Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 271832

National Weather Service Jackson KY
232 PM EDT Thu Jul 27 2017

Issued at 1222 PM EDT THU JUL 27 2017

Most significant area of precip is about to exit the eastern part
of the forecast area, after having tracked across the north.
Additional scattered showers/t`storms were ongoing across the
area, but the coverage is much less. Overall suggestion in the
mesoscale models from this morning is that the best shot at good
coverage of precip later this afternoon is in the northern part of
the area, but confidence in the evolution of convective
development is not very high.

UPDATE Issued at 1033 AM EDT THU JUL 27 2017

Showers/t`storms have become fairly widespread over the northeast
portion of the area, and the POP has been increased for that area.
Forcing mechanisms are weak, and nailing down when where
development will occur is difficult today. Will need to further
examine trends and latest model runs to see how morning convection
may impact the outcome this afternoon.

UPDATE Issued at 700 AM EDT THU JUL 27 2017

The forecast remains on track so far this morning. A few showers
and storms will be moving across the area early this morning.
These will gradually increase in coverage as the morning wears on,
and should be widespread across the area by this afternoon. The
best chance for rain will be from this afternoon through tomorrow,
as a cold front slowly moves across the region. Other than using
the latest obs and short term model data to freshen up the hourly
forecast grids, no changes to the forecast were necessary.


.SHORT TERM...(Today through Friday)
Issued at 311 AM EDT THU JUL 27 2017

A few rain showers have formed during the overnight, and should be
moving into the area between 7 and 8Z. These should remain
isolated to scattered through early this morning. This activity is
likely firing up due to the presence of a weak low level jet. A
few thunderstorms should begin forming across the area after the
sun has been up for a couple of hours and some heating begins to
occur. Through out the day today we can expect scattered showers
and storms to increase in coverage as a cold front approaches
from the north. The most widespread rain is anticipated tonight
and Friday, as the cold front moves slowly across the region. Due
to the high moisture content of the atmosphere, and the presence
of the front, locally heavy rainfall will be possible at times,
especially with stronger thunderstorms, or anywhere that multiple
storms move repeatedly across the same locations. Based on the
latest model data, the best potential for heavy rainfall should
be from late this afternoon through tonight.

Temperatures today will range from slightly below normal values
north of the Hal Rogers Parkway, to slightly above normal values
south of there. We can expect a dramatic cool down on Friday as
the front moves through the area and widespread clouds and rain
push across the region. Highs on Friday will likely only make to
around 80.

.LONG TERM...(Friday night through Wednesday)
Issued at 350 AM EDT THU JUL 27 2017

The models are in good agreement with an amplified long wave
pattern to remain in place through the majority of the period. An
upper level low will be cutting off as it moves from the Great
Lakes/Ohio Valley into the mid-Atlantic by this weekend, while
ridging rules across the West. This will allow for a much more
pleasant air mass across the Ohio and Tennessee valleys by this
weekend and into early next week. Troughing will remain across the
eastern CONUS through the middle of next week, with surface high
pressure eventually shifting off to the east, allowing for a
gradual increase in temperature and humidity across the region.

Showers and thunderstorms will likely be ongoing Friday evening,
as a surface cold front sags southeast across the area. Thunder
chances and locally heavy rains will be ending by around
midnight, with the threat of showers continuing into Saturday
morning, as a cutoff low deepens to our east, and the low level
flow veers to the northwest. Dry weather will return by Saturday
evening and looks to last through Wednesday morning, as surface
high pressure builds in and low level winds remain out of the
northeast. By Wednesday, the high will break down a bit and shift
to the east, allowing for return flow. This will result in a few
showers and storms threatening the Tennessee/Kentucky border by
the afternoon.

Temperatures will be cooler through the weekend, with highs in
the mid and upper 70s on Saturday, lower 80s Sunday and Monday,
and then gradually warming back to seasonal normals in the mid 80s
for Tuesday and Wednesday.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)

It`s a difficult forecast for aviation, due to a high lack of
confidence in specifics over the next 24 hours. Showers/t`storms
are expected at times, but exactly when is the question. Have only
used a generalized forecast in the TAFs, with precip being most
likely tonight into Friday, and the worst conditions overall on
Friday. If specifics become more apparent, they will need to be
included in later issuances.




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