Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 221845
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
245 PM EDT Thu Jun 22 2017

.UPDATE...
Issued at 149 PM EDT THU JUN 22 2017

Freshened up the hourly POPs through the rest of the day.
Widespread showers will continue to gradually overtake the area.
Increased confidence in the heavy rainfall potential for Friday
afternoon through early Saturday morning based on some of the 12z
data has also prompted the issuances of a flash flood watch.
Updates have been sent.

UPDATE Issued at 1130 AM EDT THU JUN 22 2017

Mainly light rain showers continue to advance northeast into
eastern Kentucky. There has been no lightning activity upstream in
Tennessee, and given the weak low and mid level lapse rates, will
only allow for a slight chance of thunder for the rest of the day.
Have also lowered the highs somewhat, with thicker cloud cover
advancing in quickly. Highs look to range from the mid 70s across
the southwest, to around 80 to the northeast. Updates have been
sent.

UPDATE Issued at 755 AM EDT THU JUN 22 2017

Showers on the leading edge of significant moisture increase from
the Gulf into the southeast and TN Valley has reached as far
north as middle and eastern TN. High clouds have also been
increasing as have mid level clouds in the south. The current
forecast pops still look on target compared to recent hi res
guidance and 6Z models runs. The only changes at this time were
minor adjustments to hourly temperatures and sky conditions based
on recent observations and satellite trends.

&&

.SHORT TERM...(Today through Friday)
Issued at 445 AM EDT THU JUN 22 2017

Early this morning, a rather zonal pattern in nature is in place
across the northern Conus with a ridge centered over the Desert
Southwest and another ridge centered between the Bahamas and
Bermuda. Surface high pressure in place from the Appalachians to
the Carolinas. Meanwhile, Tropical Storm Cindy is gradually
nearing the Gulf Coast near the TX and LA border. Tropical
moisture is already moving north across the Southeast and string
to surge north toward the TN and OH Valley regions. Despite an
increase in mainly cirrus with a few mid clouds, a moderate
nocturnal inversion has developed with ridgetops around 70 or the
lower 70s and valleys in the 60s. Valley fog was present in a few
valley locations.

At the same time that Tropical Storm Cindy and eventually its
remnants track toward the Arklatex region through this evening,
return flow between it and departing high pressure will bring a
plume of Gulf moisture north into the East KY. In addition, a
shortwave trough will move into the Northern Plains and approach
the Great Lakes tonight. A preceding cold front should move into
the Central Great Lakes by dawn on Friday and approach the Lower
OH Valley. Meanwhile the center of the remnants of Cindy should
reach southeastern AR by dawn on Friday. The shortwave trough
should move into the Great Lakes on Friday with the trough axis
nearing the Lower OH Valley. Also, the cold front should approach
the area from the north at that point.

A round of showers and a few thunderstorms is expected across the
region, arriving around midday into the afternoon in the south
and then spreading northeast through evening. The deeper moisture
should arrive first in the southwest and this combined with less
influence of a downslope southerly flow in the low levels will
lead to heavier rainfall there today. The chances for locally
heavier rain from thunderstorms will also be greatest across the
southwest or west this afternoon and evening. This rain will
occur with some isentropic lift on the leading edge of moisture
gradient as PW climbs rather dramatically to the 1.95 to about
2.1 inch range by sunset. Some solar insolation may also aid in
some shower and thunderstorm development.

Scatter to possibly numerous shower chances will continue into the
overnight tonight and into Friday morning as the front and
shortwave trough approaches and interacts with moisture from the
remnants of Tropical Storm Cindy. The threat of heavy rain should
return again on Friday afternoon as the center of the remnants of
Cindy nears and interacts with some daytime heating. A period of
some dry slotting or drier air moving at mid and upper level
should work across the area in between the rounds of rain and
allow for heating on Friday to warm temperatures to around 80 or
the lower 80s. At the same time, moisture will again increase
from the south and west and band of showers and some thunderstorms
are possible as the approaching front, trough, and circulation
form the remnants of Cindy near. This circulation should locally
enhance low level shear and this combined with daytime heating in
potential bands of convection will bring a chance for a few
strong to possibly severe thunderstorms along with heavy rain.
Damaging winds would be the main threat although with the
increased shear in the afternoon to early evening, a stray weak
tornado cannot be ruled out.

The heavy rain threat will continue to be highlighted in the HWO
as well as an ESF. The threat for a couple of strong to severe
storms is also highlighted in the HWO. If current trends continue,
a Flood Watch will likely be needed for Friday into Friday night.
Uncertainty remains in exact placement of the axis of axises of
heaviest rainfall, but one could develop by the long term period
over east KY with another closer to the approaching front.

.LONG TERM...(Saturday through Thursday)
Issued at 244 PM EDT THU JUN 22 2017

The extended portion of the forecast begins on Saturday with the
upper level pattern featuring a stout ridge over the western CONUS
transitioning into a trough over the Great Lakes. The first wave
associated with the combination of tropical moisture and a cold
front will finally exit the area at the start of the forecast
period. So will see a chance of showers over eastern Kentucky
through the day on Saturday as the last of the showers exit the
area by the evening. This will usher in a dry period as models
have trended drier and drier. The mentioned stout ridge in the
west will build as it shifts east nudging the axis over the
Midwest by Wednesday. In addition, a bubble of surface high
pressure will carve out an area of subsidence over eastern
Kentucky and much of the central Appalachians. In fact, the
airmass intrusion behind Cindy will bring some welcomed cooler
temps to start next week with highs in the 70s expected through
Wednesday.

One difference in the forecast might be on Monday afternoon as the
most recent 12Z Euro and GFS has brought a weak wave dropping far
enough south to bring a small chance of showers and a
thunderstorm. This is a change to the model trends so am more
inclined to keep the dry forecast inherited from the super blend.
Otherwise, the extended features dry weather and slightly cooler
high temperatures.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
ISSUED AT 149 PM EDT THU JUN 22 2017

Showers and MVFR ceilings at the leading edge of the moisture
advection associated with Tropical Storm Cindy will continue to
advance northeast across the region. Ceilings then look to raise
up this evening, before potentially lowering again towards dawn.
Shower chances will be diminishing from southwest to northeast
this evening, as the first surge of moisture exits off to the
northeast. Low level wind shear will threaten later tonight, as
850 mb winds remain around 40 to 50 kts, while south to southeast
winds at the surface remain at around 5 kts or less. There will at
least be a threat of scattered showers and a few thunderstorms
into Friday, as the cold front begins to move in from the
west and northwest.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from Friday afternoon through Saturday morning
for KYZ044-050>052-058>060-068-069-079-080-083>088-104-106>120.

&&

$$

UPDATE...GEOGERIAN
SHORT TERM...JP
LONG TERM...SHALLENBERGER
AVIATION...GEOGERIAN



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