Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 280600 AAA

Area Forecast Discussion...UPDATED
National Weather Service Jackson KY
200 AM EDT SAT MAY 28 2016

Issued at 130 AM EDT SAT MAY 28 2016

Did a quick update to fine tune the PoPs and sky cover through
the rest of the night. Also added in the latest shortblend
guidance to the T/Td grids and tweaked these for current obs and
trends. Finally, adjusted the patchy fog in the Wx grids through
sunrise. These updates have been sent to the NDFD and web servers.

UPDATE Issued at 1100 PM EDT FRI MAY 27 2016

Convection has died off across eastern Kentucky over the past
hour and have removed thunder for the rest of the night. Adjusted
temperatures a bit based on the latest trends in observations.
Southeast winds are currently keeping readings up into the mid 70s
in places, but the winds should gradually relent overnight,
allowing for most places to dip into the low and mid 60s, with
patchy dense fog seen.

UPDATE Issued at 751 PM EDT FRI MAY 27 2016

Scattered showers and thunderstorms continue to move in from the
south early this evening. Multiple outflows have been launched
out ahead of the current as well as earlier convection. The storms
will have a hard time making it further north in the east, as the
air has been tapped. As such, have a gradual weakening trend
through around 02z, with little in the way of activity expected
overnight given the weak forcing. The storms have been slower
moving at times, and locally heavy rainfall of one to one and a
half inches has fallen in places. Did hit the fog a bit harder as
a result, but some lingering cloud cover may keep it from
becoming too widespread.


.SHORT TERM...(This evening through Saturday night)
Issued at 349 PM EDT FRI MAY 27 2016

Afternoon showers and storms have developed as expected mainly
near the VA/TN border this afternoon. So far these showers have
struggled to become thunderstorms, and thus far little to no
lightning has been detected on the NLDN/ENTLN networks. That said
the MRMS VII product suggest only hints of ice in the far east
showers and that has been the area with the only cloud to cloud
strike so far. Either way will keep wx grids going with isolated
to scattered thunderstorms given the decent CAPE and steep lapse
rates. However given the fact that there is such weak steering
flow and no shear these storms will have a up hill battle becoming
organized. These showers and storms will be mostly diurnally
driven and are expected to subside through the evening hours.
After this did keep some valley fog in the forecast and this would
be enhanced in areas that do manage to see a storm.

For Saturday the focus shifts to the west where a 500mb wave
across the lower Mississippi River Valley that will eject NE into
western KY. This will bring PVA across western and central KY by
Saturday afternoon. This wave is also translating to the 700mb
level as well and will advect reasonable vertical velocities
across central KY. Right now will keep shower and storm chances
isolated to scattered through the day on Saturday with better
chances overall residing in the NW portions of the CWA. While the
weakly sheared environment and 700mb cap will be the caveat; steep
low level lapse rates, decent mid level dry layer, and MUCAPE
around 2000 to 2500 J/kg could be enough to get a isolated
marginally severe storm. The main risk would be gusty winds and
small hail

Saturday night we should see most of the storms subside as we
loose the heating. That said areas that see storms and deeper
valleys will have another opportunity to see patchy fog. After
this the GFS remains more robust with bringing weak PVA/western
wave influence and moisture from the potential tropical
disturbance. Meanwhile the NAM/ECMWF seem a bit more reserved with
this thought. Therefore toward dawn kept pops isolated coverage
and mainly in the far east

Temperatures in the short term remain above normal with highest
temps forecast in the far east.

.LONG TERM...(Sunday through Friday)
Issued at 400 PM EDT FRI MAY 27 2016

The period is expected to begin with a tropical disturbance along
the South Carolina or Southeast US coast with a ridge extending
west toward the Mid Atlantic from the Atlantic. Meanwhile a
shortwave trough is expected to be moving across the lower Ohio
Valley region at that point.

Early in the period, the tropical disturbance is expected to
meander a bit inland. The strength of the ridge to its north and
northeast determining how far west the disturbance gets and how
closely it approaches the area before being drawn north and then
northeast by the shortwave trough moving through the Ohio Valley
and Great Lakes region. This track would take the disturbance
toward the mid Atlantic and Northeast states from Sunday night
into Monday night. Model uncertainty remains in how close the
tropical disturbance would get to the region at the start of the
period and if it gets as far west as the 12Z GFS operational run
it might bring a bit better coverage of convection than is
currently forecast for Sunday into Sunday evening. At this point,
the main forcing on Sunday will be the approaching shortwave and
scattered coverage is expected at this time.

Rather weak ridging should move across the area from Monday night
into Tuesday night. The atmosphere though may not be completely
capped and convection may be able to break the cap over the
Cumberland Plateau or mountains near the VA border and or nearby
portions of East TN or SW VA and outflow into the VA and TN border
counties and lead to some isolated convection for Tuesday
afternoon and evening. Height rises are anticipated from Tuesday
night into Wednesday so Tuesday night should remain dry and
Wednesday could also possibly end up dry. However, models bring a
weak disturbance across the region and convection is progged by
both the GFS and ECMWF 12Z and prior runs.

A trough will approach the area from the west to end the period.
An associated cold front should then approach the area from the
west Wed night, with the front possibly crossing the area
by Friday. More organized convection is expected along and in
advance of the cold front. Convection will remain a possibility
through the end of the period as the 500 mb trough axis may not
cross the area before the end of the period.

High and low temperatures should average above normal through the
period, although highs on Friday might be near average depending
on the timing of the cold front. Overall, temperatures should not
be out of the ordinary for late May into early June.


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

Some MVFR fog will be possible through the rest of the night,
though mostly cloudy skies and light southeast winds should limit
it to just in the valleys and areas that saw heavier rainfall.
Any fog will burn off by around 12z, with a return of scattered
convection for Saturday afternoon. Light south to southeast winds
will gradually veer to the southwest through Saturday.


.JKL Watches/Warnings/Advisories...


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