JKL issues Area Forecast Discussion (AFD) at Jul 25, 8:10 PM EDT201
FXUS63 KJKL 260010 AAA
AFDJKL
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
810 PM EDT Thu Jul 25 2024
.KEY MESSAGES...
- There is an increasing threat for excessive rainfall from
multiple rounds of showers and thunderstorms Sunday through
Tuesday, which may lead to the potential for flooding concerns.
- High temperatures will average near normal (mid 80s) through the
middle of next week.
&&
.UPDATE...
Issued at 745 PM EDT THU JUL 25 2024
23Z sfc analysis shows a weak frontal boundary through eastern
Kentucky and this is supporting a few lingering, and slow moving,
pockets of convection. Otherwise, under partly cloudy skies,
temperatures are running in the upper 70s to lower 80s. Meanwhile,
amid light and variable winds, dewpoints continue to be elevated
in the low to mid 70s south of the boundary but in the low to mid
60s north - over the bluegrass region. Have updated the forecast
mainly to add in the latest radar imagery and CAMs details through
the night. Did also include the current obs and trends for the
T/Td/Sky grids. These minor adjustments have been sent to the NDFD
and web servers along with a freshening of the zones and SAFs.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 350 PM EDT THU JUL 25 2024
Cold front moving south across the Ohio River corridor will slowly
approach the Tennessee border by late tonight or early Friday
morning. Isolated to widely scattered convection will move southeast
along and ahead of the front this afternoon. As the front continues
to track south, showers and thunderstorms will increase in coverage;
however, the best chances (50-60%) for storms continues to exist
along the eastern high terrain. The lowest chances (20-30%) are in
the Bluegrass Counties. As have mentioned in previous discussions,
widespread severe weather isn't expected today as large scale
forcing is lacking; nonetheless, can't rule out a storm getting a
little frisky and putting down some stronger winds. PWs have lowered
from previous forecasts and max out in the 1.5" to 1.6" range, which
lowers the excessive rainfall risk a bit. However, areas that see
repeated rounds of shower/storm activity could still see localized
hydro issues. The front will gradually exit the area late tonight
but clouds will linger through much if not all of the overnight.
This could limit the amount of fog development and keep surface
temperatures relatively warmer. However, with moisture from rainfall
being present, fog will more than likely develop.
The front stalls across the far southern part of the CWA, very close
to the TN border, for Friday. With greater confidence in the front
stalling more south of previous forecasts, precipitation chances
were confined to areas south of the KY-80/Hal Rogers Parkway, with
the best chances for showers and thunderstorms right along and
south of the TN border. Despite most areas trending drier, high
PWs approaching 1.75" will continue to exist along the immediate
TN border; therefore, can't completely discount localized
flooding due to multiple rounds of rain.
Friday night will bring another chance of valley fog but cooler
temperatures are expected as post-frontal CAA will bring
temperatures in the low to mid-60s. High pressure begins to nudge
in from the north and will bring a quiet end to an active forecast
period.
Overall, the forecast period will be highlighted with periods of
showers and thunderstorms today, becoming increasingly confined to
the far southern parts of the forecast area Friday, with a drying
trend for the remainder of the forecast area through Friday night.
Temperatures will be mostly seasonal with temperatures in the mid
to upper 80s and lows in the low to mid 60s, though a few upper
50s are possible in the coolest locations Saturday morning.
.LONG TERM...(Saturday through Thursday)
Issued at 442 PM EDT THU JUL 25 2024
The 25/12z model suite 500H analysis beginning Saturday morning
shows upper level ridging over the Eastern Gulf of Mexico building
northward across the Commonwealth and merging with an ~591 dam high
passing through the Great Lakes. A trough/weak upper low is found
over northeast Texas and eastern Oklahoma. Further upstream, a
prominent trough axis is moving inland from the West Coast. At
the surface, a weak frontal boundary extends form the North Carolina/
Virginia border to over southcentral Kentucky and then arcs north
and west into the Upper Midwest. To the north and east of the
boundary, departing high pressure is centered over the Mid-
Atlantic states.
That surface high will shift east and largely dissipate on Sunday
as the ridging aloft is squashed in the face of the weak upper
low shifting northeastward and merging with the advancing West
Coast trough while another upper low develops off the Mid-
Atlantic coast and lifts toward Southern New England. Initially,
PWATs north of the frontal boundary will be quite dry on Saturday
morning ~ 0.75 to 1.00 north of the Cumberland Basin; and,
further south in the vicinity of Lake Cumberland, they are still
favored to only be around 1.25 inches or less. However, as that
ridging departs and dissipates, the frontal boundary will likewise
cave to strengthening, moisture-laden southwesterly flow ahead of
the upstream troughing. Ensemble means favor PWATs soaring to
between 1.8 to 1.9 inches (or over the 90th percentile relative to
climatology) by Monday afternoon though multiple deterministic
members suggest PWATs rising to 2.0-2.2 inches. Meanwhile, lifting
processes will be enhanced by a favorably positioned upper level
jet over southern portions of the forecast area by Sunday
afternoon and across all of eastern Kentucky on Monday. Modeled
kinematic and thermodynamic profiles favor sluggish cell motions
and possible convective backbuilding. This along with efficient
deep warm layer rain processes spells a threat for torrential
downpours which could be more persistent than what our area has
experienced recently. In fact,this setup could pose the most
substantial flash flood threat that we have seen in at least
several months, especially for those locations that have seen
their soils moistened by the repeated rounds of rainfall during
the last couple of weeks. WPC has hoisted a Slight Risk for
excessive rainfall across southern portions of the forecast area
on Sunday and all of southeast Kentucky on Monday. The risk for
heavy rainfall will likely continue until Tuesday night or
Wednesday when the upper level trough axis shifts east of our
area, though an associated cold front will probably linger
somewhere over the Ohio Valley thereafter.
At this point, it is impossible to pinpoint where the heaviest
rains will fall early next week given the mesoscale and orographic
features that could come into play. It is also important to keep
in mind that there is still plenty of time for the overall pattern
to evolve differently and keep the heavier rainfall out of our
area. However, those with interests in flood-prone areas,
especially near smaller creeks and streams, are encouraged to
monitor the forecast for early next week.
As for sensible weather, look for just a stray chance (10 to 20%)
for a shower or thunderstorms over far southern Kentucky on
Saturday afternoon. Most place should see dry conditions and
mostly to partly sunny skies. Much higher rain chances (50 to 70%)
return from the southwest on Sunday/Sunday Night as deep moisture
surges back across eastern Kentucky. From Sunday afternoon
onward, the greatest convective coverage is expected during the
afternoon and evening coincident with diurnal heating and
destabilization, though there will also be the threat for
convection at night too when disturbances pass. Temperature-wise,
look for highs in the mid 80s to around 90 on Saturday.
Thereafter, look for highs to range mostly in the mid 80s through
Wednesday while lows bottom out in the mid 60s to around 70 for
most places. With the return of drier air, expect highs to return
back to the upper 80s to near 90 by next Thursday, though there is
still a chance (30 to 40%) for shower and storms.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 810 PM EDT THU JUL 25 2024
Terminals are all at VFR conditions early this evening. A cold
front is slowly moving south across the area triggering isolated
to widely scattered showers and a couple of thunderstorms, any of
which could briefly reduce conditions to MVFR or lower. However,
will keep VFR conditions in the prevailing forecast through the
evening and into the overnight. Fog will develop tonight behind
the cold front, but confidence is low as to how widespread and
severe the fog will be outside of the valleys. Did allow for a
tempo to low clouds and MVFR fog at KSJS late tonight through
dawn. With the exception of gusty and erratic storm outflows,
light and variable winds (generally from a northerly direction)
are expected to prevail through the forecast period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GREIF
SHORT TERM...CMC
LONG TERM...GEERTSON
AVIATION...CMC/GREIF
Source:
JKL issues Area Forecast Discussion (AFD) at Jul 25, 8:10 PM EDT---------------
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