Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 190546

National Weather Service Jackson KY
146 AM EDT Tue Sep 19 2017

Issued at 146 AM EDT TUE SEP 19 2017

Did a update to freshen up the short term grids. No significant
changes. GOES-16 showing another night of valley fog, but a bit
more mid level clouds moving in tonight, which could limit it a
bit more than the previous nights. We could still see some locally
dense fog however.

UPDATE Issued at 1045 PM EDT MON SEP 18 2017

Freshened up the near term grids to make sure they were on track
with the latest observations. Several locations in the far eastern
portion of the CWA have dropped near to or even below the
forecasted lows for overnight. This led to some adjustments in the
overnight lows and diurnal trends to better accommodate the
current trends. Also, the HWO and TAFs are giving dense fog
wording, but noticed it was not reflected in the grids. Went ahead
and added dense fog after 6Z, ranging from patchy to areas. All
changes have been published and sent to NDFD/web. A new forecast
package was sent out to reflect these changes and change to
overnight wording.

UPDATE Issued at 755 PM EDT MON SEP 18 2017

Forecast is on track so far this evening. Loaded in the latest
observations to make sure the near term grids were on track with
current conditions. Still a few isolated showers ongoing across
the far western portion of the CWA. Once these have tapered off,
will update the grids to remove the pre-first period rain
mention and sent out a new forecast package. All changes have been
published and sent to NDFD/web.


.SHORT TERM...(This evening through Tuesday night)
Issued at 435 PM EDT MON SEP 18 2017

20z sfc analysis shows weak high pressure in place over eastern
Kentucky though it is not effective in suppressing a few showers
now popping up over western parts of the Cumberland Valley. On
satellite, most of the area is seeing just small patches of cu,
but through the breadth of the Cumberland Valley, where the
showers are active, the clouds are more extensive and robust.
Plenty of sunshine for most of the area have sent temperatures up
into the lower 80s. Meanwhile, dewpoints are holding in the low
to mid 60s with the winds still light and variable.

The models are in fairly good agreement with the recent changes in
the mid and upper air patterns through the short term portion of
the forecast. They all now are a bit more hearty with the energy
that initially drifts through the weakening ridge this evening and
then even more so on Tuesday afternoon and evening. This latter
batch will lower heights and pool like a small trough between
periods of still rather weak ridging into Wednesday morning. Given
this agreement have favored a blended model solution along with a
good portion of specifics from the higher resolution HRRR and
NAM12 and a healthy dose of persistence - especially tonight and
early Tuesday morning.

Sensible weather will feature some widely scattered showers
through early evening - mainly over the western parts of the CWA.
a stray thunderstorm cannot be ruled out, as well. Otherwise, it
will be more of the same with clearing skies this evening and
cooling conditions leading to areas of fog - locally dense in the
river valleys for Tuesday morning. Look for the fog to dissipate a
bit quicker Tuesday morning as clouds move in from the west ahead
of a weak front. This will likely result in showers and
thunderstorms developing by early afternoon favoring the western
portion of the forecast area. The convection will die out in the
evening setting the stage for more fog development that night into
Wednesday morning - though limited by more clouds being around
through the night.

The CONSShort and ShortBlend were used as the starting point of
all the grids. Did make some adjustments to the temperature ones
each night based on terrain in anticipation of small to moderate
ridge/valley splits. As for PoPs, did tweak them for the diurnal
cycle peaking late afternoon and diminishing after sunset.

.LONG TERM...(Wednesday through Monday)
Issued at 306 PM EDT MON SEP 18 2017

An upper level ridge will amplify over the Ohio Valley through
the period continuing the unseasonably warm weather pattern for
our area. A weak upper trough trapped between Hurricane Jose and
the building ridge over the Mississippi Valley will cause the
potential for a few showers and storms Wednesday and Thursday.
That potential shifts to our southwest and withers as the upper
trough dissolves and surface high pressure builds southward
ensuring a dry weekend for our region.

Temperatures are expected to consistently top out in the low to
mid 80s each day through the period. Overnight lows are forecast
in the low 60s, then dropping into the upper 50s over the weekend
as drier air filters in.


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

Another complex night of valley fog and unlike the past few
nights, we do have some mid level clouds approaching the area and
could act to limit the fog density tonight. Dewpoints are also
running lower in the east and higher in the west than the past few
nights, so current thinking is the fog will be more suppressed
into the eastern valleys tonight, and perhaps a little more broad,
but not as dense in the west. This will still have potential to
impact the TAF sites with some reductions expected at KSME and
KLOZ. Fog will burn off a bit quicker in the morning with most fog
gone by 9 am. This will allow a return to VFR conditions. A few
widely isolated storms are possible Tuesday afternoon, but
confidence in the coverage is not high enough to include in the
TAFs at this time.




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