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Area Forecast Discussion (AFD)

Issued by Jackson, KY (JKL)

FXUS63 KJKL 171410 AAA

National Weather Service Jackson KY
1010 AM EDT Sat Aug 17 2019

Issued at 1010 AM EDT SAT AUG 17 2019

13z sfc analysis shows high pressure in place through eastern 
Kentucky. This should keep the weather quiet today and convective
clouds to a minimum. However, some high clouds will periodically
drift through the area from storms to the west through the day. 
Still cannot rule out a shower or storm surviving long enough to 
sneak into our area - later in the day - mainly in the northwest 
but not out of the question elsewhere. For now will stick with the
limited PoPs in the northwest parts as outlined in the HWO. The 
rest of the forecast is on track, as well, now that the fog has 
dissipated and temperatures have bounced off the lows rebounding 
into the low and mid 70s most places. Dewpoints, meanwhile are 
generally in the mid 60s while winds are light and variable. Have 
updated the T and Td grids with the latest obs and trends. These 
updates have been sent to the NDFD and web servers along with a 
fresh set of zones nixing the fog. 

UPDATE Issued at 812 AM EDT SAT AUG 17 2019

Overall, the forecast remains on track. Fog will be burning off in
the next hour or so. Mainly just freshened up the hourly
temperatures as well as sky cover to account for the latest trends
in observations and satellite imagery. The latest HRRR model runs
are showing less of a chance of storms later this afternoon
across our area, as most of the convection upstream stays on more
of an east northeast course across the Ohio Valley. Will maintain
the slight chance PoPs for now, and await further model guidance
before lowering.


.SHORT TERM...(Today through Sunday)
Issued at 413 AM EDT SAT AUG 17 2019

Surface high pressure is currently sprawled across the eastern
Ohio Valley down across the Tennessee Valley. A quasi-stationary
boundary is aligned from the Plains eastward into the Midwest/Ohio
Valley region. Aloft, mainly zonal flow is found across the 
Plains and into most of the Mississippi Valley, with embedded 
short wave energy noted within the flow. Better ridging is found 
across the U.S./Mexico border, with a deeper short wave trough 
moving in across the Pacific Northwest/northern Rockies. In 
eastern Kentucky, mostly clear skies reign besides some passing 
higher level clouds. River valley fog is also less extensive 
compared to last night at this time. Temperatures currently range 
from the low to mid 60s in the valleys, to the upper 60s on the 

Today will feature a mostly sunny start across the area, with
patchy valley fog burning off by around 9 am. As we head into the
afternoon, most of the higher resolution model guidance shows the
potential for some convection trying to move in from our 
northwest. This activity will likely weaken as it approaches; 
however, some residual outflow may be enough to initiate at least 
isolated convection. As such, will include some slight chance 
PoPs for the northwestern portion of our area. Highs today will
be in the upper 80s to around 90 degrees.

Any isolated convection will die out by dusk, with clearing skies
and patchy valley fog occurring once again. Lows will be a bit 
milder compared to previous nights, generally in the mid to upper
60s. Heights will build in better across our area on Sunday, 
keeping a lid on most convection. Temperatures will be a bit
warmer, with most locations peaking at around 90 degrees. 

.LONG TERM...(Sunday night through Friday)
Issued at 413 AM EDT SAT AUG 17 2019

We will be under relatively zonal flow with a hint of ridging
moving in from the Southern Plains to start the new work week. The
models have been quite aggressive with afternoon high temperatures
given the relatively lower end upper level ridge forecast. We have
seen 2 90 degree days here at JKL this summer and those came as a
result of a stronger upper level ridge right over top of Kentucky.
The CIPs analog guidance also backs this up showing lower end
chances of seeing greater than 90 degrees across eastern Kentucky.
The other fly in the ointment will be the potential for afternoon
showers and storms and resulting cloud cover which would cut into
the maximum afternoon highs both days. Given this did opt to
undercut the National Blend of Models (NBM) Monday and Tuesday in
particular, with possibly too much of this blended toward the very
aggressive RAW ECMWF. That said, the RAW numbers from the ECMWF
are not supported by the ECMWF MOS GUIDE and the higher MOS GUIDE
ensemble is lower than the regular operational RAW numbers.

By mid to late week the models suggest a cold front will drop
south and bring better chances of storms to the area by Wednesday.
Given the better agreement among the guidance opted to keep the
lower end likely PoPs presented by the NBM. This front will usher
in a cooler airmass, with afternoon highs coming in closer to
normal for JKL/LOZ for this time of year. The real question is how
far south does the front push and is it enough to keep the area
completely dry by the end of the week. Based on the latest
guidance this may be true under northerly flow and strong surface
high moving across the Ohio Valley. However, did keep some lower
end PoPs near the TN/VA border given the uncertainty this far out.
Either way the Bluegrass and possibly farther south stand to see a
nice end to the week, with afternoon dewpoints dropping into the
upper 50s to lower 60s.


.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)

VFR conditions will prevail through the majority of the period.
The only exception will be some MVFR or worse fog seen in the
deeper river valleys. This will burn off by 13z, and will likely
re-develop after 06z tonight. In general, this fog should steer 
clear of the TAF sites. Once the fog burns off this morning, some
diurnally driven cumulus ranging from 4-6k feet agl will be seen.
Winds will average less than 5 kts through the period.