149
FXUS63 KJKL 251958
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
358 PM EDT Tue Jun 25 2024

.KEY MESSAGES...

- Heat and humidity returns for today and Wednesday.

- Next best chance of rain will be Wednesday into Wednesday
  evening.

- Hotter weather is expected to make a comeback by Friday and
  especially Saturday, with afternoon highs in the low to mid 90s
  and heat index values peaking around or in excess of 100
  degrees.

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 358 PM EDT TUE JUN 25 2024

Current surface analysis is rather active but synoptically surface
high pressure is situated over the region. Mesoscale wise, an MCS,
from last night`s activity in the Upper Great Lakes, is continuing
to dive south-southeast toward the CWA. Dry air over the region is
causing the MCS to weaken as it approaches the CWA but a shower or
two my clip areas along and north of I-64. Those showers and storms
will linger over the next couple of hours before a brief lull in
activity is expected for a few hours this evening. Then CAMs try to
bring another round of showers and storms to the area as the western
half of the current MCS tries to dive southeast into the region
after 03Z and lingering through the early morning hours of Wednesday.

Wednesday brings about another round of showers and storms. A couple
small shortwave perturbations are revolving around a parent trough
that will bring a surface low across southern Canada and a cold
front through the CWA during the day Wednesday. The SPC has placed
areas along and north of the Mountain Parkway in a Slight Risk of
severe weather. The rest of the area is under a Marginal Risk of
severe weather for cold frontal passage Wednesday afternoon. The
timing of the boundary will allow for the best instability building.
This is shown in forecast soundings as there`s decent forecast
severe weather indices in place across the area. Steep low and mid
level lapse rates are in place, instability ranging from 2,000 to
2,500 J/kg of CAPE in the afternoon is favorable, PW`s around 1.80"
(which if materialized could bring some heavy rainfall) even from
yesterday`s soundings, effective bulk shear has increased slightly
across the region which could help promote some longer-lived
stronger storms Wednesday afternoon. The biggest threat of the day
appears to be damaging wind, but large hail and possibly an isolated
tornado cannot be ruled out. However, the potential for increased
cloud cover Wednesday morning could limit the ability to build in
the best instability which alone could limit the coverage of the
thunderstorms. Thunderstorms will taper off from northwest to
southeast through the overnight Wednesday but an H850 shortwave is
forecast to develop with a surface feature riding along the
departing cold front. This secondary surface feature will keep
lingering shower and thunderstorm chances across the far eastern
third of the CWA through the end of the period.

Overall, the entire period will be highlighted by multiple rounds of
showers and thunderstorms with high temperatures remaining in the
mid-80s to low-90s and overnight lows in the upper-60s to mid-70s.

.LONG TERM...(Wednesday night through Monday)
Issued at 500 PM EDT TUE JUN 25 2024

The 25/00z model suite 500H analysis beginning Wednesday evening
shows troughing over eastern North America associated with a parent
~534 dam low spinning over southern Baffin Island. At the surface, a
cold front extends from a low over the Labrador Sea southward to
along the New England Coast and then southwestward across the
Appalachians to near the mid and lower main stem Ohio River. To
the west, an ~595 dam high is found over the New Mexico/Mexico
border and an associated ridge axis extends northward along the
eastern slopes of the Rockies to an ~571 dam high over the upper
Yukon River basin. Surface high pressure is centered over the
Upper Midwest but extends from the Central Plains all the way into
the Mackenzie River basin of Northern Canada. Another ~560 dam
low is coming ashore the Pacific Northwest.

The axis of the upper level trough will pass through eastern
Kentucky on Wednesday evening, nudging the cold front through before
it hangs up just off to our south and east on Thursday. PoPs wane
from northwest to southeast behind the front as drier and somewhat
cooler air arrives on northerly winds. By Thursday, the ridging
aloft moves in from the west while subsiding ahead of the Pacific
Northwest low/trough. At the surface, high pressure passes through
the Great Lakes on Thursday and Thursday night. As that high departs
through the Northeast on Friday, mild and moist southerly flow
redevelops over the Ohio Valley. There is a small chance for deep
convection on both Thursday and Friday, primarily over and near the
high terrain adjacent to Virginia border. PWATs continue rising
heading into Saturday and Saturday night, potentially peaking around
2.0 inches (near climatological maximums for this time of year).
With 850 mb temperatures climbing to between 20-22C on Saturday and
those anomalously high PWATs, expect dew points to rise in the 70s
coincident with air temperatures well into the 90s. This will set
the stage for heat indices approaching 105F -- advisory criteria --
at some locations. There is a better chance (30-40%) for deep
convection on Saturday, particularly over the southeastern high
terrain, though neutral to weak height rises should temper overall
storm coverage and updraft intensity. In the meantime, a low
pressure system develops over eastern Wyoming/Montana (ahead of the
Pacific upper low) before trekking across the Upper Great Lakes on
Friday night and over eastern Canada this weekend. This low will
drag another cool front through eastern Kentucky on Sunday and
Sunday night. This will bring more widespread rain chances for the
second half of the weekend. Another high pressure builds across the
Great Lakes on Monday behind the cool front, bringing a briefly
cooler and drier air mass before the heat returns again as
Independence Day approaches.

This weather pattern may bring on deja vu for some as multiple weak
cool fronts will bring the opportunity for some rainfall, followed
by a day a cooler and drier weather before heat and humidity quickly
return on subsequent days and persist until the next weak cool front
arrives. While there is at least a slight chance of rain on every
day, at least over the higher terrain of southeast Kentucky, the
best rain chances will come ahead of and along the frontal
boundaries. In sensible terms, look for showers and thunderstorms to
diminish from northwest to southeast Wednesday evening and night
such that only a stray shower or storm is possible by Thursday.
Similar to earlier in the week, temperatures will cool off to the
mid 80s for highs on Thursday and will likely be followed by a
sharper ridge-valley split on Thursday night as high pressure
returns with clear skies and light winds. Look for lows in the upper
50s in northern sheltered valleys to the upper 60s on thermal
belt ridges/slopes. Daily high temperatures rebound to the lower
90s on Friday and lower to middle 90s on Saturday. A stray shower
or storm (10-20% chance) cannot be ruled again on Friday afternoon
and evening, mainly in those counties adjacent to the Virginia
border. Unlike the recent heat that was accompanied by moderate
humidity levels, dew points by Saturday are forecast to rise into
the 70s, which will support oppressive heat indices in the 100 to
105 range for most lower elevation locations. Better rain chances
(30-40%) are also forecast for Saturday afternoon, though again
the higher elevations closer to the Virginia border will be most
favored. The next cold front will brings the best rain chances
(50-70%) of the period on Sunday. Any leftover rain chances become
confined to southeast Kentucky on Monday as cooler and drier air
filters back across eastern Kentucky, holding highs in the mid 80s
for most. Nighttime lows, which rise in the upper 60s to mid 70s
over the weekend, retreat to the upper 50s to mid 60s early next
week behind that front.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
ISSUED AT 125 PM EDT TUE JUN 25 2024

VFR conditions are prevailing across the area and will persist
through much of the TAF period. Increasing and lowering CIGS are
expected over the next few hours as an MCS approaches the area.
However, the MCS is expected to continue to weaken as it
approaches the area with minimal chances for showers and storms.
Lingering cloud cover and the approach of a cold front will lower
CIGS even more across the area but remaining VFR. Opted to add
VCTS to all TAF sites after 12Z/Wednesday with VCTS being possible
at KSYM after 08Z and persisting through the period as the cold
front moves through the region. Lastly, south to southwesterly
winds at less than 10 knots are expected.

&&

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

$$

SHORT TERM...VORST
LONG TERM...GEERTSON
AVIATION...VORST