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297
FXUS63 KJKL 021450
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1050 AM EDT Thu May 2 2024

.KEY MESSAGES...

- Very warm with record or near-record highs this afternoon.

- Shower and thunderstorm chances return to the forecast Friday
  through Wednesday.

- Cooler this weekend with highs generally near 80 before turning
  very warm again by the middle of next week.

&&

.UPDATE...
-- Changed Discussion --
Issued at 1050 AM EDT THU MAY 2 2024

No real changes needed for the late morning update, except to
blend in hourly observations into the forecast.
-- End Changed Discussion --

&&

.SHORT TERM...(Today through Friday)
Issued at 335 AM EDT THU MAY 2 2024

Satellite imagery as of this writing is beginning to show some fog
developing in the river valleys. This trend is anticipated to
continue until sunrise. Fog will not be nearly as widespread as it
was 24 hours ago. This, as we were able to mix out on Wednesday and
evaporate some of Tuesday`s rainfall.

Very warm this afternoon with near-record high temperatures. Some
spots could hit 90 degrees; this first 90-degree temperature would
be about 6 weeks ahead of average (at Jackson). Meanwhile, the
forecast high of 88 would break the record set in 2012 by 1 degree.
A high of 88 is near the climate record`s average first 88 degree
date. This heat is thanks to a towering 579dm ridge centered over the
Florida Peninsula. By Friday, this ridge gives way to an approaching
trough, currently over the Central Plains. Expect increasing clouds
late Thursday night and the chance of showers and thunderstorms
increasing after sunrise Friday. Instability is meager and upper-
level support is poor. Therefore, showers and any thunderstorms will
be rather disorganized Friday.

A word about the coming night`s low temperatures: Current forecast
lows are the coldest among model guidance with a forecast-area
average low of about 59 degrees. A 25th percentile forecast could be
closer to 62 degrees. Prior to clouds arriving, lows could quickly
drop towards dew points that will be in the 50s. However, should
cloud cover arrive quickly after sunset our existing forecast lows
would be too cold. I`ll pass this concern along to the incoming
shift for consideration.

.LONG TERM...(Friday night through Wednesday)
Issued at 425 AM EDT THU MAY 2 2024

After a period of relatively dry and quiet weather during the last
few weeks, the weather pattern will become rather humid and
unsettled for this upcoming weekend and next week. The 02/00z
model suite analysis beginning Friday evening shows a departing
upper level ridge extending from the Outer Banks northward into
Quebec. To our northwest, an upper level trough, associated with
an ~540 dam parent low over northwest Ontario, is traversing the
Northern Plains. Another deeper ~534 dam low is approaching the
Pacific Northwest. At the surface, an occluding ~1002 mb low is
wrapping up over northwest Ontario. The occluded front extends to
near a triple point low over the Eastern Great Lakes and from
that low a cold front trails southwestward to along the Lower
Ohio River and beyond into the Ozarks. A secondary cold front
extends from northwestern Ontario down through the Upper Midwest
and Central Plains.

With weak flow aloft and marginal instability, expect convection to
be more of a disorganized nature through Sunday. Kicking off
Friday evening, the CAMS suggest disorganized convection
transiting much of eastern Kentucky ahead of the first front on
Friday evening and night. The 00z HRRR suggests there could be a
weak MCV which could make the weather a little more interesting
should it occur, but not placing much confidence in that solution
at this point as it is at the very end of the CAM range.
Rather, anticipate that convection will wane late Friday night
and early Saturday morning as the first cold front becomes diffuse
and washes out over the Lower Ohio Valley. Subtle disturbances
embedded in the southwest flow aloft are then expected to spark
off additional convection (70-80 PoP) during the day on Saturday,
largely coincident with peak heating. The secondary cold front
then drifts to near the Lower Ohio River and stalls on Sunday
while another disturbance passes overhead, again likely supporting
another round of convection (60-70 PoP).

Heading into the new work week, the upper level ridge to our east
will have shifted off the East Coast while the Pacific northwest
closed low will eject out on the Central/Northern Plains on Monday
and then slowly meander northeastward while weakening through
mid-week. Initially, this system will foster a strong lee-side
low (likely sub-980 mb) over the northern High Plains on Monday
and Tuesday until the system occludes, after which the triple
point will become the primary surface low over the Upper
Midwest/Upper Great Lakes/Ontario on Wednesday. The increasing
warm conveyor belt feeding into the initial lee-side low and then
the triple point low will begin pulling increasing warmth and
humidity back northward across the Ohio Valley, leading to
increasing amounts of shear and instability each consecutive day
through Wednesday. At the same time, there will be triggers
(additional upper level disturbances) passing over the Ohio Valley
favoring additional convection, particularly during the afternoon
and evening hours coincident with peak heating. The increasingly
favorable shear and instability point to a rising threat for
organized storms and severe weather as we head deeper into the
week. Additionally, while there is not yet an apparent substantial
flooding risk, PWATs flirting with or exceeding the 90th
percentile, relative to climo, and generally slow cell motions for
the first several days may begin to saturate soils and increase
streamflows over time. This may eventually lead to isolated high
water concerns at any location that receives repeated downpours
over a period of several days.

From a more sensible perspective, the weather will turn noticeably
more humid and at times unsettled over the long-term. While the
upcoming weekend shouldn`t be a complete washout, those with outdoor
activities planned will probably want to have an umbrella or
shelter available for those times when showers or garden-variety
thunderstorms do occur. Temperatures will remain on the mild side
of normal throughout the weekend with highs in the mid 70s to
lower 80s on Saturday and in the upper 70s to mid 80s on Sunday.
Looking ahead to the new work week, those daily shower and
thunderstorm chances will continue, highest during the afternoon
and evening hours. Any thunderstorms will also have the potential
to become more intense with each passing afternoon, such that all
severe hazards are a concern by Wednesday. Forecast high temperatures
also trend warmer each day, reaching the mid to upper 80s by
Wednesday. Cloud cover and high humidity levels should help
minimize nocturnal ridge-valley temperature splits, keeping
nighttime minimum temperatures mostly in the upper 50s to lower
60s in valleys and lower to middle 60s elsewhere.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
ISSUED AT 634 AM EDT THU MAY 2 2024

Amid high pressure in place, existing TAFs were generally in good
shape. Fog has developed in the river valleys, per satellite, but
TAF sites have not been impacted. Therefore, any previous fog
mention was removed. Beyond 3z, high BKN to OVC skies are favored
to spread in over KSME and KLOZ. Showers and thunderstorms
approach those same sites from the west after 12z Friday.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...CMC
SHORT TERM...BROWN
LONG TERM...GEERTSON
AVIATION...BROWN