Area Forecast Discussion
Issued by NWS Jackson, KY

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242
FXUS63 KJKL 202007
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
407 PM EDT Sun May 20 2018

.SHORT TERM...(This evening through Monday night)
Issued at 407 PM EDT SUN MAY 20 2018

Have seen a few showers pop this afternoon across the Big Sandy
region as a summertime airmass interacts with the higher terrain.
Temperatures in the mid 80s combined with dewpoints in the mid-upper
60s have created enough instability, that when combined with even
subtle lift, is enough for a pulse type storm to quickly develop.
Have actually seen dewpoints mix down into the upper 50s to lower
60s in the Lake Cumberland region nearer the core of relatively
drier air. Additional showers and isolated storms will remain
possible this afternoon, mainly in far eastern Kentucky where
southwesterly low level winds will provide greater upslope lift.
None of these will last long given the lack of available shear for
storm-scale organization.

Upper ridging currently over much of the southeastern U.S. and
extending into eastern Kentucky will gradually flatten tonight into
Monday as a shortwave trough migrates out of the Great Plains and
toward the Great Lakes. Dry conditions should largely prevail
locally through tonight and early Monday as an overnight complex of
storms remains confined to mainly north of the Ohio River. Valley
fog will be a good bet given crossover temperatures in the mid 60s
or so, but this should be less prevalent than last night due to an
overall lack of rain today.

Rain chances will ramp back up Monday afternoon as upper heights
eventually fall southeast of the above mentioned upper impulse. A
surface low will follow a similar track, surging precipitable water
values back to the 1.5 inch range. A frontal boundary initially near
the lower Ohio Valley will lift north through the morning and
afternoon, but any height falls aloft will be enough to spark
scattered to numerous showers/storms throughout the afternoon given
abundant instability. Anemic deep layer shear will keep strong to
severe storms at bay, other than perhaps a few cell mergers and
resultant brief upticks in updraft strength. These could produce
isolated small hail and wind gusts to 40 mph or so. Rain chances
will continue into the evening and overnight as a cool front slides
southeast toward the lower Ohio Valley.

.LONG TERM...(Tuesday through Sunday)
Issued at 300 PM EDT SUN MAY 20 2018

In the extended we can expect chances for showers and storms
Tuesday through late Wednesday. The best chances for rain during
this initial round of precipitation will be Tuesday afternoon and
evening. The rain should then taper off very quickly late Tuesday
night into early Wednesday morning. The last few showers or storms
should be out of the area by late Wednesday afternoon. After that,
we should see a period of dry weather from Wednesday evening
through early Friday morning, as a ridge of high pressure
temporarily takes hold across the region. A series of low pressure
systems are then forecast to bring periods of showers and storms
back to eastern Kentucky from Friday through Saturday night.
Temperatures during the period will likely be above normal, with
daily highs in the low to mid 80s and nightly lows in the low to
mid 60s expected.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 205 PM EDT SUN MAY 20 2018

VFR conditions currently in place across eastern Kentucky with a
diurnal cumulus field developing near FL030-040. This and light
winds of generally 5 knots or less will mostly diminish this
evening with the loss of daytime heating and mixing. Any shower
and thunderstorm chances will remain very isolated this afternoon
and tonight, with better chances taking place after 18Z Monday
with increasing moisture ahead of a frontal boundary approaching
from the northwest. Fog will likely develop again tonight into
Monday morning, reducing visibilities to IFR or worse at times.
This should not be as prevalent as that which occurred last night
and this morning due to a lack of rainfall today, but will likely
still see some outside of valleys given the degree of low level
moisture in place and near calm winds tonight. This should mix out
by mid Monday morning as heating allows for increasing clouds into
the afternoon.

&&

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

$$

SHORT TERM...GUSEMAN
LONG TERM...AR
AVIATION...GUSEMAN



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