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Area Forecast Discussion (AFD)

Issued by Jackson, KY (JKL)

                            
000
FXUS63 KJKL 211137
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
737 AM EDT Wed Aug 21 2019

.UPDATE...
Issued at 737 AM EDT WED AUG 21 2019

There is some fog in spots so opted to add this for the morning.
The CAMs were off on the dawn convection, so opted to back off and 
go dry till around 18Z. The models continue to struggle with the 
potential for convection this afternoon, but will maintain slight 
to chance PoPs through the afternoon for now. Update was sent to
NDFD. 

&&

.SHORT TERM...(Today through Thursday)
Issued at 412 AM EDT WED AUG 21 2019

The morning surface analysis shows surface high remaining in 
control, with front well north from the Great Lakes to the Front 
Range. The upper level wave that helped slightly with convection 
yesterday is departing to the east. The CAMs were showing some 
convective development near dawn, but the HRRR has back off this 
idea. The only real trigger would be a very weak low level jet, 
but given the lack of forcing and instability only added a small 
area of slight chance of showers. There are a few more mid and 
high level clouds which should mitigate much in the way of fog 
production this morning. Even so, some areas may still have at 
least some ground fog as a result of the rain from yesterday.

Overall think the convection will be slow to start and will 
probably see more coverage later in the day. However, did limit 
this to slight and chance PoPs given the lack of better forcing. 
The MLCAPE could still climb into the 1500 to 2500 J/kg range this
afternoon depending on cloud cover, but the lack of shear will 
make this another pulse storm kind of day. This combined with 
DCAPE around 1000 J/kg would lead to mainly an isolated strong 
wind threat. This plays well with the SPC marginal risk that is 
placed across the area today. It should be another hot day in the 
upper 80s to lower 90s, but not as hot as yesterday given the 
cooler start and uncertainty on clouds.

Tonight more uncertainty arises in terms of convective coverage, 
as some of the guidance would suggest influence from upstream 
convection. Given this and guidance showing indication of height 
falls will keep chances of storms rolling through the night. The 
previously mentioned front will slide south into the Ohio Valley 
by Thursday and this will be a better focus for convection. The 
best chances during the day for storms will be in the Bluegrass. A
few strong storms can't be ruled out, as effective shear values 
climb into the 30 to 35 knot range. The question will be overnight
convection and cloud cover which could limit building 
instability. For now SPC keeps the Bluegrass in the marginal, 
which seems reasonable at this point given the uncertainties 
mentioned. 

.LONG TERM...(Thursday night through Tuesday)
Issued at 437 AM EDT WED AUG 21 2019

The models are in general agreement with an amplified long wave 
pattern to continue across the CONUS through the period. Details 
remain lower confidence by late this weekend and into early next 
week, with differing model solutions with regards to placement and
timing of the all important smaller scale features. Given this,
have stayed on the lower side of model guidance for the PoPs from
Sunday through Tuesday, allowing for more diurnal influence. 

Unsettled conditions will be on tap for eastern Kentucky Thursday
night through Friday night, as a cold front gradually advances
south across our area, with periods of likely PoPs. PWATs will be
in the 1.8 to 2.0 inch range at times, allowing for the potential
of locally heavy rainers; however, given the extended period of 
dry weather we have seen across the majority of the area leading 
up to this, any flooding threat would be more localized. 

This boundary will exit off into the Tennessee Valley this
weekend; however, general troughiness will linger either to our
east, or to our west, depending on which model you look at. As
such, have left in some diurnally influenced PoPs. By early next
week, a short wave trough will translate eastward across the Ohio
and Tennessee valleys, keeping the unsettled conditions going
across our area. Again, given the uncertainty with timing and
amplitude of these smaller scale features, have stayed a bit lower
than the blended guidance. Temperatures through the period will 
average near normal, with highs averaging in the low to mid 80s 
and lows in the 60s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
ISSUED AT 731 AM EDT WED AUG 21 2019

VFR remains the story for most sites with occasional fog creeping
into SME from nearby Lake Cumberland. VFR will remain the story
with a far amount of uncertainty on convective evolution through
the period. The models have been suggesting more isolated
convection this afternoon and perhaps more coverage late in the 
period. Given the uncertainty will only keep some VCTS late this 
afternoon. The winds will remain light for much of the period, but
winds of 5 to 8 knots out of the southwest are possible by this 
afternoon.

&&

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

$$

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