JKL issues Area Forecast Discussion (AFD) at Jul 27, 7:38 AM EDT224
FXUS63 KJKL 271138
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
738 AM EDT Sat Jul 27 2024
.KEY MESSAGES...
- Mainly dry weather is expected today.
- There is an increasing threat for excessive rainfall from
multiple rounds of showers and thunderstorms Sunday through
Tuesday, which may lead to a flooding potential. A lesser
probability of showers and thunderstorms will extend through
late week.
&&
.UPDATE...
Issued at 738 AM EDT SAT JUL 27 2024
The forecast is in good shape, with the only updates being to
blend in early morning observed temps and dew points.
&&
.SHORT TERM...(Today through Sunday)
Issued at 529 AM EDT SAT JUL 27 2024
Upper level ridging is present from the upper Great Lakes
southward over the southeast CONUS early this morning, while
surface high pressure is centered near the lower Great Lakes. The
surface high has brought a somewhat cool and dry air mass (by mid
summer standards) into northeast KY. The front at the leading edge
of the air mass has dropped well to our southwest in TN, but dew
points increase from northeast to southwest in KY as you get
closer to the boundary. The air should be dry enough to preclude
showers/thunderstorms in our area today, but they may be close to
our southwest this afternoon.
An upper level low currently centered over eastern OK will move
north northeast to the upper Mississippi Valley by late Sunday.
Troughing extending south from the low will approach our area from
the west. As this happens, we will have deep moisture advect over
our area. This will bring a return of showers/thunderstorms on
Sunday, especially for our western counties.
.LONG TERM...(Sunday night through Friday)
Issued at 336 AM EDT SAT JUL 27 2024
Upper level troughing will be the name of the game throughout the
extended period for eastern KY. A strong upper level low will be
present across the Atlantic Seaboard on Sunday. A second incoming
trough will begin to impact the Ohio Valley from the west by Sunday
evening, quickly merging with the stronger system to the east by the
start of the extended period Sunday night into Monday morning. This
upper level low is expected to slowly shift northward into New
England through mid-week, but will leave much of the eastern Conus
in a deep troughing pattern as a result. This pattern also leaves
much of the region vulnerable to additional shortwaves passing
through during this time.
Meanwhile, a strong area of ridging will be in place across the far
south-central portion of the Conus through much of the week. Models
do try to show some of this ridging finally spreading its way into
the southeast, including rising heights across Kentucky, for
Thursday, but our location on the northern fringes likely won't be
enough to stop waves of energy from moving through much of the Ohio
Valley during this time. Models then show the upper level troughing
re-establishing its hold across the eastern Conus once more,
resulting in lowering heights once more and the return of a more
active pattern for Friday and heading into the weekend.
Given the trough set up through the majority of the period, and
eastern KY's general location on the SW flow side, it's not a
surprise that SW flow will descends all the way to the surface and
persists through much of the extended period. This will result in
two things - moisture and heat. Not expecting any large-scale
airmass changes or frontal boundaries during this pattern, so hot
and humid conditions with increased moisture and instability will be
the name of the game. Shower and thunderstorm chances are on tap
nearly every day. Even Thursday into Friday, as heights rise some
across the region, we will still not be immune to some instability
and generally diurnally driven convection during the afternoon.
Monday will be the coolest day according to the NBM, with temps
maxing out in the low 80s. This is also likely one of our wettest
days, with abundant cloud cover/rainfall inhibiting higher
temperatures. But once the SW flow regime sets up and precip
chances lesson, expect temperature to trend higher, topping out
in the upper 80s to around 90 by mid-week, persisting into the
weekend. Humidity will make it feel somewhere between the mid 90s
and 100 degrees during this time.
In addition, as mentioned before, there will be daily chances for
showers and thunderstorms. Did not have enough confidence to deviate
away from the NBM pops at this point, but did try to peak them
during the afternoon when instability and lift will be their
highest, without the presence of a passing boundary. WPC has placed
much of the JKL CWA in a slight risk for excessive rainfall from 12Z
Sunday through 12Z Wednesday. Their main concern is the increased
precipitable water which could lead to heavy downpours and multiple
storms moving over the same location. That being said, much of
eastern KY has received very little rainfall over the past month,
with a few exceptions, so most locations should be able to handle
decent rainfalls. There isn't a very defined boundary setting up for
which these storms will likely train, though can't rule out that if
storms do develop and move over the same location with heavy rain
rates/amounts, this could lead to some isolated concerns. Will
continue to monitor this as we get closer to time, but right now
confidence isn't very high in a widespread flash flood concern.
Meanwhile, SPC has eastern KY in a general thunderstorm risk
throughout the period, again without lack of forcing. Generally
expect diurnally driven pulsy showers and storms.
Finally, given the clouds and moisture in place, and without the
presence of a high pressure system moving overhead (subsidence),
chose not to include any ridge/valley splits for temperatures during
the extended period. There could be moments of clearing in the
clouds overnight, especially late in the week, which may result in
temperature drops. However, confidence on when and where this would
happen is quite low, so just kept with the modeled temperatures at
this time. Will make tweaks with future forecasts as we get closer
to that period. The same goes for fog as well. It is likely with so
much moisture that we could see some fog overnight in places, but
exactly when and where this will set up is unknown, and may not be
confined to just the valley locations.
&&
.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
ISSUED AT 738 AM EDT SAT JUL 27 2024
Late night and early morning fog will affect many valley
locations with IFR or worse conditions, but will likely avoid TAF
sites during the period. Otherwise, VFR conditions and light
winds are forecast.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...HAL
SHORT TERM...HAL
LONG TERM...JMW
AVIATION...HAL
Source:
JKL issues Area Forecast Discussion (AFD) at Jul 27, 7:38 AM EDT---------------
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