Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 210603 AAD

National Weather Service Jackson KY
203 AM EDT Wed Jun 21 2017

Issued at 155 AM EDT WED JUN 21 2017

Thicker cirrus is streaming from West Tn east northeast to the
KY/V border region into the Central Appalachians. A surface ridge
of high pressure remains in control across the Appalachians with
the region in a seasonably moist airmass between weak cold front
or outflow boundary north of the Ohio River and nearly stationary
boundary from east TX east northeast to the Delmarva which is the
leading edge of the much deeper tropical moisture to the south.
This moisture is being transported into the Gulf states around
Tropical Storm Cindy.

Sky cover has been increased a bit across the south to account for
the greater abundance of cirrus initially although guidance
suggests that this should decrease toward dawn. Additional debris
mid level clouds could cross the OH River and move into the
northern part of the area as well. Temperatures in some valley
locations were not dropping as quickly as the inherited forecast
and have been increased a couple of degrees for the next few
hours. However, min T in these valley areas was only raised a
degree or two as a thinning in clouds is expected prior to dawn
more to the upper 50s versus some mid 50s. Overall, this update
led to no substantial changes.

UPDATE Issued at 1047 PM EDT TUE JUN 20 2017

WSR-88D still picking up on a few isolated rain showers and/or
sprinkles. These will remain light and most spots will remain dry
tonight. Updated to allow a bit more time on the sprinkles and
also updated clouds with latest obs and satellite trends. Also,
the clouds are playing a role in keeping temperatures a bit warmer
than the current temperature curve. Therefore, adjusted the curve
some to better match trends.

UPDATE Issued at 857 PM EDT TUE JUN 20 2017

Despite surface high pressure, a 500MB wave and 300mb divergence
is just enough to POP off a rain shower or sprinkle this evening
based on WSR-88D radar this hour. The HRRR seems to be handling
this fairly well and will somewhat lean toward it with edits. For
now will update to add in sprinkles at most for a couple of hour.
These will be showers will be light and are expected to dissipate
over the next couple of hours.

UPDATE Issued at 625 PM EDT TUE JUN 20 2017

Surface high pressure continues to build into the region and
matter of fact the highest pressure reading nearby is at CSV in
the TN Valley region. Overall this and mixing will lead to a drier
night and based on crossover temps not as much fog. However, while
the CU will dissipate and we will be left with mostly high clouds
streaming in from the SW. No major changes needed for this update
but did load in the latest obs and trends.


.SHORT TERM...(This evening through Wednesday night)
Issued at 359 PM EDT TUE JUN 20 2017

The latest surface map features broad high pressure across the
mid-Mississippi Valley, with Tropical Storm Cindy located across
the central Gulf of Mexico. Aloft, a strong ridge remains poised
across the Desert Southwest, with troughing in the northeastern
quadrant of the CONUS. Eastern Kentucky has been enjoying dry
weather, with temperatures in the low to mid 80s and dew points
down as low as the lower 50s in places at times.

Dry weather will continue through the rest of the short term, as
high pressure remains nosed in from the east southeast through the
column. Tonight will feature a mostly clear night, with lows
ranging from the mid 50s in some of the cooler valleys, and lower
60s on the ridges. Wednesday will feature a warmer day, with highs
in the mid 80s, and dew points also a bit higher.

The moisture will make a bigger increase through Wednesday night,
as thicker high clouds stream in from the approach of Cindy. Lows
will be in the mid to upper 60s.

.LONG TERM...(Thursday through Tuesday)
Issued at 359 PM EDT TUE JUN 20 2017

The extended portion of the forecast begins on Thursday with the
upper level pattern favoring a more northern track with the jet
leaving the central and southern CONUS under weak flow to begin the
extended. Focus of the extended will be on the approach of the
remnants of or rather a still organized Tropical Depression
possible moving into Kentucky. Models have wavered a bit on the
track and QPF amounts but overall have kept a consistent time period
of rainfall. As the surface tropical low track north and northeast
around the mid level ridge parked over the southeastern CONUS it
will track east into KY and the TN Valley. At this point the system
interacts with a cold front dropping from the western Great Lakes
southeast into the Ohio Valley. Models have indicated, though
slightly inconsistent on the placement of the heaviest band of
precip, that this interaction with the front and the deep rich
tropical moisture will produce the heaviest rainfall during the Sat
00Z to 12Z period. Model soundings during this time indicate a 2
inch plus PWAT over eastern Kentucky. However, the inconsistency of
models and the lessened QPF of WPC 12Z solution has made the case to
reduce QPF a bit so added a 50% blend to the super blend from the
WPC run. Thus have gotten a more reasonable QPF amount and in
agreement with the neighboring offices. So will continue to mention
the heavy rainfall threat in the HWO for Friday through Saturday
night with the best chance being Friday night into Saturday.

By Sunday, expect a brief period of dry weather before the next
disturbance tracks east across the mid MS Valley into eastern
Kentucky by Sunday afternoon. The front will hang up along the
middle Appalachians keeping the chance of precip lasting from Sunday
afternoon into Monday afternoon. Confidence at this point is not
very high given the uncertainty of the track of the remnants of
Tropical system Cindy. Thus pop chances will be slight for Sunday
night through Monday night.


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

Surface high pressure centered to the east and southeast will
keep VFR in place through the period. We will remain VFR for the
period as surface high pressure remains in control. Any valley fog
should not affect the TAF sites as Tuesday afternoon crossover
temps are not likely to be met. Some generally high thin cu is
possible on Wed afternoon and will re evaluate this potential for
12Z issuance, but kept TAFs simple VFR one line for now. Winds
will remain light at 10KT or less through the period.




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