Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 181931
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
331 PM EDT Thu May 18 2017

.SHORT TERM...(This evening through Friday night)
Issued at 331 PM EDT THU MAY 18 2017

Convection has increased in coverage in the southern part of the
forecast area over the past hour, and is greater in coverage than
originally expected. Showers and thunderstorms continue to move
northeast. With that in mind have increased thunderstorm coverage
from isolated to scattered over the southeast part of the forecast
area for the remainder of the afternoon and into the early
evening, while continuing with the isolated coverage in the
northwest.

With the loss of daytime heating the convection should quickly die
off this evening. However, while there is considerable model
disagreement on redevelopment later tonight some of the latest
short range guidance including the HRRR is pointing towards
redevelopment in the southeast late tonight and towards dawn.
This seems to be related to a subtle short wave trough that will
move northeast towards the area late tonight. With this in mind
have decided to go with chance probability area wide late tonight,
with best chances in the southeast.

There is still considerable model disagreement with the extent of
convective development on Friday, though it looks like coverage
should once again be scattered, but with more of the area
affected than this afternoon. Will continue with generally high
chance probabilties for showers and thunderstorms area wide on
Friday.

With more clouds and precipitation tonight through Friday night
there will be less of a diurnal temperature range with highs on
Friday a little lower than today.

.LONG TERM...(Friday night through Wednesday)
Issued at 423 AM EDT THU MAY 18 2017

The models are in good agreement with an overall dynamic long
wave pattern to rule across the CONUS through the long term
portion of the forecast. A persistent ridge across the
southeastern CONUS will be in the process of breaking down by the
start of the weekend, as an upper level low/trough axis moves
from the central Plains into the western Great Lakes region. A
short wave trough moving southeast out of south central Canada
will then help reinforce a deeper trough across the eastern half
of the nation, with another potential upper level low emerging
near the Great Lakes/Ohio Valley by the middle of next week.
Surface features and timing are in decent agreement through the
end of the week, but then breakdown into the early and middle of
next week.

Eastern Kentucky will see increasing moisture out ahead of the
trough to our west and associated cold front. POPs Friday night
and Saturday will be more diurnally influenced, but as the
boundary approaches late Saturday night, chances will increase
even during the overnight period. Best overall POPs continue to be
Sunday afternoon/evening as the cold front marches east across
the region, leading to widespread convection.

The front will exit early Monday morning, with a few showers
lingering in the east. A brief reprieve from the wet weather will
set in from Monday afternoon through Tuesday morning, before
additional height falls move in for Tuesday afternoon, and another
cold frontal passage set to move in for Wednesday. Again,
confidence is lower this far out, so have maintained a more
generalized POP regime. Did introduce some slight chances of
thunder for Wednesday, with some steep low level lapse rates in
place.

Above normal temperatures will continue through the end of the
week, before dropping back to slightly below normal readings for
next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
ISSUED AT 116 PM EDT THU MAY 18 2017

VFR conditions will prevail through the forecast period. However,
extremely isolated showers and thunderstorms will occur this
afternoon and into the evening. With the extremely isolated nature
of any thunderstorms we will not carry thunder or VCTS in the
TAFS for this afternoon. Scattered thunderstorms will be possible
again late tonight into Friday. It is possible coverage could be
higher than today, but at this time confidence in thunderstorms
late tonight into Friday is very low so will leave out of TAFS
for now. Winds will gust from the southwest to around 20 knots
over the northern and western parts of the forecast area this
afternoon with the winds decreasing this evening.

&&

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

$$

SHORT TERM...SBH
LONG TERM...GEOGERIAN
AVIATION...SBH



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