Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 272043

Area Forecast Discussion
National Weather Service Jackson KY
443 PM EDT FRI MAY 27 2016

.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 18Z TAFS through 18Z Saturday afternoon)

All sites this early afternoon hour are remaining VFR with some
scattered CU across the eastern KY. We are seeing some isolated
showers developing along and near the VA border this afternoon and
this will become the aviation concern this afternoon. Right now
the issue is the isolated to scattered nature leads to VCTS
confidence at best. Most sites are not expected to get nearby
storms till generally after 20Z to 21Z. This could lead to brief
lowering in CIGS and VIS under heavier storms. Overnight the
concern becomes patchy valley fog and any location that gets
enhanced moisture from storms. Right now kept most sites VFR but
southern sites of SME/LOZ did add MVFR VIS. Given no steering flow
and high pressure no issues with winds are expected.


.JKL Watches/Warnings/Advisories...


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