JKL issues Area Forecast Discussion (AFD) at Jul 15, 11:06 AM EDT023
FXUS63 KJKL 151506
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1106 AM EDT Mon Jul 15 2024
.KEY MESSAGES...
- Hot and humid weather will bring heat indices ranging from the
upper 90s to the lower 100s to many locations today and
Tuesday.
- The next significant chance of rain area wide arrives
Wednesday.
&&
.UPDATE...
Issued at 1106 AM EDT MON JUL 15 2024
Only minor tweaks made to the grids in this late morning update.
Touched up the warming curve for this afternoon after loading in
the latest surface obs. Also, removed mention of fog in morning
text and radio products. Grids have been saved and sent.
UPDATE Issued at 655 AM EDT MON JUL 15 2024
Satellite shows increased cloud cover across much of the forecast
area south of Interstate 64, so increased Sky grids to account for
this. Also increased and expanded PoPs slightly for this afternoon
especially. Other changes were minimal, with the latest hourly
observations used as initialization for the forecast grids.
&&
.SHORT TERM...(Today through Tuesday)
Issued at 448 AM EDT MON JUL 15 2024
Eastern Kentucky continues to reside along the northwestern edge of
upper-level ridging and surface high pressure over the Southeast US
and adjacent western Atlantic Ocean. Meanwhile, a broad upper level
trough over central North America gradually sharpens and digs
southeast toward the Midwest through midweek, with warm advection
gradually increasing downstream over our region through Tuesday
afternoon. The main consequence of the increasing warm advection
will be to gradually increase humidity and precipitation chances,
especially along the periphery of the CWA.
For today, have introduced slight chances of showers and storms
south and east of KY-80/Hal Rogers Parkway as an upper-level
disturbance grazes the area to the north and with increasing
moisture advection in the lower levels from the south in response to
this passing disturbance. Most likely locations to see such
convective activity will be along the higher terrain near and along
the Tennessee and Virginia borders. While other parts of the
forecast area could also see a few showers or storms, confidence is
not high enough to warrant >=15 PoPs needed for a mention in the
official forecast at this time. Will continue to watch the CAMS and
HREF and make adjustments accordingly if upstream MCS activity may
graze parts of the forecast area from the north and west.
Temperatures will once again approach or exceed record highs today,
especially as warm advection gradually increases yet overall cloud
cover and precipitation chances remain on the low side. Widespread
mid-90s are again expected, with heat indices averaging around 100
degrees.
With continued modest increases in warm advection overnight tonight,
expect warm overnight lows in the 70s, with mid to upper 60s in some
sheltered river valleys.
For Tuesday, warm advection continues to increase through the
afternoon with increasing PoPs from the northwest especially as a
cold front and lower-level jet activity begins to move into the Ohio
River Valley ahead of the large upper trough approaching the
Midwest. Nevertheless, most of the forecast area will remain hot,
dry, and mostly sunny through the afternoon, resulting in highs once
again in the mid-90s and heat indices averaging around or just a
little over 100 degrees.
.LONG TERM...(Tuesday night through Sunday)
Issued at 519 AM EDT MON JUL 15 2024
The 15/00z model suite upper level analysis beginning Tuesday
evening shows ridging retreating off the Southeast Atlantic
Seaboard and also into the Desert Southwest while a positively-
tilted trough, extending from northern Quebec southwest into the
Central Plains, dives toward the Great Lakes and Ohio Valley. At
the surface, weak low pressure is passing from the Ottawa Valley
into the Lower St. Lawrence Valley, dragging a cold front in tow.
A theta-e analysis shows that cold front approaching the Lower
Ohio River on Wednesday morning and then slowly sinking
southeastward across the Commonwealth Wednesday and Wednesday
night before stalling just to our south and east Thursday night
and Friday, as the core of the upper level trough rapidly dampens
and pulls away to the northeast. This will leave the Ohio Valley
under broad mean troughing into the upcoming weekend. Meanwhile,
the largely orphaned frontal boundary will tend to waver under
passing impulses aloft while becoming more diffuse with time.
There is not great model agreement on which impulse will trigger
the greatest coverage of deep convection, though the southeastern
counties nearer to the Virginia border will likely see the best
rain chances given the nearby remnant boundary.
Ahead of the cold front on Wednesday and early Thursday, PWATs are
expected to climb into the 2.0 to 2.2 range, well above normal for
this time of year. These PWATs combined with warm rain processes
should set the stage for torrential downpours at many locations. In
spite of the parameter space, streamflows and 0-to-100 cm soil
moistures are generally below the 25th percentile and even below the
10th percentile at a significant number of locations. These
factors as well as progressive storm motions should be a major
mitigating factor for any high water concerns. Forecaster
confidence for organized severe thunderstorms on Wednesday and
Wednesday night is currently low and will likely depend on how the
mesoscale convective activity unfolds along and ahead of the
front on Tuesday night. Low-resolution model guidance still points
to the highest PoPs being Wednesday afternoon, but that could be
undermined by significant convection that occurs earlier in the
day as hinted at by the very end of the 06z NAMNEST and HRRR runs.
As we come into the range of the full CAM suite for this event,
substantial changes to the PoP timing and values may be needed. At
any rate, the chance for rain showers and thunderstorms will tend
become more confined, though not necessarily exclusively, to the
far southeastern counties adjacent to Virginia and Tennessee from
later Thursday on through the upcoming weekend.
Temperatures will start off hot and muggy on Tuesday evening, but
should be alleviated for many locations by Wednesday afternoon as
clouds and showers bring down the temperature. Look for overnight
lows in the upper 60s to mid 70s Tuesday night followed by highs
in the mid 80s to near 90 on Wednesday. The truly cooler air
follows the front on Thursday with high temperatures only in the
upper 70s to lower 80s. As the front waffles nearby, expect
temperatures to slowly moderate such that most locations will see
highs return to the middle 80s by week's end. Nighttime lows
mainly range in the 60s after Wednesday, although a few upper 50s
cannot be ruled out in sheltered valleys on Thursday Night and
Friday morning where sufficient clearing and drying is able to
occur.
&&
.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
ISSUED AT 714 AM EDT MON JUL 15 2024
VFR conditions are expected to prevail through the TAF period,
Attention then turns to this afternoon and any potential
thunderstorm development. Currently thinking can withhold VCTS
from all TAF sites for right now, but will need to monitor model
and observed trends as there could be some upstream convection
that pushes toward KSYM much like yesterday, but most likely any
thunderstorms remain south of the TAF sites toward the TN and VA
border areas. Light and variable winds will begin to trend more
southwesterly to west-southwesterly and may increases as high as 5
to 9 kts in the afternoon, before diminishing with the loss of
daytime heating. Any possible showers and thunderstorms could
also produce gusty and erratic winds.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...VORST
SHORT TERM...CMC
LONG TERM...GEERTSON
AVIATION...CMC
Source:
JKL issues Area Forecast Discussion (AFD) at Jul 15, 11:06 AM EDT---------------
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