Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 232306 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
706 PM EDT Sun Jul 23 2017

.UPDATE...
Issued at 706 PM EDT SUN JUL 23 2017

Freshened up the POPs through tonight based on the latest radar
and higher resolution model guidance trends. The best instability
gradient has been shifting slightly towards the Tennessee/Kentucky
border with time, with more sustained convection aligning from
north central Tennessee to southwest Tennessee. Scattered
convection has initiated across portions of the Cumberland Valley
in the last 15 minutes or so, and will continue to advertise the
highest POPs down in this area. Did tighten up the gradient of
POPs more so to the north, where the last few runs of the HRRR
has been suggesting more limited activity through this evening.
Updates will be out shortly.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 401 PM EDT SUN JUL 23 2017

MCV crossing east Kentucky into West Virginia has really zapped
our instability today. We really don`t see much CU out there.
There is a dewpoint/ouflow boundary draped across our far south,
near Middlesboro, where instability is much higher to the south of
this boundary. This would likely be the best area to see
development this evening as dewpoints have remained in the mid to
upper 60s back to the north. Temperatures have also remained a bit
cooler today to the north. All of this together has really
weakened the threat of storms for much of the area. With this in
mind, have opted to drop the flash flood watch for the northern
counties. Best rain chances will remain in the south closer to
that boundary this evening. Should see activity diminish quickly
by mid to late evening with dry weather expected overnight. With
more clearing expected tonight, we could see a good deal of
valley fog tonight. The cold front to the north will drop south
tomorrow afternoon/evening and may allow a few showers or storms
to pop up along the boundary at that time. Instability is rather
weak, but given the middle of the afternoon, can`t rule out an
isolated storm. As the cold front sinks to the south tomorrow
evening, dry weather will be seen through Monday night. We may see
another round of valley fog Monday night pending cloud cover.

.LONG TERM...(Tuesday through Sunday)
Issued at 440 PM EDT SUN JUL 23 2017

At the start of the period, a shortwave trough is expected to be
moving through the Northeast and Mid Atlantic states with an upper
level ridge centered over the Southern Plains region. Height rises
At the surface, a boundary should continue pushing south of the
area with high pressure expected to be centered across the Great
Lakes region and Ontario and building into the region. A period
of height rises should continue into the start of the period as
well.

Mid to upper level as well as surface high pressure centered
north or northeast of the area is expected to dominate through
midweek. The GFS is drier Tuesday into Wednesday compared to the
recent ECWMF runs though the 12Z ECMWF has trended drier. With
high pressure dominating, generally dry weather is expected for
Tuesday into Wednesday though the cap may be weaker near the VA
border and a slight chances right along the VA was used each
afternoon. Temperatures will be near to slightly above normal on
both days with with highs in the 80s on Tuesday and upper 80s to
near 90 on Wednesday. Lows will be a bit lower than recent nights
on Tuesday night in the mid 60s.

The high, however, should move east of the area by late Wed into
Wed night, with the boundary that will have stalled south of the
area lifting north as a warm front by late Wed and Wed night
and leading to increase in dewpoints and humidity.

Models continue to indicate a low pressure system moving across
central to eastern Canada during the middle to end of the week. An
associated cold front should drop south of the Great Lakes and to
the OH River on Thursday night. Models continue to indicate the
boundary should move south across the area on Friday in advance of
a shortwave trough. This boundary should continue to push south
of the area Friday night into Saturday. Once the axis of the
shortwave trough moves through on Saturday, height rises should
occur by the second half of next weekend, with high pressure
building toward the area.

With the approaching front and shortwave trough more organized
convection is expected from Thursday afternoon through Friday
evening. Until the shortwave trough axis moves south and east,
isolated convection cannot be ruled out over the weekend. Model
runs vary with timing this and this will ultimately determine if
next weekend ends on a dry note.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 141 PM EDT SUN JUL 23 2017

Dying MCS has really zapped the daytime warming thus far and thus
will keep thunderstorm chances at bay until after 20 or 21z. It
looks like there will be a narrow window this evening for a few
storms. Otherwise, mainly VFR conditions should dominate the TAF
period. If we can clear out late tonight, we could have to contend
with some valley fog, although no impacts are expected at the TAF
sites.

&&

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

$$

UPDATE...GEOGERIAN
SHORT TERM...KAS
LONG TERM...JP
AVIATION...KAS



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