JKL issues Area Forecast Discussion (AFD) at Aug 4, 4:14 PM EDT381
FXUS63 KJKL 042014
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
414 PM EDT Sun Aug 4 2024
.KEY MESSAGES...
- Dense fog will once again impact some of the deeper valleys
overnight tonight.
- Hot temperatures and humidity will peak on Tuesday and Wednesday,
with afternoon heat indices near 100 degrees in some locations.
- Still quite a bit of uncertainty as to how Tropical Storm Debby
will impact eastern Kentucky late in the forecast period.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 411 PM EDT SUN AUG 4 2024
With high pressure the name of the game, it should continue to be a
somewhat uneventful short-term period. Meanwhile, TS Debbie will be
making landfall across NW Florida. Expect any impacts to remain well
to our south for the next couple of days, but that may change as we
head into the extended. With another day of sunshine and subsidence
on tap, expect a slight warm up again tomorrow, with highs in the
low 90s. Humidity will make it feel like the mid to upper 90s.
Perhaps the biggest concern during the short term will be the
continued fog development overnight. Temperatures will remain in the
mid and upper 60s both tonight and tomorrow night, with coolest
temperatures likely in the valleys. With light winds, high pressure,
and strong subsidence in place, this will combine with lingering
llvl moisture (i.e. from rains yesterday as well as from
river/streams in the deeper valleys) to create fog. Didn't change
forecast for tonight too much from what was already in there, with
the anticipation that some of the deeper valleys could see
widespread dense fog in places throughout much of the overnight.
This also matches up well with cross over temperatures, as deeper
valleys will likely drop into the low to mid 60s overnight, several
degrees below the daytime dew points. Did not include widespread
dense fog in for Monday night, however, given one more day of drying
and hopefully limiting the impacts. That being said, also not going
to rule it out, and will let the midnight shift re-evaluate as we
get closer in time based on the latest forecast of daytime dew
points and overnight temperatures.
.LONG TERM...(Tuesday through Sunday)
Issued at 412 PM EDT SUN AUG 4 2024
Confidence is high that the warming trend observed in the short term
forecast period will peak on Tuesday, as forecast guidance continues
to situate Eastern Kentucky on the eastern periphery of a
strengthening upper level ridge at this time. Under mostly sunny
skies, expect a strong diurnal temperature curve and localized
effects of terrain to drive the temperature forecast, with afternoon
highs in the low to mid 90s and overnight lows in the upper 60s. The
relative dryness of the continental airmass associated with the
aforementioned ridge will quell concerns of major heat-related
impacts, and the greatest chances for heat indices above 95 degrees
remain displaced to the west. However, urbanized and low-lying areas
may still experience apparent temperatures up to 100 degrees during
peak diurnal heating on Tuesday afternoon, and interests spending
extended periods of time outside on Tuesday should accordingly plan
to take breaks and stay hydrated.
On the other hand, confidence is still fairly low in the exact
evolution of Tropical Storm Debby as it interacts with a stalling
frontal boundary and associated troughing over the eastern
Appalachian Mountains for the rest of the long term forecast period.
On Wednesday, this frontal boundary is expected to traverse across
the forecast area, although it appears somewhat moisture-starved.
The greatest rain chances on Wednesday will be in the eastern half
of the forecast area during the afternoon hours (assisted by peak
diurnal heating). This boundary will linger over the Virginia border
in the following days, serving as a convergence point for moisture
streaming around the counter-clockwise circulation of Tropical Storm
Debby. Guidance has recently trended slower with Debby's inland
progression into the Carolinas, but models also continue to resolve
a westward or northwestward retrograding after landfall, which would
introduce related rain chances into our forecast area. However, the
spread in rainfall accumulation amounts remains quite drastic, with
the 25th percentile amount around a tenth of an inch and the 75th
around eight tenths through next weekend. Because the chances and
amounts of rain from this system will depend so much on its exact
track and how its winds/moisture transport orient against terrain,
no significant deviations from NBM PoPs were made at this time. The
greatest rain chances continue to populate on Friday afternoon, when
the eastern two-thirds of the forecast area will see slight to
chance PoPs (15-35). For the rest of the long term, PoPs generally
stay at or below 25% and peak in the far east. Regardless, the worst
hydrological impacts from this tropical complex should remain on the
eastern side of the Mountains.
Confidence is higher in the cloud coverage and temperature forecasts
for the days in the long terms. High cloud coverage should stream
off the Debby-stalled boundary complex and seep into SE portions of
the forecast area by Thursday afternoon and stick around until the
system ejects NE. Temps in these areas will be relegated to the mid
to low 80s, depending on terrain. Areas further west and north will
see less cloud coverage and thus higher temperatures, although the
passage of Wednesday's frontal boundary should keep high temps in
the mid to upper 80s and lows in the mid to upper 60s. These are
seasonably appropriate temperatures for early August.
&&
.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 202 PM EDT SUN AUG 4 2024
It took a bit longer than expected, but low stratus and fog did
eventually dissipate late this morning, leaving developing fair
weather CU in it's place. This CU has quickly spread across much
of the region, with up to 50% coverage of the sky. This has lead
to some SCT to BKN decks of MVFR conditions, which will likely
continue through much of the afternoon, then quickly dissipate in
the evening. Given the ongoing humidity and continued llvl
moisture, in addition to strong subsidence and light winds
overnight, expecting another night of dense valley fog and
potential for areas of fog elsewhere. Tried to match the VIS
accordingly, as well as including a low cloud deck. Since all the
TAF sites were affected by fog in the last 24 hours, went ahead
and made sure they were all included in the fog impact for tonight
as well. This may result in some airport closures after midnight
through early morning, before the fog begins to lift at daybreak
and eventually dissipates during the late morning again. Guidance
only suggested high clouds tomorrow, but woudn't be surprised with
more fair weather CU developing during the afternoon in addition.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...JMW
LONG TERM...MARCUS
AVIATION...JMW
Source:
JKL issues Area Forecast Discussion (AFD) at Aug 4, 4:14 PM EDT---------------
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