipate a pretty solid ridge to valley split to
set up given the clearing skies, light winds, and decent dewpoint
depressions. See evidence of this already, prior to sunset, with
the ridges, and more open areas, reporting temperatures in the mid
70s while some sheltered valleys are around 10 degrees cooler.
Dewpoints, meanwhile, are in the mid to upper 50s most places -
slightly more moist in the western Cumberland Valley and along the
Tennessee border. Winds are light to calm through eastern Kentucky
at 7 pm. The updated grids have been sent to the NDFD and web


.SHORT TERM...(This evening through Tuesday night)
Issued at 357 PM EDT MON AUG 22 2016

Straightforward forecast for the short term. Dry, relatively
pleasant weather dominates the headlines. We will see a gradual
increase in heights aloft through the period as short wave ridging
builds into the Ohio Valley and the all too familiar Bermuda High
once again begins to exert its influence across the southeastern
CONUS. Return flow will bring a slight increase to the humidity
levels by late Tuesday into Tuesday night. For sensible weather
our main forecast challenge will be temps, dew points, and the
potential for fog. Much drier air has mixed into the boundary
layer this afternoon with dew points at a few locations dipping
into the low 50s. Dew points will recover somewhat after sunset,
but low crossover temps will make it much more difficult to
realize any widespread dense fog. Best opportunity will be for
those locations closer to some source of water such as our river
valleys. Bottom line...overnight fog should not be as widespread
as this morning`s, and a little worse than tomorrow night into
early Wednesday morning as our temps begin to moderate. Highs
Tuesday will climb into the mid 80s for most areas. Overnight
lows will be quite refreshing as we bottom out in the mid to
upper 50s.

.LONG TERM...(Wednesday through Monday)
Issued at 257 PM EDT MON AUG 22 2016

High pressure which has encompassed the Ohio River Valley during the
short term will finally start pushing east of the region by
Wednesday morning at 12Z. While still in control, this will allow
return southerly flow and warming moistening conditions across the
region. High temperatures will find themselves back into the mid 80s
with higher humidity values Wednesday afternoon. Meanwhile, a closed
low will be rotating through along the central Canadian/US border.
This will slowly lose strength and dissipate as strong upper level
ridging holds tight across the southeast conus through Thursday,
blocking further forward propagation. At the surface a low pressure
system will traverse along the path of this upper low, along the
central US/Canada border, pulling a cold front southeast across the
plain states. As the upper level low becomes blocked from eastward
movement and loses strength, the surface low will also lose forward
propagation and the cold front will start to shear out.

So what does this mean for eastern KY? With our location between the
incoming cold front, and the return flow of the exiting high
pressure system, the stage will be set for possible convection.
However, with upper level ridging still in predominate control, all
forcing will be limited to the low levels with little upper level
dynamics. Both the GFS and ECMWF bring some isolated pops into the
region Wednesday afternoon, and continued the isolated to scattered
convection through Thursday. However, the location and timing of
this is still somewhat very uncertain. The frontal zone finally
progresses southeast through the state late Thursday night and into
the day Friday. But even then, the lack of forcing, in addition to
two strong high pressure centers on either side of the frontal
boundary, will keep pops at a isl/sct minimal, with only light QPF

Temperatures will modify little during this period, with no strong
wind shifts in place. Expect mid and upper 80s with decent humidity
each day into the weekend. High pressure should take hold post
frontal Saturday and Sunday, however the GFS and ECMWF are showing
varying solutions, with the GFS still trying to allow for convection
across the region. Given the uncertainty this far out in the
forecast, will continue with the model blend for pops and QPF
during this time, which keeps the CWA relatively dry.


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)

VFR conditions expected through the period. The exception to this
will be the deeper valley locations where late night, early
morning fog will develop again. With drier air settling down
across the region do not expect the fog to be as prevalent tonight
as it was this past morning except in the river valleys.
Consequently, KSME, KLOZ, KSJS, and KSYM visibilities will likely
be affected for a few hours through the pre-dawn hours Tuesday
and as such went with a short period of MVFR/IFR VSBYS, 08-12Z.
Did also allow for a tempo of denser fog affecting KSME for a time
pre-dawn. Winds will generally be light and variable through the
period thanks to high pressure in place.


.JKL Watches/Warnings/Advisories...


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