Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 211820 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
120 PM EST Tue Feb 21 2017

.UPDATE...
Issued at 100 PM EST TUE FEB 21 2017

High clouds have so far been thin enough that plenty of sunshine
came through and spiked temperatures into the 70s for much of the
area. Have updated to take them up into the low and mid 70s across
the CWA. Record temperatures have been exceeded here at JKL - 72
and are nearly so at LOZ - 70. Some light returns - likely not
reaching the ground are starting to show up on radar - have added
sprinkles into the wx grids for these through the rest of the
afternoon. These updated grids have been sent to the NDFD and web
servers.

UPDATE Issued at 1030 AM EST TUE FEB 21 2017

15z sfc analysis shows a developing area of low pressure rolling
through the lower Mississippi Valley. Pcpn from this is trying to
work toward eastern Kentucky but making very little progress. Dry
air initially - dewpoints generally in the upper 30s to lower 40s
- will slow the arrival further. Even the clouds are not too thick
over most of the area with some sun patches leading to
temperatures back up in the low to mid 60s already for most places
- though a few mid and upper 50s are found in the eastern Valleys.
For this reason, have raised highs a notch as well as adjusted
sky cover a bit lower into the early afternoon. Winds will
increase from the south at 5 to 10 mph with gusts up to 15 and 20
mph by mid afternoon. These updated grids have been sent to the
NDFD and web servers.

UPDATE Issued at 649 AM EST TUE FEB 21 2017

Rain still well off to the west across western Indiana and western
Kentucky. Before showers arrive late this afternoon, expect cirrus
to gradually lower as abnormally warm temperatures occur once
again.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 401 AM EST TUE FEB 21 2017

Abundant cirrus will continue to stream in from the Gulf of Mexico
downstream of a narrow upper trough stretching from the Northwest
Territories into Mexico. The northern portion of this feature,
extending through the Ohio into the Tennessee Valley, will dampen
and shear out through the day as the southern stream cuts off across
the lower Mississippi Valley and Gulf of Mexico. South to southeast
surface winds will remain in place as surface ridging moves off the
Atlantic coast with low pressure following a similar course to that
of the southern U.S. upper low. Height falls coupled with arrival
of decaying energy aloft will lead to developing rain shower
chances by late this afternoon across eastern Kentucky. The lack
of any notable surface features nearby, due to a decaying cool
front in the Ohio Valley associated with a low moving through
Ontario, raises some question as to the extent of precipitation
development. Additionally, a downsloping component to the low
level flow raises uncertainty as to how much rain will fall,
especially across southeastern Kentucky nearer the higher terrain.
Nonetheless, the presence of energy aloft in tandem with a moist
warm sector airmass spells showers becoming scattered to numerous
through the evening and tonight. Deeper mixing today, owing to
the recent subsidence inversion lifting, should allow for similar
temperatures despite a relatively cooler pocket of 850 mb
temperatures to tap into. Highs look to top out in the upper 60s
to near 70 degrees.

Far southeastern Kentucky will stand a better chance for
widespread rainfall as the southern stream cutoff low pushes
east/southeast into the northern Gulf later tonight into early
Wednesday. Precipitation amounts may again be cut into with weak
downslope flow in place, but the probability of measurable
precipitation is certainly high.

Weak shortwave upper ridging will follow departure of the weakening
trough Wednesday, but it will not take much forcing to kick off a
few showers through the day given the degree of moisture in place.
Showers lingering from the morning will also be slow to exit east of
the Commonwealth as westerly steering flow weakens into the
afternoon. Although still well above normal, high temperatures
should cool off a tad from Tuesday with readings in the mid 60s.

.LONG TERM...(Wednesday night through Monday)
Issued at 401 AM EST TUE FEB 21 2017

Extended period features potential for record high temperatures,
then turning much cooler but remaining near normal.

The period begins with a weak upper level and surface feature that
introduces a chance of showers for Thursday morning into Thursday
afternoon. These features here are quite subtle and therefore
think the chance POPs seem robust enough at this point. Overall
think the NAM seems most overdone QPF wise, but this will depend
on any convection that could develop. Based on the instability the
best chances for storms would be across the Bluegrass, but only
went slight at this point given the cloud cover and before
mentioned very subtle features. Then all eyes turn toward a upper
level trough and surface low developing across the Northern Plains
Thursday night. First thing this will do is bring warm southerly
flow and temperatures will soar into the low to mid 70s for all on
Friday. This system will deepen as the upper level closed low
takes on a negative tilt and ejects the surface low into the Great
Lakes by Friday afternoon and evening.

The feature we will be watching is the trailing cold front
combined with height falls that will bring a good shot of showers
and thunderstorms to the region. Given the dynamics of this system
with strong shear and decent CAPE we could see a isolated strong
storm Friday evening. Overall based on the upper level dynamics
would think the better chances for stronger storms would be west
of the CWA across Western KY and into portions of the Midwest.
This front will cross the region overnight Friday into early
Saturday morning ushering in much cooler air compared to what we
have become accustom. These near normal temperatures will remain
the story for the remainder of the long term period. The model
guidance becomes more divergent with the GFS wanting to bring a
clipper type system through, but little support is rendered from
the ensemble mean of the GFS or other long term synoptic guidance.
Therefore stuck with the slight to chance POPs for Sunday night
into early Monday. Some of this could be more in the way of snow
Sunday night into Monday morning, but given low confidence not
going to put this in HWO at this point.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
ISSUED AT 120 PM EST TUE FEB 21 2017

VFR conditions will continue through this afternoon and much of
the evening. Cloud bases will lower through the evening, though,
with MVFR (and possibly down to IFR in the rain) ceilings
materializing later tonight. Rain showers will increase in
coverage late this evening and overnight before tapering off from
northwest to southeast Wednesday morning. Winds will be
occasionally gusty to 15 kts this afternoon before we solidly
cloud over then speeds will settle to between 5 and 10 kts
generally from the south - becoming light and variable tonight
through Wednesday afternoon.

&&

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

$$

UPDATE...GREIF
SHORT TERM...GUSEMAN
LONG TERM...DJ
AVIATION...GREIF



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