Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 211722

National Weather Service Jackson KY
122 PM EDT Sat Oct 21 2017

Issued at 1111 AM EDT SAT OCT 21 2017

Now that fog has dissipated across the area, a forecast update has
been issued with fog removed. The rest of today will feature
light winds, mostly clear skies, and dry conditions. The latest
obs have been incorporated into the hourly forecast grids as well.

UPDATE Issued at 645 AM EDT SAT OCT 21 2017

Issued an update to the grids to input the latest observations and
trend them through the morning hours. Also slightly tweaked the
amount of fog in the grids as a bit more is present this morning.


.SHORT TERM...(Today through Sunday)
Issued at 331 AM EDT SAT OCT 21 2017

The main weather feature through the short term will be high
pressure anchored across the central Appalachian range. As this
high shifts east, southerly flow will be on the increase bringing
ample moisture northward into the region. This apparent even now
with upper level moisture in the form of cirrus drifting north
over central Kentucky. This will continue into the day today with
continued cirrus streaming north. Temps will be on the increase
with an increased southerly flow as well with highs reaching
around 80 for east Kentucky. This will likely fall a few degrees
short of the record of 83 for JKL and LOZ. Cloud cover will be on
increase into tonight along with increased winds as the next front
approaches from the west. This will lead to less fog development
tonight and slightly warmer low temps. The increased cloud cover
will lead to temps topping out around 80 again for highs on
Sunday. Overall, a dry short term forecast will be on tap as
precip should hold off from entering eastern Kentucky until Sunday
night. Therefore, the forecast challenge lies with the impact to
the highs and lows temperatures from the increased southerly flow.

.LONG TERM...(Sunday night through Friday)
Issued at 430 AM EDT SAT OCT 21 2017

Models are in good agreement through the bulk of the extended
portion of the forecast, with more significant differences showing
up in the latter 48 hours or so. The Canadian solution appears to
be the outlier, with slightly better agreement between the ECMWF
and GFS. While not great, the ECMWF has shown the best consistency
through the last couple of runs. Overall the pattern is amplified
and progressive. Digging, amplifying northern stream energy
appears to lift a southern stream storm system up and through the
Ohio Valley region early in the period. But significant
differences in details remain with strength and timing of short
wave energy tracking through the core flow of the eastern CONUS
trough. Bottom line is that some phasing of these two systems will
be possible which would influence the evolution and timing of
events through the first half of the extended. Mid and upper level
pattern then shifts rapidly during the last 72 hours of the
period as the eastern CONUS trough lifts out to the northeast in
response to energy carving out a deep trough across the western
CONUS. The ECMWF is a bit more amplified and slower with the
evolution of the pattern in general and digs the trough further
west. The GFS advertises a much broader trough that encompasses
just about the entire lower 48, which in turn brings storm systems
further east more rapidly with time.

For sensible weather a low pressure system will develop over the
Gulf of Mexico and move rapidly northward, through the deep south
and into the Commonwealth by Monday. This system will bring ample
moisture and produce a soaking rain for our area. At present much
of the area could see between an inch and an inch and a half of
rainfall from Monday through Tuesday. A strong cold frontal system
will sweep southward into the region late Monday night and through
eastern Kentucky by early Tuesday morning. Immediately after a
clipper like system will drop rapidly southeastward out of Canada
and through the upper Ohio Valley by late Wednesday. Combined
these three systems will usher in a breif shot of much colder air
for our area during the mid week time frame. Temperatures will be
low enough Thursday morning that frost will be a possibility,
especially in our more sheltered valley locations. Thereafter
temperatures moderate back up to normal levels through the
remainder of the forecast window.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)

The TAF sites should experience VFR conditions through out the
period, with light winds and dry conditions also expected. The
only cloud cover of note should be SCT to BKN high clouds that
will persist during the period as well. Any fog that forms late
tonight should be confined to valley floors and near bodies of




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