Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 202351 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
751 PM EDT Thu Apr 20 2017

.UPDATE...
Issued at 631 PM EDT THU APR 20 2017

A broken line of showers and thunderstorms is attempting to make
it in from central Kentucky. Most of this activity is diminishing
as it is heading east, and all of the convection across eastern
Kentucky has dried up, thanks to dew points in the lower to mid
50s, with a few upper 40 degree readings noted. As such, have
delayed the POPs somewhat in the east and kept it dry until the
cold front moves in closer later tonight. Skies have also
thinned, and will allow for a bit of decoupling in the eastern
valleys this evening. Updates have been sent.

&&

.SHORT TERM...(This evening through Friday night)
Issued at 428 PM EDT THU APR 20 2017

Ongoing isolated showers and thunderstorms are expected to continue
to wain during the rest of the afternoon as we await an incoming
cold front overnight. It is along and just ahead of this cold front
that we will find our next best chances for precipitation across the
CWA, including thunderstorm potential. Latest NAM12 forecast
soundings are still showing soundings becoming saturated throughout
the column after 6Z (first in the north and a few hours later in the
south), giving good support for likely to numerous coverage. That
being said, CAPE values aren`t looking that great, generally between
400 and 700 j/kg overnight, with very little llvl wind shear and
moist upper levels that would deter any hail potential. As such,
expect this to be more of a localized heavy rain event, with some
good lightning based on the intensity of the rain...but otherwise
not expecting much in the way of high winds (wind speeds aren`t very
impressive aloft) or hail.

Thunderstorms may intensify slightly during the first half of the
day Friday across the southern CWA as the front continues southward
through the state. As temps warm through the morning with southerly
flow, this will help to boost CAPE values above 1000 j/kg, with LI`s
falling to -4 across the central and southern CWA. Some low level
wind shear will also be present with southerly winds near the
surface and westerly flow in the mid and upper levels. All together,
thunderstorms will likely be more prominent in coverage and strength
tomorrow with some gusty winds and small hail not to be ruled out.
However still think the main threat will be localized heavy rains
and lightning. In the northern CWA the front will have already
passed, so while showers and thunderstorms are still possible, they
will likely be elevated in nature given more northerly flow moving
in at the surface.

By the latter half of the day, the front will have sagged just south
of the state, where it will stall out through Friday night. This
will keep enough moisture over the region to promote continued
widespread precipitation. However, with northerly flow in the low
levels on the north side of the front, we will not see much in the
way of instability or thunderstorm potential. As such, have
thunderstorms decreasing Friday evening, and kept out all mention of
thunder from Friday night through Saturday morning. While
temperatures should still reach the upper 60s to mid 70s during the
day Friday despite cloud cover and precip in place, northerly winds
behind the system will cool the airmass down substantially, dropping
to the upper 40s to mid 50s for Saturday morning lows (coolest in
the north).

.LONG TERM...(Saturday through Thursday)
Issued at 430 PM EDT THU APR 20 2017

The period will begin with a trough extending from Quebec southwest
into the mid MS Valley and lower MO Valley region with riding
extending from parts of the Eastern Pacific north into the Western
Conus. At the surface, a wave of low pressure is expected to track
along a boundary that will have stalled out to the south of the
region during the near term period. This low will slowly track
toward the Carolinas through Sunday evening while the southwestern
end of the upper trough closes off into an upper level low and moves
across the Lower OH Valley and into the TN Valley and southern
Appalachians through the weekend. This upper low should meander into
the Southeast and finally off the southeast coast for Monday into
Tuesday. In its wake, an upper level ridge will build into the
Southern Plains and lower OH Valley Sunday night into Monday.
However, this ridge will dampen beyond Monday as a broad trough
develops from the Western Conus into the Central Conus through
midweek. Late in the period, a shortwave trough moving from the
Plains into the Great Lakes should generally track northwest of the
area with an associated surface boundary briefly approaching the OH
Valley at midweek. However, another shortwave moving through the
trough should lead to cyclogenesis to the Lee of the Rockies late in
the period with the low tracking toward the mid MS Valley late in
the period with the boundary returning north as a warm front.

Unsettled weather should persist over the weekend, with a steadier
rain or showers on Saturday as the shortwave approaches and surface
low tracks to the south. Limited instability in the south could lead
to isolated thunderstorms, but most locations should receive a good
soaking rain from Saturday into Saturday evening. Shower chances
will linger into the day on Sunday and possibly even Sunday evening
mainly in the southeast as the upper low moves across the area.

High pressure will bring drier weather and clearing skies by late
Sunday night and persisting into Tuesday evening. With the shortwave
passing northwest at midweek and the cold front dropping toward the
OH Valley isolated convection will be possible on Tuesday night or
early on Wednesday in the far north. At the next system nears late
in the period, additional showers and thunderstorms will be
possible. However, higher chances are possible after the period.

High temperatures and average temperatures will be below normal over
the weekend. However, with more sunshine and high pressure in place
high temperatures should moderate to above normal levels by Tuesday
through Thursday. The pattern from early to the middle of next week
should support rather strong nocturnal inversions and valley low

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 751 PM EDT THU APR 20 2017

An approaching cold front will bring scattered to numerous showers
and thunderstorms to the area overnight into Friday from northwest
to southeast. VFR conditions will generally prevail through 06z,
and then ceilings will lower down to MVFR/IFR from northwest to
southeast as the boundary sags southeast into the area early
Friday morning. The front will linger across southeastern Kentucky
during the day on Friday, with additional convection firing up,
likely sustaining the MVFR ceilings. Some ceiling improvement
looks to take place from the north by Friday afternoon. Southwest
winds at 5 to 10 kts, with some gusts to around 15 kts, through
early this evening, will gradually shift to the west and northwest
through Friday.

&&

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

$$

UPDATE...GEOGERIAN
SHORT TERM...JMW
LONG TERM...JP
AVIATION...GEOGERIAN



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