Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 250829
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
429 AM EDT Wed Apr 25 2018

.SHORT TERM...(Today through Thursday)
Issued at 416 AM EDT WED APR 25 2018

The deep 500mb low that has been sitting across Kentucky is finally
on its eastward exit this morning. It will shift northeast from the
Carolinas to Virginia today, as it becomes absorbed within longwave
troughing from another upper level low located over the Great Lakes.
Heights will flatten a bit across Kentucky during the day, however
this will be short lived as another upper level low deepens across
the Central and Southern Plains during the day, shifting southeast
into the lower Mississippi Valley tonight and across the Deep South
during the day Thursday.

At the surface, low pressure associated with the current exiting
upper low will also continue to shift east of the region through the
day , as it rides up the mid Atlantic coast. This will result in
continued NW flow across the state throughout the day, including in
the mid and upper levels. Furthermore, a weak cold front is expected
to shift eastward across Kentucky during the day, connected to both
a surface low pressure system over the Great Lakes region, and
another low moving across the mid-Mississippi Valley, associated
with the above-mentioned incoming upper level system. While the
frontal system itself will have little impact, the deep N to NW flow
across the region will be enough to pull moisture from the Great
Lakes region southward into Kentucky. This will result in continued
clouds across the region, and also promote isolated to scattered
rain showers, especially in areas where upslope flow is favored.

The front should exit SE of the region overnight, with weaker flow
and high pressure taking hold in its wake, effectively cutting off
any remaining precip chances for the night. Could see some patchy
fog development, though forecast soundings are still supporting low
clouds lingering across the region.

As we head into Thursday, high pressure will remain in control for
much of the CWA throughout the first half of the day. However as the
low pressure system to our south traverses eastward across the
Tennessee Valley towards the Appalachians, moisture from this system
will begin to push northward into Kentucky. As such, expect yet
another day of cloudy skies. Scattered rain showers will be possible
across the far southern CWA throughout Thursday morning, expanding
north and eastward during the second half of the day as the center
of the low draws closer to the region.

As for temperatures, the ongoing cloud cover expected throughout the
short term portion of the forecast will keep temperatures fairly
uniform across the CWA, and mild overnight. Deeper NW flow today
will keep temperatures around 60 degrees for highs. Overnight lows
will fall into the upper 40s across the region. Weaker flow (less
northerly wind influence) will be enough to boost temps a few more
degrees for Thursday, with highs in the low to mid 60s.

.LONG TERM...(Thursday night through Tuesday)
Issued at 429 AM EDT WED APR 25 2018

A weak low pressure system will be passing by to our south as the
period starts. Models have come into better agreement on this
system compared to yesterday. The ECMWF trended toward the
American models for a track further to the north, bringing rain to
the JKL forecast area Thursday evening. In light of this, a
likely POP is being used in southeast Kentucky, with a 20% POP
extending all the way to the northwestern edge of the area. This
system will depart to the east overnight.

No meaningful change in air mass will occur with the system, but
following it, there are a couple of cold fronts expected. One
should pass on Friday, and the other on Saturday. They will be
weak and will have very little moisture present when they pass.
Their main effect will be to hold temperatures in check in the
face of strong spring sunshine. The cold frontal passages will be
enabled by an upper trough over the northeast CONUS. This trough
will depart to the east late in the weekend, and an upper level
ridge is expected to become established over the southeast CONUS
for the early part of the week. Coupled with a return of warm air
advection, this will send our temperatures well into the 70s or
near 80.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
ISSUED AT 159 AM EDT WED APR 25 2018

A large and stacked weather system over the TN and OH valleys
continues to rotate to the east, at present centered southeast of
the state. Showers associated with this system have diminished
throughout the evening resulting in the removal of VCSH from
overnight portion of the TAF, though did keep VCSH mention for
during the day Wednesday at most sites as activity is likely to
ramp back up with daytime heating. Despite the current lack of
rainfall, flight conditions are still expected to generally
deteriorate through the overnight as the upper system slips over
the area. The poor aviation categories will be mainly from the
CIGS as they drop into IFR/LIFR territory, and even below airport
minimums at many of the TAF sites. Expect these conditions to
persist through at least the first half of the day Wednesday, with
slowly improving conditions expected for the afternoon and
evening. Most sites should see the return of MVFR CIGS by evening,
continuing into the overnight. Winds will be light and variable
throughout the period, with any predominate winds generally out of
the NW 5kts or less.

&&

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

$$

SHORT TERM...JMW
LONG TERM...HAL
AVIATION...JMW



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