Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 301533 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1133 AM EDT Fri Sep 30 2016

.UPDATE...
Issued at 1135 AM EDT FRI SEP 30 2016

14z sfc analysis shows the reflection of the stacked low just to
the west and north of eastern Kentucky. This slow moving system is
responsible for the clouds today along with the some sprinkles
for the majority of the CWA and better shower chances in our
western and eastern fringes. Just to the north of the forecast
area thunderstorms will be possible with the stronger ones likely
contained to places closer to the Ohio River. Areas of dense fog,
mainly affecting the ridges, will continue to break up over the
next hour or so. However, the fog and clouds have managed to slow
the diurnal rise through eastern Kentucky area with readings not
far from the low to mid 50s. Once the low clouds and fog lift
temperatures should be able to rebound toward forecast highs this
afternoon. Meanwhile, dewpoints are in the low to mid 50s across
the area with light and variable winds. Have updated the Sky,
PoPs, and Wx grids along with T and Td ones for the latest obs and
trends. These have been sent to the NDFD and web servers. An
updated ZFP was also sent - mainly to remove the fog wording.

UPDATE Issued at 750 AM EDT FRI SEP 30 2016

Patchy dense fog continues across portions of eastern Kentucky
with low stratus plaguing the region. Will see this fog mix out
and stratus begin to lift with sunrise and subsequent turbulent
mixing.

&&

.SHORT TERM...(Today through Saturday)
Issued at 357 AM EDT FRI SEP 30 2016

The well advertised upper low continues to spin over Lexington this
morning, bringing isolated shower activity to far eastern Kentucky
toward the Ohio Valley. Dry slotting has wrapped into much of the
rest of eastern Kentucky on the northwestern flank of a surface low
positioned across western North Carolina. Will continue to see the
main precipitation shield move northward through the day today as
the upper low slowly wobbles toward the Ohio River, thus keeping
much of eastern Kentucky dry. For those areas in the Bluegrass
region and near the West Virginia border who do see rain today,
capping aloft should negate any chances for thunder with cloud tops
struggling to punch above 10k feet. Nonetheless, will still hang on
to a good deal of cloud cover through the day under the presence of
cyclonic flow. A meager intrusion of warmer air aloft as the low
meanders northwestward will help warm temperatures a few degrees
from Thursday`s readings, with highs topping out in the mid-upper
60s.

The Bluegrass region through portions of the Interstate 75 corridor
will see a slight bump in precipitation chances this evening into
tonight as an upper impulse looks to round the southern periphery of
the parent upper low. This will help to reintroduce cloud cover from
west to east as warm air advection ensues aloft. Overnight lows
still look to drop into the mid-upper 40s in valleys and low 50s on
ridges as this warmer air will be confined to above the nocturnal
boundary layer.

Will begin to tap into some of this warmer air aloft Saturday
morning as turbulent mixing occurs with deep layer southwest flow
remaining in place. This will send temperatures back to near normal
values, with highs in the upper 60s to mid 70s. Shower chances will
be greatest in the Bluegrass region nearer the best pool of moisture
and forcing for ascent. Will again see decent low level lapse rates,
but quicker warming aloft near the 700 mb level will promote strong
enough capping again to keep any mention of thunder out of the
forecast.

.LONG TERM...(Saturday night through Thursday)
Issued at 415 AM EDT FRI SEP 30 2016

The strong closed low that has been rotating over top of KY during
the short term will finally begin to shift to the NE, reaching
northern IN and OH by 0z Sunday. The low will become less wrapped up
as it continues into the lower Great Lakes by 0z Monday, allowing
weakening gradients of isobars aloft. Upper level ridging will begin
working in to start off the workweek and should remain in place
through midweek. Meanwhile, a strong upper level low in place across
northern CA and Washington Monday will continue its path westward,
with deep troughing resulting across much of the western conus. The
ECMWF and GFS agree quite well on the general pattern, however are
struggling just a bit with placement and strength through Wednesday.
However, by Thursday both models come back into better agreement as
the low continues to move northeast and into MN/ND/south-central
Canadian border. The associated trough is expected to start pushing
into Kentucky during the day Thursday and continue through the end
of the forecast period.

Also during this time period, models are continuing to come into
better agreement about the tropical system in the Atlantic
approaching the southeast coastal states and then riding up along
the east coast by next weekend. Overall, at this point, it does not
look to affect our weather here in KY during the forecast period.

With the exiting upper level wave in place, the associated surface
low will also begin exiting to the north. This will leave high
pressure in place across the region with winds shifting from SW to N
from 0z Sunday through 0z Monday. Some slight chance rain showers
will still be possible to start the period before the system fully
exits far enough north. But by Sunday evening, high pressure will be
fully in control with northerly winds preventing any further
moisture from entering into the region. High pressure is expected to
remain in place through at least mid week.

By Thursday, a strong surface low pressure system, associated with
the upper level closed low, will move across northern MN and toward
Lake Superior, dragging with it a cold front. This cold front will
extend from north to south across the entire conus, and is expected
to reach the Mississippi River Valley just after 12Z Thursday. Winds
ahead of this system will begin shifting to the SE and then
eventually to the S across our CWA during the day Thursday. This
will begin pulling moisture into the region which could result in
precip chances ahead of the approaching front. There is quite a bit
of disagreement among the GFS and ECMWF models however, as the GFS
keeps much drier air across the region during this time, preventing
any precip from reaching the CWA. Meanwhile the ECMWF shows more
moisture advection and a defined swath of precip through the Ohio
River Valley and points southward. Given the uncertainty and the
fact it is so late in the forecast period, stuck with only slight
chances of precip at this time, undercutting the model blend a bit.

Temperatures will start off near seasonable normals for Sunday and
Monday. However, airmass modification under mostly sunny skies will
help temperatures to increase a few degrees for Tuesday afternoon.
Then WAA will take hold for the remainder of the forecast period
ahead of the approaching system, with highs reaching the upper 70s
and low 80s. Overnight lows should remain in the low to mid 50s
generally throughout the period.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
ISSUED AT 750 AM EDT FRI SEP 30 2016

Fog and low stratus will continue to impact all TAF sites for the
next hour or two, with MVFR ceilings potentially hanging on until
late morning. VFR conditions should return by late morning/early
afternoon with light west winds. Will see a round of shower
activity move toward eastern Kentucky from the west this evening
into tonight, but too much uncertainty exists in timing/spatial
extent of this activity to warrant mention at this time. Cloud
cover will certainly be on the increase, but not sold on timing or
occurrence of sub-VFR ceilings. Fog will be a good bet in valleys,
but TAF sites look to have less of a chance with this dependent on
extent of any clearing or rainfall through this evening.

&&

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

$$

UPDATE...GREIF
SHORT TERM...GUSEMAN
LONG TERM...JMW
AVIATION...GUSEMAN



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