Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 210850

National Weather Service Jackson KY
350 AM EST Wed Feb 21 2018

.SHORT TERM...(Today through Thursday)
Issued at 350 AM EST WED FEB 21 2018

08z sfc analysis shows a well defined front off to the northwest
of the area and just now entering western parts of the state.
Ahead of this, incredibly warm air is in place over eastern
Kentucky this night with readings far more typical of summer.
southwest winds of 5 to 10 mph with occasional higher gusts have
been supporting these elevated temperatures for much of the area.
Even so, there have been enough thin spots and clear patches in
the clouds overnight so that an inversion set up and many of the
far eastern valleys were able to radiate down into the 50s.
Currently readings vary from the upper 60s to near 70 on the
ridges and more open areas to the mid 50s in those most sheltered
valleys. Dewpoints are more uniform in the mid to upper 50s.
Again, fog appears to be non-existent across the area given the
warm temperatures.

The models are in excellent agreement aloft through the short
term portion of the forecast. They all hold an anomalous ridge
just off the Southeast Coast with its influence felt deep into the
Appalachians. Lower heights and troughing will pass by well to the
north tonight into Thursday as deep layer southwest flow
persists. This trough will encourage a few stronger mid level
impulses to pass through northern Kentucky late tonight and into
Thursday morning before the flow aloft settles with time that
afternoon. Given the good model agreement will favor a general
blend with a strong lean on the higher resolution HRRR and NAM12
for details.

Sensible weather will feature very warm conditions continuing
through the southeast parts of the area as the front slowly
settles into the northwest portion of the JKL CWA. Indications
are that this boundary will weaken as it stalls with sfc
convergence flagging before it gets too deep into our area this
afternoon - likely keeping the heaviest rains off to the north and
west through evening. Very mild conditions continue tonight for
most locations. Another surge of moisture and lift will then
spread northeast along this boundary in association with the
compact mid level shortwaves and better 300mb divergence passing
by overnight. This surge will bring another round of showers and
potential thunderstorms to the area into Thursday morning with the
northwest favored for the heavier rains. After a brief lull in
its immediate wake the boundary will then remain active into the
afternoon Thursday with another sfc wave developing and running
east northeast into eastern Kentucky. This latter wave will bring
with it PW air in excess of 1.5 inches - or 200 to 300 percent
above normal. Will target this wave for heavy precipitation
potential and also address this particular anomaly in a
forthcoming ESF product in lieu of any flood watch at this time.
Do believe that flood watches will eventually be needed for the
weekend rounds of rain as this current batch will likely leave
the area near saturation - especially outside of far southeast
Kentucky. Will maintain the small chance for thunder today and
continue that tonight and through Thursday for at least the
southeast parts of the CWA where sfc based instability will be

Used the CONSShort and ShortBlend to kick start the grids with
only minor temperature adjustments through the short term -
outside of this morning`s eastern ridge/valley differences. As for
PoPs: have upped them for today as it seems the blend was
weakening the front too quickly - though somewhat lighter QPF is
now expected for our area today.

.LONG TERM...(Thursday night through Tuesday)
Issued at 245 AM EST WED FEB 21 2018

The first half of the extended period will feature continued well
above normal temperatures and multiple rounds of rainfall. The
rainfall could be moderate to heavy at times, especially Saturday
and Saturday night. A series of weak areas of low pressure moving
along a stalled frontal boundary will be the impetus for the rain.
The rain will taper off and finally come to an end on Sunday, as a
large area of low pressure aloft finally dislodges the surface front.
After that, we can expect a few days of mostly dry weather, as a
ridge of high pressure builds across the region. Another bout of
rain may occur at the very end of the period, but this is very
uncertain at this time.

Temperatures during the first 4 days of the extended will be the
warmest of the period, with highs on Friday topping out in the 70s,
the 60s and 70s on Saturday, the 60s on Sunday. A cool down will be
on tap for the end of the period, with daily highs maxing out from
the mid 50s to lower 60s on Monday and Tuesday. Nightly lows will
generally be in the 50s Thursday night, Friday night, and Saturday
night. After that we will see lows in the upper 30s and lower 40s.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)

The TAFs will remain VFR through the night, before lower CIGs
advect southeast later this morning and into the afternoon. Right
now will keep this MVFR for most sites during the day, but
following sunset, expect lower cigs to develop for all the sites
from northwest to southeast. A stalling front dropping into the
area from the northwest will bring showers into the forecast area
starting later this morning and continuing into the afternoon.
This could also lead to brief lowering of CIGs and VIS in heavier
showers or a stray thunderstorm - kept VCTS out of the TAFs for
now owing to limited instability. The winds will also gust 15 to
20 knots ahead of the boundary. Before then, though, LLWS will
again plague the area with winds off the sfc at 40 to 45 kts from
the south southwest through 14z or so.




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