Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 261744

National Weather Service Jackson KY
144 PM EDT Thu Apr 26 2018

Issued at 1100 AM EDT THU APR 26 2018

Low pressure over northern MS this morning will move east today,
before turning northeast this evening. Rain currently over TN will
be slow to advance north today, but will pivot north across the
southeast part of the forecast area by late afternoon or evening
as the low pressure system moves east and begins it northeast
turn. Have updated the forecast with latest observational trends
and short term guidance. Main change is to slightly slow the
northward advance of rain chances this afternoon.

UPDATE Issued at 755 AM EDT THU APR 26 2018

Fog and low clouds were affecting much of the area early this
morning, but will dissipate during the morning. However, higher
clouds associated with the next weather system will be on the way
in and probably keep sunshine limited today. Otherwise, early
morning temperatures have been blended into the forecast, with no
real impact.


.SHORT TERM...(Today through Friday)
Issued at 419 AM EDT THU APR 26 2018

The low pressure system which brought rain to the area over the
last few days has finally departed to the northeast. There is no
appreciable change in air mass in its wake, and with clouds trying
to break up at times, the cooling of the already damp surface air
has led to fog development in many areas. The fog should dissipate
on Thursday morning as temperatures start to climb. However,
clouds with the next weather system will be on the way in, and
only allow for very limited sunshine.

Early this morning, this next low pressure system was centered
over AR and northern MS. It will track eastward, passing to our
south late today and this evening. Models have settled on a
solution bringing light rain to our southern and southeastern
counties, with more significant rain further to the south and
east. Have continued with a 60-70% POP near the TN and VA borders,
tapering to less than 20% north of I-64. This system turns
northeast on the east side of the Appalachians as it pulls away

Most of the forecast area can then expect a dry day on Friday.
With no appreciable change in air mass, and clouds breaking up,
temperatures should be milder. A cold front will approach from the
northwest late in the day. Moisture will be very limited along the
front, and the prospect for precip is small. The GFS does have
some showers developing in shallow convection in our northwest
counties toward evening, but the NAM and ECMWF keep precip to our
north. In a compromise, have used just a 20% POP north of I-64
late in the day.

.LONG TERM...(Friday night through Wednesday)
Issued at 419 AM EDT THU APR 26 2018

Large scale troughing will be in place across the Ohio Valley to
start off the period Friday night into Saturday, deepening as a
closed low develops and rotates through the Great Lakes region. This
low is expected to exit east of the Great Lakes by Sunday
evening/night, with rising heights taking hold across Kentucky as
upper level ridging begins to move into place. This ridging will
encompass much of the eastern Conus by Tuesday. Both the ECMWF and
GFS are in good agreement about large scale troughing across the
western half of the Conus during this time, with a upper level low
developing within the trough axis and quickly rotating SE,
drastically lowering heights across the western most states. As this
closed low makes the shift northeastward towards the Central Plains
during the day Wednesday, heights across the central U.S. will lower
quickly. The closed low will eventually weaken and become absorbed
into the trough again, but not before heights begin lowering across
Kentucky during the day Thursday.

As for sensible weather, an area of precipitation will be associated
with a surface low pressure system moving through the Great Lakes
Friday night and Saturday. While there is still some uncertainty on
the exact expanse and track of this precipitation swath, the ECMWF,
NAM80, and ECMWF show the main area of precip north of the Ohio
River, expanding into far SE KY during Saturday afternoon under more
W to NW flow. As such, kept mention of pops out of CWA Friday night
through the first part of the day Saturday, with just slight chance
pops for Saturday afternoon.

After this system moves out, an expansive area of surface high
pressure will take hold across the region for the remainder of the
weekend and well into mid week next week. Each day that ridging and
high pressure are in place means the airmass will modify warmer,
especially as southerly winds set in. Highs on Sunday will be around
60 degrees under NW flow...however by Monday sunny conditions
combined with a more Srly flow will boost afternoon temps into the
low 70s in many locations. In fact, current forecast has
temperatures possibly reaching 80 degrees by Tuesday in a few
locations. The same will be true for Wednesday as well.

By late Wednesday afternoon and into Thursday, clouds will be on the
increase as a cold front begins to near the region from the west,
following the greatest height falls aloft. Despite clouds, the
strong Srly flow will still boost temps to near 80 for highs on
Thursday. A few pop up showers will be possible as early as
Wednesday afternoon ahead of this system, so kept in the slight
chance pops that the Superblend gave over portions of the western
CWA during this time. These will quickly diminish in the evening.
The main line of precip associated with this storm system will then
begin impacting western Kentucky during the day Thursday. This will
result in generally slight chance pops across our western CWA
throughout the day, increasing just past the forecast period as the
system continues on its eastward track towards JKL.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)

VFR conditions will prevail across the entire area at the start
of the forecast period, with MVFR to IFR conditions developing
tonight across the southern and eastern part of the area. Low
pressure over northern AL early this afternoon will drift east
before turning more to the northeast tonight. As the low pulls
northeast light rain will spread into the southern and eastern
part of the forecast area this evening. Ceilings will lower in the
south and east tonight with visibility decreasing in light rain
and fog. The lowest ceilings and visibility are expected in the
far southeast and far east. VFR conditions will persist the entire
forecast period in the far north and northwest part of the
forecast area. Conditions will improve Friday morning, with VFR
expected across the entire area by mid to late morning. Winds will
remain light from this afternoon into Friday afternoon.




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