JKL issues Area Forecast Discussion (AFD) at Jul 26, 12:24 AM EDT915
FXUS63 KJKL 260424
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1224 AM EDT Sat Jul 26 2025
.KEY MESSAGES...
- Heat indices will approach 100 degrees in many places each day
through Tuesday, and could be in excess of 105 degrees on the
warmest days the early to middle part of next week.
- Scattered shower and thunderstorm chances return area-wide for
the upcoming weekend.
&&
.UPDATE...
Issued at 1223 AM EDT SAT JUL 26 2025
With the absence of any convection as of 04z PoPs have been
lowered to below 15 percent for the remainder of the overnight
period. A shower or storm cannot be completely ruled out, however,
within a weak warm advection regime.
With several locations forecast to possibly see heat indices approach
or reach 105 degrees later today, a Heat Advisory or Special
Weather Statement may be needed later this morning.
UPDATE Issued at 932 PM EDT FRI JUL 25 2025
Made minor refinements to PoPs and Sky grids based on latest
observed trends, and utilized the most recent hourly observations
as the initialization for the hourly grid forecast.
UPDATE Issued at 658 PM EDT FRI JUL 25 2025
Extended low-end PoPs (generally 10 to 15 percent) well into the
overnight given sufficient instability plus the GFS depicting a
weak low-level southwesterly jet developing toward sunset
providing a little bit of extra warm advection. No other changes
otherwise.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 200 PM EDT FRI JUL 25 2025
The last full work week of July is coming to a close on a hot and
humid note. Thermometers across the JKL forecast area are ranging
mostly in the upper 80s to near 90F early this afternoon. An
extensive cumulus field has also developed, with a few of the more
robust towering cumulus maturing enough to produce small showers
or pin-prick sprinkles. The latest analysis shows a nearly
stationary cold front extending from the Canadian Maritimes
southwest over/near Lake Ontario and Erie and beyond into central
Missouri. Surface high pressure is centered northeast of the
Bahamas but continues to exert its calming influence into
southeastern Kentucky. The surface high is mirrored aloft by a
~596 dam high centered just a bit further northwest along the
South Carolina Coast. Broad, low amplitude ridging extends
northwest from the high across the heart of the nation, though a
vigorous vorticity max and shallow shortwave trough is noted over
the Central Plains.
Through the short-term period, the aforementioned disturbance
will ride east northeast and over the ~596 dam high while the high
itself retrogrades westward to near/over northern Georgia. A weak
wave of low pressure under the disturbance will track toward Lake
Erie and cause the stalled boundary to lift back north as a warm
front. Southerly return flow on the west side of the high (and in
the lows warm sector) will cause PWATs to continue rising into the
1.6 to 1.8 inch range by this evening, and then flirt with 2.0
inches for Saturday and Saturday night. Though the air mass will
be quite juicy, the only forcing mechanisms through Saturday night
appear to be weak upper-level perturbations riding around the 500
hPa high as well as strong differential surface heating. RAP13
MLCAPE values only peak in the 1,000 to 2,250 J/kg range today and
in the 1,500 to 2,500 J/kg range on Saturday. Weak mid-level
lapse rates and shear, as well as abundant mid-level dry air, are
likely to suppress updraft vigor. However, that dry mid-level air
does suggest that if a stronger storm core somehow developed,
there would be a chance of a downburst. Any deep convection could
produce a briefly torrential downpour, but the disorganized/scattered
nature of the convection would not suggest any substantial hydro
concerns at this time. Convective coverage is likely to peak each
afternoon and early evening, coincident with peak diurnal
destabilization, and be a little more widespread on Saturday.
However, an isolated shower or storm cannot be entirely ruled out
at other times of the day.
In sensible terms, look for hot and humid conditions to continue,
with afternoon high temperatures within a few degrees of 90F
while nighttime lows range in the lower to middle 70s. Dew points
in the lower to middle 70s will combine with those hot air
temperatures to produce maximum heat indices in the upper 90s to
lower 100s at most locations. There will also be isolated to
scattered thunderstorms each afternoon and evening. Nights and
mornings should be dry for most, if not all, of the area, but a
stray shower or storm still cannot be ruled out entirely during
those times.
.LONG TERM...(Sunday through Friday)
Issued at 459 PM EDT FRI JUL 25 2025
Our most dominant feature through most of the long term period will
be an upper level high which will start out in the vicinity of GA
on Sunday. It is expected to shift/build westward with time,
becoming most prominent over the lower/middle Mississippi Valley
by Tuesday. Although we will not be directly under the high, it's
proximity will give us hot and humid conditions and very weak
flow aloft. Models also suggest that enough heat and humidity
will be present to fuel area of showers/thunderstorms around the
high, especially it's periphery. However, with weak flow aloft
there would be very little movement of any showers/thunderstorms
for our area through early in the week, limiting their coverage,
with much of our local daily activity likely due to subsequent
development along outflows after initial development.
The upper high should weaken mid to late week, while the upper
level prevailing westerlies on the north side buckle and develop a
trough over southeast Canada and the northeast CONUS and a ridge
to the west. This would aid a surface cold front to move
southward and make it through our area. While both the GFS and
ECMWF show this, there is still some model to model and run to
run inconsistency on the timing and how far south the front goes.
At this point, the likely fropa timing for our area is in the
neighborhood of Wednesday night or Thursday. Along with the fropa
would come an increased POP, followed by drier weather with at
least some relief from heat and humidity late week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
ISSUED AT 715 PM EDT FRI JUL 25 2025
VFR conditions are expected to generally prevail through the
period at the TAF sites. Isolated to widely scattered showers and
a thunderstorm or two will remain possible through the overnight
with weak warm advection continuing with the development of a weak
low-level southwesterly jet. Fog is forecast to develop again in
the river valleys into Saturday morning, but confidence is too low
again to mention in any TAFs.
PROB30 groups have been included at all terminals beginning
between 15z and 18z, with scattered showers and storms expected
from midday through early Saturday evening.
Winds will remain variable to southwesterly around 7 kts or less
thanks to high pressure east of the region.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...CMC
SHORT TERM...GEERTSON
LONG TERM...HAL
AVIATION...CMC
Source:
JKL issues Area Forecast Discussion (AFD) at Jul 26, 12:24 AM EDT---------------
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