JKL issues Area Forecast Discussion (AFD) at Aug 27, 4:00 AM EDT263
FXUS63 KJKL 270800
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
400 AM EDT Tue Aug 27 2024
.KEY MESSAGES...
- Hot weather is forecast for several days, with near record
temperatures today through Friday.
- A modest cool-down is expected for the weekend.
- Our greatest potential for rain is Friday into the weekend.
&&
.SHORT TERM...(Today through Wednesday)
Issued at 400 AM EDT TUE AUG 27 2024
As of 03Z surface analysis, surface high pressure continues to exist
over much of the eastern CONUS. Locally, mostly clear skies are over
the area. This has allowed temperatures in the eastern valleys to
fall into the low 60s. Also, the GOES Night Fog satellite channel
has begun to show areas of fog developing in the Kentucky,
Cumberland and Big Sandy River basins. Over the next few hours, fog
will continue to develop leading to reduced visibilities in these
valleys. Fog will burn off a little bit after sunrise and a return
to mostly sunny skies is expected.
Upper-level flow continues to remain well north of the area as a 595
dm dome of high pressure is situated over much of the eastern CONUS.
This ridge will keep the area dry today with high temperatures
climbing into the low to mid-90s. Moisture streamlines around the
center of the high is keeping dewpoints on the lower side as Tds are
expected to be in the 60s. The lower Tds will keep higher heat
indices at bay for today. Also, occurring today, an upper-level
shortwave will track through the Central Plains. At the surface, a
low pressure center will track through the Central Plains into the
Midwest, dragging a weak frontal boundary closer to the area. This
boundary will remain west of the area for today. Overnight tonight,
the front will continue to track eastward but mostly clear skies
will allow for river valley fog to develop again which will burn off
early Wednesday morning.
Wednesday brings another day of mostly dry weather and high
temperatures in the low to mid-90s. However, moisture streamlines
have now shifted to be more south-southeasterly which will advect
moisture into the area. This will cause heat indices to climb closer
to 100 degrees for Wednesday afternoon. Also, the surface low will
be tracking through the Ohio Valley with the cold front dropping
into the Commonwealth. This will trigger isolated showers and
thunderstorms for the end of the period leading into the long-term
period.
Overall, the period will be highlighted by highs in the low to mid-
90s with increasing heat indices to near heat advisory criteria.
Also, an approaching surface low, moving through the Ohio Valley,
will bring increased chances of showers and storms for the end of
the period.
.LONG TERM...(Wednesday through Monday)
Issued at 405 PM EDT MON AUG 26 2024
While the highlight of this long term forecast package is the
potential for record-breaking heat, the passage of a couple of upper
level disturbances will reintroduce rain chances to the forecast in
the second half of this week. On Wednesday, ridging remains parked
over Eastern Kentucky both aloft and at the surface, albeit slightly
further south and east than in days prior. Further north, a
shortwave trough and its associated surface low/frontal boundaries
will move from the Great Lakes into the Ohio River Valley and become
fairly diffuse. Upstream development of Mesoscale Convective Systems
associated with these features appears possible. Any activity that
is able to sustain itself for extended periods of time may traverse
into northern portions of the forecast area on Wednesday, but become
displaced from the best forcing and shear mechanisms as it does so.
The Storm Prediction Center has introduced a marginal (level 1/5)
severe weather risk along and north of the Mountain Parkway on
Wednesday to account for this slight chance of storms, but
uncertainty regarding the evolution of these mesoscale features
limits confidence this far out. Stay tuned to future forecast
updates as these features are resolved in higher-resolution forecast
guidance and near-term mesoscale analyses.
Confidence is much higher in the potential for warmer-than normal
temperatures in the second half of the workweek. The continued
presence of high pressure should produce mostly clear skies and
foster strong diurnal mixing/a potent diurnal temperature curve.
This yields afternoon highs in the mid to upper 90s and overnight
lows around 65 (valleys) to near 70 (ridges) degree range through
Friday. Record highs at KJKL are pretty paltry during this period
of time (93 on Wednesday, 94 on Thursday, and 95 on Friday), so
this heat has the potential to be record-breaking. The
aforementioned, yet subtle, southeastward shift of the parent
synoptic features will gradually facilitate moisture return
through the column as time goes on. Heat indices accordingly climb
above the 100 degree mark on Wednesday afternoon across much of
the area, maximize around 103 on Thursday afternoon, and remain
elevated around 100 on Friday. While this is technically just
below heat advisory criteria, heat-related impacts are certainly
possible, especially in communities with enhanced levels of
exposure and vulnerability to heat hazards. Be sure to stay
hydrated and take breaks if spending time outside this week.
It is worth mentioning that if we see any MCS activity or associated
convective cloud debris in our forecast area on Wednesday or
Thursday, temperatures could under-perform the current forecasts. In
a similar manner, it is plausible that forecast guidance is slightly
overdoing MaxTs. Lower-percentile NBM guidance has been closer to
observed temperatures both upstream and in our area as of late.
Probabilistic DESI guidance still depicts the potential for MaxTs
greater than 97 degrees in a crescent-shaped corridor along and
north/west of the Mountain Parkway and I-75 corridors, but
forecast highs greater than this value appear unlikely. After
coordinating with neighboring offices, the forecast MaxT grids in
the coming days were adjusted slightly downwards from base NBM
output. Ridge-valley temperature splits were added during the
overnight hours as well.
Heading into Labor Day Weekend, another cold front will approach the
area on Friday and pass through on Saturday, this time with better
upper level support and more moisture to work with. Chance PoPs re-
enter the forecast on Friday and then upgrade to likely categorical
PoPs on Saturday with better frontal forcing available. Organized
severe thunderstorm potential still looks low with this second
system, but there should still be enough instability to support
general thunderstorms. The boundary responsible for these storm
chances will stall out over the area this weekend, keeping shower
and storm chances in the forecast through Monday. This lingering
activity should peak each afternoon in accordance with diurnal
heating, although temperatures will be much closer to climatological
norms (highs in the 80s and lows in the 60s) in the post-FROPA
airmass.
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 122 AM EDT TUE AUG 27 2024
VFR conditions are prevailing across all TAF sites and are
forecast to remain largely VFR through the period. MVFR to IFR
valley fog will develop tonight and could impact terminals KSME
and KLOZ before burning off after 12Z/Tuesday. Also, a widespread
4,000 to 5,000 ft cumulus deck is forecast to develop early
Tuesday afternoon and linger into the late evening before
dissipating. Light and variable winds are expected through the
period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...VORST
LONG TERM...MARCUS
AVIATION...VORST
Source:
JKL issues Area Forecast Discussion (AFD) at Aug 27, 4:00 AM EDT---------------
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