Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 200537

National Weather Service Jackson KY
137 AM EDT Thu Oct 20 2016

Issued at 137 AM EDT THU OCT 20 2016

OBS and SAT indicating high clouds streaming across the Bluegrass
and a mid level deck progressing into the Lake Cumberland region.
The high clouds are associated with activity near the Ohio River
and frontal boundary. The mid level clouds streaming into the
south are from a LLJ and mid level wave. Overall did slow POPs
down in both the north and south through the pre dawn hours. This
as the frontal boundary to the north is making little progress
south this hour, and activity to the south is progressing into the
region slower. Overall seemed like the short term model blend had
a good handle and blended toward this product. Otherwise more
minor adjustments were need for the latest obs.

UPDATE Issued at 1040 PM EDT WED OCT 19 2016

The forecast has been on track all evening. A few small rain
showers moved across a couple of hour northern counties earlier
this evening, but not much has been going up there over the past
few hours. We are still expecting isolated to scattered showers to
begin moving into the area around dawn tomorrow. Cloud cover will
gradually increase overnight from the west and northwest as a
frontal boundary approaches. Recent obs were ingested into the
hourly forecast grids to establish some new trends. Aside from
that, no major changes to the forecast were needed.

UPDATE Issued at 742 PM EDT WED OCT 19 2016

The forecast remains on track so far this evening. Showers and
thunderstorms were ongoing north of the Ohio River this evening,
but little if any precipitation has made into eastern Kentucky as
of yet. A few showers and storms are still expected to move across
the I-64 corridor this evening. Scattered showers are still
expected to move into the area from the west and southwest late
tonight. Skies are still generally partly across the area, with
both low and high level clouds moving across the area.
Temperatures, winds, and humidity were all still on track based on
the most recent observations. These obs were ingested into the
forecast grids to establish new trends. Aside from that, no other
changes to the forecast were deemed necessary at this time.


.SHORT TERM...(This evening through Thursday night)
Issued at 357 PM EDT WED OCT 19 2016

Surface map shows a stationary boundary just to our north along
the Ohio River. High resolution models suggest this boundary will
lift slightly northward tonight in response to a sfc wave of low
pressure as it continues to develop over the Ozarks. This feature
will move rapidly northeast overnight along the Ohio River Valley.
This low should be between SDF and CVG by dawn Thursday and will
pull a cold frontal boundary through our area as it continues to
track up the Ohio Valley. The sfc front should be completely
through our area by sometime Thursday evening.

This system will bring our first opportunity for a substantial
widespread rainfall in quite awhile. ATTM a blend of model and
guidance QPF totals suggests between 0.75 and 1.25 inches of
total rainfall will be possible with this storm system, some much
needed rainfall should that come to fruition. Behind the front
temperatures will take a slow but steady drive southward as much
cooler air filters into the area late Thursday and Thursday night.

Best chance of thunder will come during the day Thursday. SPC has
our area in a Marginal Risk for severe weather. There is sufficient
surface based instability and fairly strong 0-6 km shear, so can
not rule out that possibility. However at this time forecast
soundings suggest CAPEs will be relatively low. If soundings are
correct, this will tend to counteract the potential for severe
weather. And other sounding parameters are generally unimpressive.
For now will keep current HWO wording suggesting only a few strong

.LONG TERM...(Friday through Wednesday)
Issued at 357 PM EDT WED OCT 19 2016

There is good model agreement that at 12Z Friday the cold front will
be well southeast of the area, with the axis of the mid level trough
poised to move across the area during the day. Any lingering
showers will be diminishing on Friday as the trough passes to our
east. The standard model blend keeps a slight chance of showers
in the far east into Friday evening, but after that there will be no
mention of precipitation chances for the remainder of the forecast

There is also good model agreement, including the GFS ensemble, that
850 mb temperatures will plunge to -1 to -2 C by 12z Saturday. At
this time there is still some doubt about how much clearing will
occur Friday night. Even with the sub freezing 850 mb temperatures
Saturday morning clouds would keep temperatures warmer than might
otherwise be expected. Will follow the standard blend and
keep minimum temperatures around 40 degrees for most areas Saturday
morning. While 850 mb temperatures will warm by 5 or more degrees by
Sunday morning, it is likely that some valleys will have colder
temperatures Sunday morning than Saturday morning, with generally
clear skies expected by then and good radiational cooling
conditions from Saturday night into Sunday morning. Will not mention
frost at this time for Saturday or Sunday morning, but this
possibility will need to be monitored for later forecasts.


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

VFR conditions are the story for the beginning of the period, but
we will see decreasing VIS and Lowering CIGs late in the period.
Cold front remains north of the region this hour and this will be
the story through the night. There is a mid level wave and 850 mb
jet that could induce a few showers toward dawn, and these
showers are showing up on radar down in portions of TN this hour.
However kept the POPs in the slight range at this point and
generally do not introduce VCSH till 12z to 14z. By Thursday
afternoon we will see chances for rain on the increase and the
potential for Thunderstorms. A few of these storms could be strong
and lead to gusty winds. Generally TAF sites will see fluctuations
from MVFR to LIFR depending on the strength of the storms that
happen to hit a site. Overall the first part of the period winds
will remain light, but increased wind gusts are possible through
the afternoon.




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