Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 252203
AFDJKL

Area Forecast Discussion
National Weather Service Jackson KY
603 PM EDT MON JUL 25 2016

.UPDATE...
Issued at 603 PM EDT MON JUL 25 2016

WSR-88D radar shows convection continuing mainly south of a line
from Pikeville, to Jackson, to McKee this hour. Expanded pops for
a short period of time, but much of this will be diurnally
driven and should continue a downward trend. Also locations north
of this have been scoured out by earlier convection and outflow
boundaries. CAMS have about as good of a handle on the convection,
as one would expect and therefore no preference on any one model.
Temperature curve has been difficult to pin down given the
coverage of storms and outflow boundaries. Mostly went toward a
blend approach with current obs and trended into the evening. The
GLAMP seems to have the overall best curve at the moment in terms
of guidance. Otherwise no major changes needed at this point.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 317 PM EDT MON JUL 25 2016

Showers and thunderstorms continue to erupt this afternoon, with
the best concentration occurring over our northern counties closer
to a weak frontal boundary paralleling the Ohio River. This
boundary will remain fairly stationary just to our north and
remain a focusing mechanism for scattered to numerous showers and
thunderstorms. While the storms should exhibit a diurnal trend,
with coverage peaking in the afternoon hours, cannot rule out a
storm at any time over the next 36 hours.

The main threat with storms will remain heavy rainfall and
lightning in the high CAPE but low shear environment. Storms seem
to want to move along fairly well at 10 to 15 mph and that is a
good thing considering PWATS are approaching 2 inches. However,
there will be a minor threat for flash flooding in areas that see
repeating rounds of thunderstorms. We are also seeing storms today
gust out pretty easily and an isolated severe storm remains
possible this afternoon with DCAPE exceeding 1000 J/kg.

With the front remaining to our north through the period, the
airmass over our region will remain very muggy with dewpoints
staying well into the 70s. Increased clouds and showers during the
day tomorrow should keep temperatures below 90 for most areas, and
heat indices below 100 for a change.

.LONG TERM...(Wednesday through Monday)
Issued at 317 PM EDT MON JUL 25 2016

Models are in reasonably good agreement with general mid/upper level
flow and larger scale synoptic features through the period. But
significant differences are beginning to crop up with respect to
details of embedded disturbances within the general flow pattern and
corresponding sfc features thereby lowering overall confidence of
the extended package, particularly with respect to sensible weather.
Somewhat zonal flow quickly amplifies with a mean trough forming
over the Great Lakes and Mid-West which remains in place across the
region through the period. Rather significant ridging does develop
aloft and replaces this eastern CONUS trough as it lifts northeast
out of the region just beyond the end of the extended window.

At the surface, it appears that a nearly stationary frontal boundary
will exist somewhere across the northern portions of the
Commonwealth. This feature will provide a focus for the bulk of our
sensible weather through the extended in the form of showers and
thunderstorms. However, main concern revolves around a sfc wave
tracking through the region Thursday into Thursday evening. The last
three runs of the GFS have been quite consistent with this wave that
develops and moves across the Commonwealth. The GFS advertises PWATs
increasing to between 2 and 2.25 inches during this window. In
addition, freezing levels increase to between 14 kft and 15 kft AGL
with moderately high CAPEs of 1000-1500 K/kg and LCLs between 500
and 1000 ft AGL. Should this scenario pan out there is a potential
for some warm water processes. And while storm motions are
considerable at 15-25 kts, flow aloft would be favorable for
training along the sfc boundary wherever it eventually sets up.
Consequently hydro issues may become a concern by Thursday. The 0Z
ECMWF suggest a similar potential but carries the surface wave
further north and west of our forecast area thereby keeping the
heavy rain threat north of the Ohio River. A quick look at the 12Z
ECMWF shows that it has trended slightly towards the GFS solution.

With a mean trough over the eastern CONUS and expected rounds of
mainly diurnal precipitation, daily high temperatures should be
cooler than we have been experiencing, much closer to the mid 80
norms for this time of year. However, conditions will also be quite
muggy keeping overnight lows in the upper 60s to near 70. Thus
diurnal swings will be limited as well.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 138 PM EDT MON JUL 25 2016

Scattered thunderstorms continue to erupt in a sultry airmass.
These will likely remain rather hit and miss and will maintain no
more than a VCTS mention in the TAFs for now. Expect these storms
to exhibit a diurnal trend and diminish in coverage slowly after
sunset, although there will be a small threat for a shower or
storm anytime through the night and into tomorrow morning due to a
frontal boundary sagging southward toward our area. Fog is another
concern but it should remain patchy and is likely to only affect
TAF sites that are hit directly by a thunderstorm this afternoon.
With that in mind, will go with VFR TAFs for now through 18z
Tuesday and let later shifts fine tune.

&&

.JKL Watches/Warnings/Advisories...
None.
&&

$$

UPDATE...DJ
SHORT TERM...ABE
LONG TERM...RAY
AVIATION...ABE



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