Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 260248 AAA

National Weather Service Jackson KY
948 PM EST Sun Feb 25 2018

Issued at 945 PM EST SUN FEB 25 2018

A boundary remains stalled out to the south of the area. A mid
level disturbance is expected to interact with the boundary with at
least one sfc wave of low pressure developing and moving along
the boundary. The deepest moisture and lift should remain south
of the area later tonight and into early on Monday. The models
still vary in how far north measurable light rain will reach, but
the consensus is that the highest chance for measurable
precipitation will be along the TN and VA border counties from
Whitley and Bell through Harlan and into Letcher. Locations
further north and west will be closer to surface high pressure
gradually building into the area and should not experience more
than mid level clouds.

Some slight adjustments have been made to pops prior to 6Z or 1
AM. The latest HRRR as well as 18Z and 0Z NAM as well as 12Z and
18Z GFS guidance and radar trends suggest that light rain should
not reach the KY/TN/VA tri state area until after 6Z. Measurable
pops have generally been held to along and south of KY Highway 80
with an area of possible sprinkles in a narrow stripe further
north. Likely pops from southeast Whitley County through Bell and
into Harlan County. Rainfall there should be light, generally a
tenth of an inch or less.


.SHORT TERM...(This evening through Monday night)
Issued at 240 PM EST SUN FEB 25 2018

19z sfc analysis shows just about all of eastern Kentucky now in
the wake of a departing cold front. This front is taking the lower
clouds east along with it as high pressure bubbles in from the
west. The relaxing of the pressure gradient from this high`s
approach has lightened the winds, though they are still cold
advecting - generally from the northwest. Temperatures currently
vary from the low 50s northwest to the upper 50s southeast while
dewpoints range from low 40s west to the lower 50s in the east.

The models are in good agreement aloft through the short term
portion of the forecast. They all depict broad southwest flow
continuing over the area between strong ridging above Florida and
troughing north of the Great Lakes down to the Southern Rockies.
The tail of the northern trough will weaken and head into the Ohio
Valley later tonight into Monday morning. From this, a weakening
batch of energy and slight height falls pass through eastern
Kentucky during the day Monday. Following this, ridging and gently
rising heights will move over the area into Tuesday morning.
Given the model similarities will favor a blended solution with
an emphasis on the details from the higher resolution NAM12 and
HRRR in the near term.

Sensible weather will feature mainly just high clouds around this
evening and overnight as high pressure builds into the area.
However, one last wave along the past frontal boundary will move
through the Southern Appalachians tonight brushing far
southeastern parts of the CWA with a decent chance of rain
showers. Otherwise, all will be quiet through eastern Kentucky
with relatively mild overnight lows on tap in the upper 30s north
to mid 40s south. Monday will be a nice day under high pressure
with plenty of sunshine and temperatures climbing into the mid to
upper 50s. As the high pressure area moves east Monday night, a
night of good radiation cooling will likely set up a moderately
large ridge to valley temperature split with the hilltops in the
mid 30s and most sheltered valleys falling into the upper 20s.
Also, look for valley fog to develop late at night and possibly
be thick near the rivers and larger bodies of water.

Used the CONSShort and ShortBlend as the starting point for all
the grids through Tuesday morning. Did make some significant
changes to the valley locations for lows on Tuesday and also some
point specific temps tonight and Monday. As for PoPs, limited the
measurable rainfall to just the far southeast tonight and only for
a window of time from 06 to 12z - narrower in areal and temporal
extent than the blends.

.LONG TERM...(Tuesday through Sunday)
Issued at 316 PM EST SUN FEB 25 2018

There is good model agreement with the evolution of the mean flow
during the upcoming week and fairly good agreement with the main
weather makers for our area.

With surface high pressure slipping to our east at the start of
the forecast period, and weak upper ridging over the area, we`ll
have a warm dry day on Tuesday. On Wednesday an upper level trough
will be moving out of the southwest U.S. as a surface low develops
in the southern plains. A leading short wave trough will bring
showers to the area on Wednesday. A more significant round of
showers will occur Wednesday night into Thursday as the southern
stream trough begins interacting with some northern stream energy
and develops into a closed upper low. The associated surface low
will deepen from Wednesday into Thursday as it moves into the
northern OH Valley-southern Great Lakes area.

There is model agreement that the axis of heaviest rains from
Wednesday into Thursday will fall south of Kentucky, but the
southern part of the forecast area could still see significant
rains, especially Wednesday night into Thursday. The current
forecast calls for 1.5 to 2 inches in the southern part of the
forecast area from Wednesday into Thursday, so this will need to
be watched. It is possible some local high water issues could
develop by Thursday.

Temperatures will be well above normal for the first part of the
forecast period, but colder air will spill into the area by Friday
with more normal temperatures for the start of next weekend.


.AVIATION...(For the 00Z TAFS through 00Z Monday evening)

VFR conditions will prevail through the period for all the TAF
sites. An increase in mid level clouds is expected from south to
north between 3Z and 9Z, though some MVFR cigs and possibly vis
is probable from 5Z to as late as 16Z or 17Z nearer to the VA and
TN borders as a surface wave passes through eastern Tennessee
tonight into early on Monday. Winds will generally be light and
variable through the period as high pressure gradually settles
over the area, especially after the surface low moves toward the
eastern seaboard.




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