Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 201754
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
154 PM EDT Sun Aug 20 2017

.UPDATE...
Issued at 154 PM EDT SUN AUG 20 2017

Only minor changes needed to deal with the latest obs and trends.
Otherwise forecast remains on track.

UPDATE Issued at 1050 AM EDT SUN AUG 20 2017

Surface analysis indicates an area of high pressure to out north
across eastern PA and a weak stationary boundary to out north
nearer the Ohio River. The general surface high pressure and
rising heights will lead to another dry day across eastern KY. The
fog has now burned off for most based on Sat trends and therefore
have dropped the mention out of the text products. Otherwise only
minor changes needed for the latest obs and trends.

UPDATE Issued at 746 AM EDT SUN AUG 20 2017

Freshened up the hourly temperatures and dew points through
this morning, otherwise the forecast remains on track.

&&

.SHORT TERM...(Today through Monday)
Issued at 313 AM EDT SUN AUG 20 2017

The latest surface map features a weak quasi-stationary frontal
boundary located just north of the Ohio River, amidst high
pressure generally sprawled from the eastern Ohio Valley down
through the southern Appalachians. Aloft, a short wave trough is
pulling away across New England, with rising heights across the
lower and mid-Mississippi Valley.

Warming temperatures and mostly clear skies will be on tap across
eastern Kentucky through the short term, as an upper level
ridge builds in across the southeastern CONUS. Highs will average
in the upper 80s today, with lows in the mid to upper 60s tonight.
Expect some diurnally driven cumulus, but little in the way of
upper level clouds. For Monday, some thin cirrus will be
advecting in from the northwest during the day, and there will also
be a touch more afternoon cumulus, given the slight uptick in low
level moisture. Overall, this should not impede a good viewing of
the eclipse. Highs will be in the upper 80s once again, with a few
to several degree drop in temperatures during the peak of the
eclipse.

.LONG TERM...(Monday night through Saturday)
Issued at 323 AM EDT SUN AUG 20 2017

Strong upper level ridging in place will begin to break down Monday
night as a longwave trough pushes into the Ohio Valley. This trough
will remain in place, deepening, through the remainder of the work
week. Models are in good agreement of this troughing pattern through
this time, having it finally exiting east of the state during the
day Friday. Increasing heights are expected through the weekend,
though both the GFS and ECMWF are supporting generally WNW flow and
a couple of shortwaves passing eastward through the state as we head
into the weekend.

At the surface, still expecting a cold front to be located NE of the
region, in the Upper Mississippi Valley and Upper Great Lakes
Tuesday night. Meanwhile, surface high pressure will begin exiting
the state to the SE, allowing for return flow across the state ahead
of this approaching frontal boundary. The front is poised to make it
to the Ohio River during the late evening Tuesday, traversing the
CWA Tuesday night and into the day Wednesday, getting briefly hung
up along the high terrain, before exiting to our SE by Wednesday
afternoon. With the increased SW flow ahead of the system, shower
and thunderstorm chances are expected to begin plaguing the CWA
during the day Tuesday, increasing in coverage along the frontal
boundary Tuesday night into Wednesday morning. Once the front
passes, much more stable air will move in behind, quickly cutting
off any remaining thunder potential in the leftover precip. Have
only rain mentioned for late Wednesday afternoon and into Wednesday
night, though wouldn`t be surprised if dry air moves in quick enough
to cut off precip chances quicker than forecast.

For the remainder of the work week, surface high pressure will be in
place. The upper level troughing in place will promote NW flow
across the region, helping to keep temperatures at bay (below
seasonal normals). Highs Wednesday will be in the upper 70s, with
upper 70s to around 80 expected through the end of the forecast
period. Northerly winds will also promote less humidity, making for
pleasant conditions into the weekend. Despite the strong high
pressure in place, the above mentioned shortwaves that may pass over
the region during the weekend could lead to a stray diurnally driven
shower or thunderstorm. The best chance for this will be Sunday as
the high starts to drift to our NE and more southerly flow makes it
back into the region.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 146 PM EDT SUN AUG 20 2017

Surface analysis shows an area of high pressure parked across SW
PA and a warm front lifting north across the Ohio Valley. We will
remain under the influence of the surface high pressure and
rising heights. This will lead to a typical summer like pattern
across eastern KY, with a few higher clouds and a few low level
CU at about 5 kft. The CU will dissipate this evening and mostly
clear skies will prevail. This will be the catalyst for fog
development once again tonight. Given the conditions last night
will lean toward low MVFR VIS toward 06Z at SME/LOZ/SYM. This fog
is expected to lift and burn off by around 13Z or so Monday
morning. We could see some afternoon CU again Monday around 5
kft, but uncertain on how coverage will be affected by solar
eclipse across eastern KY. Winds will remain light for the period.

&&

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

$$

UPDATE...DJ
SHORT TERM...GEOGERIAN
LONG TERM...JMW
AVIATION...DJ


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