JKL issues Area Forecast Discussion (AFD) at Jul 4, 10:15 PM EDT945
FXUS63 KJKL 050215
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1015 PM EDT Thu Jul 4 2024
.KEY MESSAGES...
- Though an isolated thunderstorm cannot be ruled out through
tonight, better chances for thunderstorms will return Friday,
mainly during the daylight hours.
- A few thunderstorms Friday afternoon to early evening could
produce locally heavy rainfall and strong to damaging wind
gusts.
- Somewhat cooler and less humid weather arrives behind a cold
front over the weekend.
- Warmer and more humid conditions will make a noticeable comeback
on Monday and continue into next week, along with a potential
for more thunderstorms.
&&
.UPDATE...
Issued at 1015 PM EDT THU JUL 4 2024
SPC Mesoanalysis depicts elevated instability, but also plentiful
convective inhibition across the forecast area. Given model
trends, have lowered PoPs to primarily low-end slight chance PoPs
for the overnight. There were no other significant changes
otherwise.
UPDATE Issued at 610 PM EDT THU JUL 4 2024
Thunderstorms in eastern KY have diminished in both coverage and
intensity over the past hour and Severe Thunderstorm Watch 505 has
been allowed to expire early. Minor adjustments were made to the
forecast based on recent radar and satellite trends.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 549 PM EDT THU JUL 4 2024
Convection that had worked across northern sections of the area,
has weakened after producing some locally heavy rain and a couple
instances of wind damage as well. Current trends suggest
convection in the north and southeast should work east toward VA
and WV and diminish over the next couple of hours while
convection in south central KY works toward the Lake Cumberland
area. With a warm and moist airmass in place, an isolated shower
or storm could develop outside of these areas, but with meager mid
level lapse rates and weak shortwave to shift east over the next
couple of hours coverage of all convection should generally wane
toward sunset. With convection in the severe thunderstorm watch
having dwindled some cancellations will be upcoming.
An upstream cold front will approach the lower OH Valley tonight
and work across the OH Valley region including the Commonwealth on
from Friday into Friday night ahead of a more robust shortwave
trough. Some showers or storms will remain possible in the warm
sector tonight, though coverage should peak again on Friday
afternoon to early evening ahead of the cold front and associated
mid level wave. Pre convective MLCAPE may be as high as 2000 to
2500 J/kg with bulk shear during the afternoon on the order of 25
to 35KT. Mid level lapse rates should be 6C/km or less, but low
level lapse rates could be in the 7C to 8C/km range given
sufficient heating into the 80s to perhaps near 90. Some CAMS
such as the 18Z HRRR suggest the potential for some potentially
robust activity from midday into the afternoon or a bit later than
earlier runs and wind gusts should be the primary threat and
locally heavy rain also possible with PW in the 2 to 2.25 inch
range. SPC has a marginal risk for severe thunderstorms on Friday
and this will continue to be highlighted in the HWO.
As the front shifts east on Friday night along with the associated
shortwave trough, chances for convection will diminish from west
to east as the night progresses.
.LONG TERM...(Saturday through Thursday)
Issued at 530 PM EDT THU JUL 4 2024
The period is expected to begin with broad upper level troughing
from Canada south into the Central Conus/MS Valley with a narrow
axis of ridging from the Gulf of Mexico to just east of the
eastern seaboard while another stronger ridge is expected to be
anchored along the west Coast of the Conus. At the surface, behind
a cold front that will have shifted to the southeast, a ridge of
high pressure extending across portions of the Central Conus is
expected to be nosing into the OH Valley region and ushering in a
somewhat cooler and drier airmass.
Saturday through Sunday night, an upper level low and associated
shortwave trough should lift east/shear on out to the east and
northeast on Saturday. A gradual trend of height rises into the
OH Valley, Appalachians, and OH Valley by Saturday night and
Sunday is forecast with the trough over the Central Conus
sharpening up a bit in between ridging centered over the eastern
Gulf of Mexico into the southwest and ridging over the western
Conus. At the same time, Beryl should be working across portions
of the Bay of Campeche into the Gulf of Mexico. Sfc high pressure
ridging sliding across the OH valley and then toward the eastern
seaboard combined with a general trend toward 500 mb height rises
and a drier airmass will lead to a period of drier weather and
also somewhat cooler and less humid conditions for eastern KY.
From Monday to midweek, however, return flow of more warm and
humid air should return between high pressure near the eastern
seaboard and the next cold front and mid level trough and
preceding shortwaves that generally pass to the north and
northeast. A trough at 500 mb will linger to the southwest into
the Southern Plains area. Convection may occur as early as Monday
afternoon, especially in the more southern locations, but a peak
is anticipated on Tuesday to Tuesday night ahead of the next
shortwave that moves east of the MS River and across the Great
Lakes, parts of the OH Valley, the Northeast, and mid Atlantic.
How much moisture from the remnants of Beryl is drawn northeast
from the Southern Plains is uncertain, but regardless, sufficient
return moisture should reach eastern KY for possible multiple
rounds of convection from Monday evening into Wednesday and the
cold front itself may tend to become more diffuse as it reaches
eastern KY on Wednesday. Guidance suggests Monday will the
warmest of the Monday to Wednesday timeframe with highs near the
90 degree mark for many areas, before convection and clouds should
keep highs in the 80s on Tuesday and Wednesday.
Wednesday night to Thursday, the axis of troughing at 500 mb may
remain west of the OH Valley as the cold front becomes diffuse
by this timeframe. Another cold front could approach the OH
Valley at that point and some disturbances may cross the area as
well. Chances for any convection should peak on Thursday
afternoon, although some ECMWF guidance for instance suggests it
could be dry on that day.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 705 PM EDT THU JUL 4 2024
Showers and thunderstorms may impact areas on the outer edge of
the forecast area, mainly toward KSME and possibly KLOZ, this
evening, though this is very low confidence. Much greater coverage
of showers and storms is expected during the daylight hours
Friday, especially after 15z and lasting through much of the rest
of the TAF period. Expect sub-VFR conditions in these showers and
thunderstorms along with occasionally gusty and erratic winds,
but confidence in timing in placement and severity of conditions
is too high uncertainty to include in the TAFs at this time.
Otherwise, valley fog is a possibility tonight as well following
rain that has fallen today. The extent of cloud cover overnight
could be a limiting factor, but reductions to MVFR or IFR are
possible and if clouds are few LIFR or below airport mins cannot
be ruled out. At this point this should have little impact on the
TAF sites. Winds will average 10KT or lest outside of convection,
from southwest to west to begin the period, before trending to
southwest to south around or after 00Z.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...CMC
SHORT TERM...JP
LONG TERM...JP
AVIATION...CMC
Source:
JKL issues Area Forecast Discussion (AFD) at Jul 4, 10:15 PM EDT---------------
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