Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 211919
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
319 PM EDT Sat Apr 21 2018

.UPDATE...
Issued at 126 PM EDT SAT APR 21 2018

A nearby surface high across the Great Lakes, and a upper level
ridge axis extending from the Gulf Coast into the Upper Midwest
will lead to tranquil and dry conditions across eastern Kentucky.
This leads to little if any changes needed for this update cycle.

UPDATE Issued at 709 AM EDT SAT APR 21 2018

Areas of valley frost will continue early this morning with
temperatures having dropped into the upper 20s to near 30.
Temperatures will warm above freezing by mid morning and continue
quickly warming through this morning into this afternoon.

&&

.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...(Monday through Saturday)
Issued at 320 PM EDT SAT APR 21 2018

Closed upper level low to our southwest will slowly rotate into
the area Monday into Tuesday. Strong southeast flow will be in
place at the start of the period with some upper level divergence
spreading across the area. Low levels will be tough to saturate
given the strong flow coming off the Smokies, but the upper level
divergence may be enough to produce a hundredth or two of an inch
of precipitation Monday morning. Most of the day should be dry
with the strong southeast flow. With this said, left a window of
higher pops in the morning with the divergence aloft, but went
drier into the afternoon and evening hours as the flow strengthens
and we lose the upper level support. The southeast flow continues
Monday night. Models continue to be generous with the rainfall,
but until the flow becomes more southwest or west later on
Tuesday, we may be hard pressed to get much shower activity. Did
bump highs up a good 5 degrees on Monday with the strong southeast
downslope flow in play. We will see some rain chances on Tuesday
as the upper level low rotates into east Kentucky. A shortwave
trough will act to finally kick things out by Wednesday with rain
chances coming to an end later in the day.

Models are still in great disagreement late next week, but are
trending towards a strong shortwave trough that may bring a period
of rain to the area followed by a decent shot of colder air. Just
how cold depends on the strength of the trough. At this point no
plans to mention any freeze or frost concerns with so much
uncertainty.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
ISSUED AT 126 PM EDT SAT APR 21 2018

A nearby surface high across the Great Lakes, and a upper level
ridge axis extending from the Gulf Coast into the Upper Midwest
will lead VFR condition for this TAF period. Winds will remain
light and variable through the period.

&&

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

$$

UPDATE...DJ
SHORT TERM...GUSEMAN
LONG TERM...KAS
AVIATION...DJ



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