Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 240900
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
400 AM EST Sat Feb 24 2018

.SHORT TERM...(Today through Sunday)
Issued at 400 AM EST SAT FEB 24 2018

The latest surface map features a stationary boundary aligned
southwest from eastern Kentucky down into the Arklatex region.
Aloft, troughing remains poised across the Rockies, with deep
southwest flow streaming in across the Mississippi Valley, and
ridging still hanging in across the western Atlantic. Showers have
been increasing in coverage overnight, thanks to a low level jet
moving into the Tennessee valley.

Widespread showers can be expected through Saturday morning, as
the jet continues to advect northeast into our area. Some of the
showers will be moderate to heavy, with generally around a half
inch of rainfall for most locations between what falls through
dawn and the rest of the morning. There may be even a few embedded
thunderstorms, with some locally higher amounts of rainfall.

The stationary boundary will lift back to our north as a warm
front by late this afternoon, allowing for a lull in convection,
especially across our southeast. Some thinning of the clouds is
also expected, so have gone a little warmer on the highs, with mid
70s likely. Temperatures elsewhere will range from the mid 60s
north of I-64, to the lower 70s south.

The relative lull in the convection will last into this evening,
before a stronger cold front moves in well after midnight. Some
stronger wind gusts will be possible with any storms that hang on,
but instability continues to look weak, and the best forcing looks
to remain just off to our west and northwest. Locally heavy
rainfall will be possible, but given the progressive nature of the
front, any hydro problems should be more isolated for most
locations.

Showers will exiting on Sunday in the morning as the front exits
off to the east, with a noticeably drier air mass working in
during the afternoon, as dew points fall into the 30s and 40s.
Highs will still be well above normal, with readings ranging from
the low to mid 60s.

.LONG TERM...(Sunday night through Friday)
Issued at 350 AM EST SAT FEB 24 2018

The period will begin with a surface high pressure building east
into the Ohio Valley. However, a 500mb shortwave and departing
300mb jet streak will help to develop a surface low to our south.
Some of the moisture and showers could move into the far southeast
and kept this idea stays close to the ECMWF. Overall this should
be light and we will see drying conditions in the afternoon hours,
as the surface high firmly sets up across the Ohio Valley. This
surface high pressure and some subtle 500mb riding will dominate
through Tuesday evening. Tuesday will be quite dry in the
afternoon, so did lower the dewpoints some especially in the east.

By midweek the models really struggle with the upper level
patterns which complicate the synoptic surface features. The
initial shower activity will be the result of warm sector 850mb
jet energy on Wednesday. After this a split flow pattern develops
in the 00Z ECMWF and the 00z GFS depicts coupling of the two
streams. This leads to varying solutions regarding the evolution
of surface lows, with much different timing from these two models.
The ECMWF has shown the most change this cycle given the two
different pieces of energy versus the more coupled system seen in
the previous run. Therefore could not see putting all the stock
into the latest ECMWF. However,I did lean on the model blended
POPs, but capped these at high likely given the varying solutions.
Also opted to lean toward the lower QPF presented by WPC as a
result of the varying solutions. The differing solutions will also
have implications on temperatures, with the GFS showing sounding
profiles that would support at least a mix of snow Thursday night.
That said, thought the model blend solution capping temperatures
in the 40s for lows at most locations on Friday morning was the
best approach. This will keep snow out of the forecast besides
Black Mountain until better agreement can be had by the various
model suites.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
ISSUED AT 145 AM EST SAT FEB 24 2018

A low level jet will bring widespread showers to the area through
Saturday morning. Have left out the mention of low level wind
shear, as it appears marginal between 09 and 13z. Expect
ceilings/visibilities to drop down to MVFR/IFR at times. Showers
will become more scattered in nature in the afternoon, as a warm
front lifts north of the area. Surface winds will be variable at
around 5 kts through Saturday morning, before becoming southwest
at around 10 kts, with gusts of 15 to 20 kts at times during the
afternoon and into the evening hours.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Sunday morning for KYZ044-050>052.

&&

$$

SHORT TERM...GEOGERIAN
LONG TERM...DJ
AVIATION...GEOGERIAN



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