Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 201400
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1000 AM EDT Sat May 20 2017

.UPDATE...
Issued at 1000 AM EDT SAT MAY 20 2017

Forecast seems to be on a pretty good track this morning. Made
some minor adjustments to the sky cover based on latest trends,
and also freshened up the near term grids with the latest
observations. All changes have been published and sent to
NDFD/web. A new forecast package was also sent out to remove any
morning fog wording.

UPDATE Issued at 748 AM EDT SAT MAY 20 2017

Freshened up the POPs through early this afternoon, based on some
of the higher resolution model guidance. The weather should
remain fairly quiet until closer to 18z, when isolated to
scattered convection is expected to begin across portions of the
area.

&&

.SHORT TERM...(Today through Sunday)
Issued at 342 AM EDT SAT MAY 20 2017

The latest surface map features a quasi-stationary front aligned
from central Missouri to near or just north of the Ohio River.
This stems from low pressure centered in eastern Kansas. Aloft, an
upper level low is shifting from the front range of the Rockies to
the high Plains, with ridging sharping up from the Great Lakes
down to the southeastern CONUS.

This upper level low will gradually spiral northeast through the
Plains and eventually to the south central Canadian border by
late Sunday. Surface low pressure will follow suit, tracking just
a bit off to the east and southeast, reaching the northern Great
Lakes by the end of the period and dragging a cold front across
the Commonwealth.

Eastern Kentucky should see less convective coverage today, as
heights recover aloft, and slightly drier air works in at the low
levels. Expect the better coverage to be towards the north this
afternoon, where the surface boundary will be easing north as a
warm front. Highs today will rebound into the mid and upper 80s.
As we head into tonight, there likely be ongoing storms off
threatening to our west, but the latest CAMs suggest diminishment
as they attempt to make into our area after sundown. Any
convection that remains organized could potentially be on the
stronger-side. During the overnight, a low level jet will bring an
increase in convective coverage from the southwest after midnight,
with less chances in the east. Lows will be in the low to mid
60s.

A surface cold front will move through eastern Kentucky late
Sunday. Forcing is not overwhelming, but there will be plenty of
moisture, so some locally heavy rain/flooding will be a concern,
especially across locations that have already seen heavy rainfall
in the past 24 hours. Will play this up in the HWO. Plenty of
clouds and precipitation will keep the highs suppressed, generally
in the 75 to 80 degree range.

.LONG TERM...(Sunday night through Friday)
Issued at 344 AM EDT SAT MAY 20 2017

The period will be met with the cold front pushing east across the
region and POPs slowly reducing from west to east through the
night. While some lingering showers will reside in the far east
early Monday, most will see clearing through by the afternoon.
This as a surface high pressure builds east in the wake of the
cold front. This will lead to some slight temperature splits for
Monday night into Tuesday morning. After this this the models
diverge on solutions, as they struggle with phasing by mid week.
The issue is the divergence in the upper level evolution will have
substantial implications on the surface features and sensible
weather. This leads to very differing timing on cyclogenesis and
overall evolution of surface boundaries and potential surface
lows. Therefore, will keep several rounds of chance POPs that the
blend has to offer until better model agreement can be seen.

This upcoming pattern will be fairly anomalous with NAEFS
Standardized anomaly tables showing 500mb heights getting close to
3 deviations below normal. Therefore, despite the differences
described above the lowering heights from the amplified pattern
and several rounds of precip/clouds will lead to near to below
normal temperatures through the period. Matter of fact the
potential exists for below normal temperatures at times over the
next 6 to 10 days based on the forecast from the CPC and based on
the GEFS 6-8 day CIPs analog. Now the coolest day in terms of
afternoon highs will be Thursday when temperatures will top out in
the mid to upper 60s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
ISSUED AT 748 AM EDT SAT MAY 20 2017

IFR or worse fog will lift and dissipate across the deeper river
valleys by 13z. Will hold onto mainly VFR conditions through the
rest of the period. Isolated to scattered showers and
thunderstorms will likely develop across portions of eastern
Kentucky after 17z. Have introduced a VCTS at all sites. The best
precipitation chances will move in from southwest to northeast
across the area between 09 and 12z Sunday, as a cold front draws
closer from the west. Winds will remain at around 5 kts or less
through the period.

&&

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

$$

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



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