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Area Forecast Discussion (AFD)

Issued by Jackson, KY (JKL)

                            
000
FXUS63 KJKL 190303 AAB
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1103 PM EDT Sun Aug 18 2019

.UPDATE...
Issued at 1055 PM EDT SUN AUG 18 2019

Some minor adjustments have been made to hourly temperatures,
mainly for some southeastern valley locations that had fallen a
degree or two below the previous forecast. Overnight lows still
look on target with mid 60s for valleys and near 70 on coalfield
ridges. Since crossover temperatures were generally in the low to
mid 60s with even some upper 50s, fog should just be confined to
the river valleys and less extensive than some of the earlier LAMP
and Consshort guidance. In fact, the LAMP guidance has trended
toward less reductions in vis in fog for a few stations such as
JKL as well.

UPDATE Issued at 825 PM EDT SUN AUG 18 2019

Hourly grids were updated to account for recent satellite, radar,
and observation trends. Isolated convection that had developed 
late in the afternoon and early evening in the counties near the
TN and VA borders has dissipated as sunset approached. Overall, 
no substantial changes were made at this time. 

&&

.SHORT TERM...(This evening through Monday night)
Issued at 430 PM EDT SUN AUG 18 2019

19z sfc analysis shows high pressure over eastern Kentucky and
its subsidence has helped to keep the clouds to a minimum 
supporting a hot afternoon as readings made it into the 90 to 95 
degree range for many places. Dewpoints have actually come down 
during the afternoon due to a mix down of somewhat drier air and 
are now in the low to mid 60s, in general. This has yielded heat 
indices mainly in the 95 to 100 degree range - despite the higher
temperatures - below the stifling heat of a few weeks back. Winds 
have been mainly light from the southwest this afternoon with a 
few gusts to 10 kts. Some pinprick thunderstorms have also popped
up in the far south and these could spawn a few additional ones 
into the early evening hours. For this reason have included a pre-
first period in the zones to cover them for the next several 
hours.

The models are in pretty good agreement aloft through the short 
term portion of the forecast period. They all depict one last 
shortwave to brush by to the north of Kentucky tonight. This wave
passes before higher heights come north as the southern ridge 
builds further into the start of the new work week. The mid level 
flow slows during this time, as well, though it does set up a 
divergent pattern that will need to be contended with on Tuesday 
when the next shortwave moves through the Ohio Valley. Given the 
general model agreement aloft will again favor the NBM and its 
blended solution with some consideration of the CAMs in the near 
term. 

Sensible weather will feature a warm evening with dying isolated 
convection and clearing cu toward sunset. This will set up a mild 
night again beneath some high clouds from storms to the northwest
- likely limiting the fog formation to the river valleys. In 
addition, the high clouds will have a moderating effect on our 
ridge to valley temp differences through the night. Look for 
another hot day on Monday, but the dewpoints should be a tad more 
moist and more clouds keeping readings a tad lower. Again some 
higher terrain storms will be possible in the southeast in the 
afternoon but kept PoPs just below 15% there. Late in the day some
storms from the northwest could make it into the area before also
dying off - for this have allowed slight chance PoPs but also 
kept them into the night northwest as boundaries stick around. 
Again a smaller ridge to valley difference can be expected Monday 
night with more clouds and higher dewpoints in place. More clouds 
should also help keep fog to a minimum - again limited to the 
river valleys. 

The NBM was used as the starting point for all the grids with only
minor adjustments to temperatures at some points along with minor
ridge and valley differences added tonight and Monday night. For 
PoPs, again focused on the higher southeast terrain at peak 
heating into the evening - above NBM - and also the northern 
activity Monday afternoon also exceeding the model's numbers. 

.LONG TERM...(Tuesday through Sunday)
Issued at 300 PM EDT SUN AUG 18 2019

The weather pattern in the extended will feature a large ridge of 
high pressure situated over the southeast CONUS, mid atlantic region 
and the Tennessee valley to start things off. We will also see a 
large trough of low pressure aloft moving across the Great Lakes and 
Ohio Valley regions from mid week onward. This trough will 
eventually make its way into New England by next weekend. The trough 
should be strong enough to break down the surface ridge, thereby 
pushing it off to our east as the week wears on. This low pressure 
system, and its attendant slow moving frontal boundary, will bring 
rain chances to eastern Kentucky each day in the extended. The best 
chances for rain should be from Wednesday through late Thursday 
evening, as the front gets temporarily hung up over the area. We 
should see showers and storms tapering off steadily late Thursday 
night and Friday, as the front finally drifts off to our south and 
southeast. The front should remain close enough to the area to keep 
rain chances in the picture going into next weekend as well.

High temperatures will likely start off well above normal to begin 
the period, with highs in the upper 80s and lower 90s expected for 
Tuesday and Wednesday. After that, we should see a return to normal 
or maybe even slightly below normal highs to end the week and going 
into the weekend. Highs on those days are forecast to reach into the 
low to mid 80s for most locations. Nightly lows will start off only 
falling into the upper 60s to lower 70s, with low to mid 60s min 
readings expected from Wednesday night into the weekend. 

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 825 PM EDT SUN AUG 18 2019

VFR conditions will prevail into Monday, aside from some MVFR or 
worse fog seen in the deeper river valleys between 06 and 13z. 
Some diurnally driven cumulus at 4-6k feet agl are anticipated
from around 16Z on. South to southwest surface winds of less than
10kt are expected.

&&

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

$$

UPDATE...JP
SHORT TERM...GREIF
LONG TERM...AR
AVIATION...GREIF/JP