Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 210005 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
805 PM EDT Sun May 20 2018

.UPDATE...
Issued at 805 PM EDT SUN MAY 20 2018

Eastern Kentucky remains precipitation-free at the moment, as
short wave ridging has kept most convection at bay. A cluster of
storms is moving in from around the Ohio River, but these should
dissipate as they move into a less favorable environment across
the Bluegrass, which recent runs of the HRRR supports. Will
maintain the dry forecast through the night, and have mainly
freshened up the diurnal temperature drop off through this
evening. Will assess temperatures and fog a bit later. Updates
will be out shortly.

&&

.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 00Z TAFS through 00Z Monday evening)
ISSUED AT 805 PM EDT SUN MAY 20 2018

Expect VFR conditions to prevail through the majority of the
period. Fog will likely form again late tonight, but expect the
IFR or worse conditions to be more confined to the deeper river
valleys, given the lower crossover temperatures as well as lack of
precipitation coverage through the day. Have included a 2 to 4
hour window of MVFR fog at the TAF sites, generally between 09 and
13z. Storm coverage looks to be better on Monday, and will
include VCTS at all sites during the afternoon hours. Winds will
remain at around 5 kts or less through the period.

&&

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

$$

UPDATE...GEOGERIAN
SHORT TERM...GUSEMAN
LONG TERM...AR
AVIATION...GEOGERIAN



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