JKL issues Area Forecast Discussion (AFD) at Oct 20, 3:26 PM EDT568
FXUS63 KJKL 201926
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
326 PM EDT Sun Oct 20 2024
.KEY MESSAGES...
- Dry weather is forecast for the week.
- A warming trend will last through Wednesday, followed by a
modest drop in temperatures behind a cold front late in the
week.
&&
.UPDATE...
Issued at 1046 AM EDT SUN OCT 20 2024
Have blended observed morning temperatures and dew points into the
forecast, and made adjustments for a faster drop in eastern
valley temperatures this evening.
UPDATE Issued at 650 AM EDT SUN OCT 20 2024
No big changes to the forecast with just the inclusion of the
latest obs and trends for the T/Td/Sky grids with this update.
These minor adjustments have been sent to the NDFD and web
servers.
&&
.SHORT TERM...(Today through Monday)
Issued at 425 AM EDT SUN OCT 20 2024
07Z sfc analysis shows high pressure holding over eastern Kentucky
again keeping the skies clear and winds light overnight. These
are excellent conditions for radiational cooling and have
resulted in a moderate to large ridge and valley temperature
difference through the night. Specifically, readings currently
vary from the lower 50s on the hills to the upper 30s in a few of
the deeper valleys. Meanwhile, dewpoints are running in the mid
30s to lower 40s, most places. This air mass is still not dry
enough to keep all the fog at bay with evidence of it seen in the
southeast river valleys via the latest satellite images.
The models, and their individual ensemble suites, continue to be
in excellent agreement aloft through the short term portion of the
forecast. They all depict ridging from the southwest at 5h
spreading over the lower Ohio Valley through Monday. The high
heights from the ridge's influence will mitigate any effect from
some energy at mid levels that drops south through eastern
Kentucky tonight. This occurs ahead of an approaching trough
moving out of the Central Plains toward the Ohio Valley late in
the period. The small model spread again supported using the NBM
solution as the starting point for the grids though with
some substantial adjustments for more terrain distinctions in
temperatures early this morning and again tonight.
Sensible weather features a persistent, dry and quiet forecast
through the start of the new work week with light winds and
mostly clear skies. This means a large diurnal curve for the JKL
CWA with highs reaching the low to mid 70s today and even warmer
on Monday. Again we can expect deeper mixing than modeled to
result in dry air filtering down to the sfc and making for lower
dewpoints than represented by the NBM today and again Monday
afternoon. At night, look for another round of excellent
radiational cooling conditions yielding more moderate to large
ridge and valley temperature splits into Monday morning. Valley
fog will again be pronounced late tonight into early Monday with
locally dense patches found near bodies of water. Again cannot
rule out some patchy frost in a few places both through dawn this
morning and late tonight.
The changes to the NBM starting point mainly consisted of adjusting
the hourly T grids for more terrain distinction and a faster
valley drop off after dark along with drier afternoon dewpoints
and humidities. As for PoPs: kept them about zero through Monday
- in line with the NBM and all guidance.
.LONG TERM...(Tuesday through Sunday)
Issued at 325 PM EDT SUN OCT 20 2024
The benign weather continues well into the extended period of the
forecast. The interesting part of this is that the upper levels are
actually quite active during this time. By Tuesday, upper level
ridging will give way to quickly decreasing heights and a closed
upper level low moving towards the Ohio Valley. It will weaken to an
open wave throughout the day, traversing Kentucky during the evening
and first part of the overnight hours. From here, a much stronger
upper level trough will pass across the Ohio Valley through
Wednesday, followed by a shortwave on Thursday as overall flow
becomes more zonal. According to the ECMWF, another shortwave will
pass through Kentucky on Friday, with unsettled WNW flow continuing
through the day Saturday as well. By Sunday models lose agreement,
with the ECMWF showing ridging building in the, and the GFS holding
on the unsettled WNW flow pattern.
So how does Kentucky manage to stay dry during this entire time?
Amazingly enough, it's at the surface. Surface high pressure will
remain across the CWA in some shape or form throughout the entire
extended, despite the upper level pattern changes. When the first
weakening closed low moves through, high pressure will hold tight
across much of Kentucky, specifically eastern KY. When that finally
exits eastward, another round of surface high pressure will move in
from the NW by Wednesday evening.
Models do finally show a breakdown in the surface pattern by Friday.
The center of Wednesday evening's high pressure will have pushed
eastward across the Ohio Valley and Kentucky, exiting to the east by
Friday morning. This will allow yet another shortwave and surface
low pressure system to develop and even produce some precipitation
across the Middle and Upper Mississippi Valley. Given the lack
strength in this system, and no real airmass change, the system will
be somewhat weak and limited for precip coverage. That being said,
both the GFS and ECMWF do show at least some of the precip making it
into eastern Kentucky by Friday evening, with more isolated pops
continuing through Saturday. Currently, the NBM does bring in some
14% pops during this time, which is just below isolated wording.
Given how far out in the period it is, don't have enough confidence
to increase the pops just yet to include isolated wording, but will
be interested to see if trend continues and makes it into the next
NBM run. Either way, by that point we will need the rain, but don't
expect it's impacts to be that impressive.
Daytime temperatures will be well above normal for Tuesday and
Wednesday given the sharper SW flow advecting warmer air into the
region. A dry cold front is then forecast to move through late
Wednesday into Thursday morning, as the shortwave exits the region
and gives way to more WNW flow. This will cool things down again.
Highs on Thursday will be in the 60s, some 10 to 15 degrees less
than Wednesday. With high pressure passing overhead of eastern KY by
Thursday night, this will also be our coolest night, with lows in
the 30s. A warming trend is expected after this point, as return
flow on the backside of the exiting high will allow for another
boost of SW flow into the region, followed by the approaching weak
low pressure system.
&&
.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
ISSUED AT 705 AM EDT SUN OCT 20 2024
VFR conditions prevail through the TAF period with light and
variable winds. Valley fog will be around for another hour or so
this morning and again late tonight. This may be dense for brief
periods of time leading to localized VLIFR conditions however
these low visibility conditions are not expected to affect any
TAF terminals for more than a fleeting amount of time.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...HAL/GREIF
SHORT TERM...GREIF
LONG TERM...JMW
AVIATION...GREIF
Source:
JKL issues Area Forecast Discussion (AFD) at Oct 20, 3:26 PM EDT---------------
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