Area Forecast Discussion
Issued by NWS Jackson, KY

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000
FXUS63 KJKL 210800
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
400 AM EDT Sat Apr 21 2018

.SHORT TERM...(Today through Sunday)
Issued at 400 AM EDT SAT APR 21 2018

High pressure continues to assert itself across eastern Kentucky
with only a few strands of cirrus streaming in.  These will increase
through the day downstream of an upper level low pressure system
currently churning overtop Denver. Shortwave ridging will nudge
eastward across the Commonwealth as it flattens, but
heights/thicknesses will nonetheless increase as subsidence keeps
dry conditions in place and leads to further warming this afternoon
with highs topping out in the mid-upper 60s north of Mountain
Parkway and low-mid 70s south.

Light north/northeast winds will veer a bit more easterly tonight in
response to surface ridging across the Great Lakes to mid-Atlantic
coast crawling eastward. While cloud cover will gradually
thicken/lower tonight, valleys in the Big Sandy region should still
see a sizable dropoff in temperatures, cooling to the mid 30s. A
few areas of frost will thus be possible once again along with some
patchy valley fog.

The previously mentioned upper low will dig south across the
southern Plains and into the lower Mississippi Valley Sunday with an
attendant surface low immediately downwind. Increasing precipitable
water values and at least mid clouds will stream northeast into the
Lake Cumberland region. Still some uncertainty as to how much the
upper low will dig and subsequently how fast it will shift east,
keeping the best rain chances southwest of Kentucky through the day.
Downslope winds will aid in maintaining a dry near-surface layer,
but will still keep low-end PoPs in for the Lake Cumberland region
and far southeast Kentucky. Any rain that does occur through the
afternoon will be light at less than one tenth of an inch, prior to
better chances taking shape into early week.

.LONG TERM...(Sunday through Friday)
Issued at 336 PM EDT FRI APR 20 2018

A upper level ridge axis will still be extending across the Ohio
and Tennessee Valleys Sunday. This will help slow the progression
of rain showers activity northward and still may be too quick on
the progression northward overall. Did opt to adjust from what the
blended data provided for Sunday, but tried to remain match up
with the neighboring offices. The NAM is the wetter outlier this
afternoon for Sunday into Sunday night and this could be some
influence in the blended data. This southern stream upper level
low will remain the culprit for unsettled weather across the Ohio
and Tennessee Valleys through much of the period. This southern
stream system will eventually phase with a northern stream upper
level wave, but the guidance diverges greatly at this point on the
depth and forward progression of the northern stream feature. This
leads to a low confidence forecast from midweek onward. The slight
to chance POPs provided by the blended guidance seems reasonable
at this point and therefore little changes were made to the
forecast for this period. In general, the temperatures through the
long term will remain near normal for this time of year.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
ISSUED AT 133 AM EDT SAT APR 21 2018

VFR conditions to continue with generally northeast to southeast
winds of less than 10 knots.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
Frost Advisory until 9 AM EDT this morning for KYZ044-050>052-
058>060-068-069-079-080-083>088-104-106>120.

&&

$$

SHORT TERM...GUSEMAN
LONG TERM...DJ
AVIATION...GUSEMAN


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