JKL issues Area Forecast Discussion (AFD) at Sep 15, 7:25 PM EDT120
FXUS63 KJKL 152325
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
725 PM EDT Sun Sep 15 2024
.KEY MESSAGES...
- After high temperatures well into the 80s in most places this
weekend, a slight cool-down arrives for the start of the new
work week.
- Dry weather lasts through Monday afternoon, followed by a
potential for showers arriving east to west Monday night into
Tuesday. Additional shower (and possible thunderstorm) chances
will occur through midweek.
&&
.UPDATE...
Issued at 725 PM EDT SUN SEP 15 2024
Early evening obs have been blended into the forecast without any
substantive changes.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 420 PM EDT SUN SEP 15 2024
19Z sfc analysis shows high pressure still off to the northeast
of Kentucky while low pressure is weakening to the southwest. This
is maintaining a dry downsloping flow of low level air into this
part of the state making for lower humidities and warmer
temperatures. Accordingly, readings have hit the low to mid 80s
through the JKL CWA while dewpoints, amid mostly sunny skies and
southeast to east winds of 5 to 10 mph, vary from the lower 50s
northeast to the lower 60s in the southwest.
The models, and their individual ensemble suites, are in pretty
good agreement aloft through the short term portion of the
forecast. They all depict a weakening rex block in place over the
eastern half of the nation. Lower 5h heights to the southwest of
Kentucky and higher ones northeast is promoting anomalous
southeasterly mid level flow overhead at the start of the period
through Monday before becoming light and variable into Tuesday
morning while the eastern/coastal portion of the upper low drifts
into the Southern Appalachians. This flow will sustain a stream
of weak impulses moving through aloft but into an airmass too dry
to exhibit much more than some high clouds through Monday
afternoon. A stronger element then retrogrades into the area from
the Carolinas that night bringing some deeper moisture along with
it. On account of the very small model spread through the short
term portion of the forecast, have favored the NBM as the starting
point for the grids with little adjustment needed aside from
incorporating more terrain detail into the temperatures for the
entire area tonight and the first part of Monday night in mainly
the west portion of the JKL CWA before the clouds thicken up. Did
also include the latest CAMs guidance for the showers of Monday
night.
Sensible weather features another mostly clear night with good
radiational cooling and the resultant ridge to valley terrain
differences in temperature. Fog should be confined to just near
the rivers late tonight given the dryness of the air. Look for
more clouds to arrive Monday morning from east to west and
thicken up with time. This will set up a high temperature
gradient across eastern Kentucky with low 80s east and mid 80s
west. The clouds fill in Monday evening with a chance of showers
arriving to our far east from the SE coastal system working west
into, and across, the Southern Appalachians. Stable conditions
should keep the thunder threat to a minimal with this rain - which
is needed for most of the area - though best chances will probably
remain in the east into Tuesday.
The changes to the NBM starting point mainly consisted of adding
in more terrain distinctions for temperatures tonight. Dewpoints
were dropped back on Monday afternoon closer to the NBM 5 percent
values. PoPs were enhanced on Monday night with the latest
guidance from the CAMs.
.LONG TERM...(Tuesday through Sunday)
Issued at 500 PM EDT SUN SEP 15 2024
A weakening rex-block pattern is in place over the eastern CONUS at
the start of the long-term period. The 15/12z 500H model suite
analysis beginning Tuesday morning shows an ~580 dam low (perhaps
subtropical/tropical) centered over or adjacent to the Southern
Appalachians. A blocking high is found over the Western Atlantic
while an associated ridge axis extends westward over the Southern
New England to the Eastern and Southern Great Lakes where it
separated by a col from another ridge axis over the Southern and
Central Plains. A longwave trough is analyzed further upstream
over the CONUS over/west of the Rockies. At the surface, a weak
low is found near or just east of the Southern Appalachians while
a more robust ~1025 mb high is stationed further north over/off
the coast of New England.
The blocky pattern changes only slowly during the long-term. In
general, the upper low and its surface low only gradually drift
northwest through midweek. Cyclonic flow around the high will
cause deep moisture (PWATs rising to between 1.3 and 1.5 inches)
to move into eastern Kentucky on Tuesday and linger into Thursday.
For the late week and the weekend, the upper low transitions into
an eastward translating open wave as subsequent high amplitude
ridging builds across the Mid-Mississippi Valley, Lower Ohio
Valley, Great Lakes, and Quebec. This will set the stage for drier
weather to return as a robust surface high brushes the Eastern
Kentucky Coalfields to the north and east.
In sensible terms, plentiful cloud cover, especially east of
Escarpment, should keep temperatures in check on Tuesday, holding
high temperatures in the middle 70s at most locations, though a
few upper to around 80 cannot be ruled out over the Bluegrass and
west of I-75. With the return of deeper moisture will also come
the threat of rain (PoPs currently range from 20 west to 40 east
on Tuesday and Wednesday). The CAM solutions increasingly favor
this system reaching and spreading bands of rain across eastern
Kentucky. If these solutions hold, a marked PoP increase is likely
warranted for Tuesday and probably Wednesday in later forecast
packages. A rumble of thunder cannot be ruled out on either
Wednesday or Thursday though modeled instability is very limited.
The threat for rain diminishes on Thursday as the deeper moisture
departs. Warmer and drier weather is then on tap for Friday and
upcoming weekend as high pressure returns. Look for high
temperatures to linger mainly in the 70s on Wednesday before
moderating the near 80 for most locations on Thursday and back
into the lower 80s for most locations from Friday through Sunday.
Nighttime lows are forecast to range in the mid 50s to lower 60s
through the period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 634 PM EDT SUN SEP 15 2024
Aside from localized late night/early morning valley fog with IFR
or worse conditions, VFR conditions will prevail. Fog should not
affect TAF sites. Winds will be less than 10 kts, mostly from the
east.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...HAL
SHORT TERM...GREIF
LONG TERM...GEERTSON
AVIATION...HAL
Source:
JKL issues Area Forecast Discussion (AFD) at Sep 15, 7:25 PM EDT---------------
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