JKL issues Area Forecast Discussion (AFD) at Sep 29, 5:02 PM EDT553
FXUS63 KJKL 292102 CCA
AFDJKL
AREA FORECAST DISCUSSION...CORRECTED
National Weather Service Jackson KY
502 PM EDT Sun Sep 29 2024
.KEY MESSAGES...
- There will be persistent showers around, at times, until a cold
front passes through on Tuesday night.
- Dry weather arrives behind the cold front for Wednesday and
then lasts through the end of the week.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 500 PM EDT SUN SEP 29 2024
The persistent low pressure system bringing us clouds and rain in
the wake of Helene's remnants still lingers. The surface system
has practically dissipated, but a weakening mid/upper level
closed low remains centered over KY. Clouds have limited our
heating and destabilization, but there's been enough for small,
spotty showers to regenerate this afternoon. A slow decline in
activity is expected this evening, but the potential probably
won't completely go away tonight.
With the upper low continuing to weaken, it will further open up
and get absorbed back into progressive flow aloft, especially as a
potent trough approaches the Great Lakes from the west northwest
on Monday and Monday night. However, before it leaves, it looks
like limited warming will cause another uptick in showers over our
area on the west side of the low on Monday, and mainly 40-60% POP
has been used. The POP drops off considerably on Monday night as
heating is lost and the low departs further to the east.
Thunder has been kept out of the short term forecast. Although
convection will occur, forecast soundings in both the NAM and GFS
suggest it will remain capped in the mid levels, with the top of
the convection remaining warmer than -20C.
.LONG TERM...(Tuesday through Sunday)
Issued at 500 PM EDT SUN SEP 29 2024
The long term forecast period begins with a pattern flip, as the low
pressure remnants of historic Hurricane Helene will finally depart
the area on Tuesday. A few showers associated with said remnants may
linger through the AM hours, but the main trigger for Tuesday's
shower chances will be an approaching cold front from the Northwest.
On the backside of the departing upper low, flow throughout the
column will turn towards westerly and northwesterly orientations.
This will advect dry air into portions of the column, meaning that
the front will mostly be working with antecedent moisture. NAM and
GFS forecast point soundings continue to depict a capping inversion
on Tuesday afternoon and evening, and thus the instability
associated with this system looks questionable. Along these lines,
the timing of this FROPA looks unlikely to align with peak diurnal
heating, which will be relegated by antecedent cloud coverage
anyways. LREF probabilistic ensemble guidance accordingly suggests a
less than 20% of greater than or equal to 500 J/kg of CAPE during
this period, and the chances for organized thunderstorm activity
appear minimal. The NBM is likely too aggressive with the thunder
chances in the grids, and these have been decreased as a result.
Expect any rain on Tuesday and Tuesday night to fall in the form of
generic showers. High temperatures will be in the mid 70s, and the
passage of this front overnight will allow lows to drop down towards
the 50s, especially in the Bluegrass region.
After this, ridging looks to finally build back into the area on
Wednesday and put an end to these dreary and damp conditions. With
dry air advection and synoptic scale support for subsidence, expect
the sun to come back out. Forecast guidance collectively agrees that
this ridging and associated surface high pressure will remain in
place through the end of the work week. This will allow noticeable
ridge-valley thermal splits to re-enter the forecast grids for the
first time in a while. Diurnal temperature ranges will also widen in
this new pattern, with afternoon highs incrementally creeping up
from the low 70s on Wednesday towards 80 on Friday. Overnight lows
in the 50s will be close enough to forecast dew points to support
the formation of patchy valley fog early each morning, especially
near sources of water and in particularly sheltered places.
On Friday night into Saturday, a secondary cold front looks to
approach the Ohio River Valley. This boundary will be associated
with upper level troughing further in the Great Lakes region, but
this particular-set up does not look particularly impactful when it
comes to precipitation. With limited moisture return and displaced
dynamic support, PoPs will be relegated to below 20% through the end
of the period. There may be a subtle increase in cloud coverage on
Friday night, but the primary effect of this second frontal passage
will be the reduction of high temperatures. Given the trend towards
drier weather, afternoon highs have been slightly increased this
weekend, but remain at a seasonably appropriate 75 degrees under
mostly clear skies. Lows will likely dip down into the mid to upper
40s in the post frontal, modified continental polar airmass. This
will be a welcome change from the wet weather of the past week, and
thus this particular long term forecast package is defined by a
return to classic fall conditions across the Commonwealth.
&&
.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
ISSUED AT 750 AM EDT SUN SEP 29 2024
Conditions at the terminals across the area, currently are highly
variable - fluctuating between VFR/MVFR/IFR as additional rain
bands continue to move generally north through eastern Kentucky.
With these bands of showers, deteriorating categories and lowered
VIS can be expected, for a time. The showers will gradually
start to decrease in coverage by late morning, this shift will
probably lead to improvements in both CIG and VIS. Look for
conditions to deteriorate later tonight, though, as clouds descend
and fog develops. Light and variable winds are expected to hold
through the period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HAL
LONG TERM...MARCUS
AVIATION...GREIF
Source:
JKL issues Area Forecast Discussion (AFD) at Sep 29, 5:02 PM EDT---------------
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