JKL issues Area Forecast Discussion (AFD) at Jul 26, 5:46 AM EDT196
FXUS63 KJKL 260946
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
546 AM EDT Fri Jul 26 2024
.KEY MESSAGES...
- Mainly dry weather is expected through Saturday.
- There is an increasing threat for excessive rainfall from
multiple rounds of showers and thunderstorms Sunday through
Tuesday, which may lead to the potential for flooding concerns.
- High temperatures will average near normal (mid 80s) through the
middle of next week.
&&
.SHORT TERM...(Today through Saturday)
Issued at 546 AM EDT FRI JUL 26 2024
A slow moving cold front was located near the TN border predawn
this morning, with drier air making its way into eastern KY from
the northeast on the north side of the front. The front is
expected to stall over Middle and East Tennessee today as its
supporting upper level trough over the Ohio valley and New England
begins to depart to the east. This will limit the further
advancement of drier air. Forecast soundings show enough lingering
moisture to result in instability building over the far southwest
portion of the forecast area closest to the front today. Won't
rule out a few showers or thunderstorms popping up there, but dry
mid level air and a lack of significant upper level support will
probably limit development/coverage there, and only a slight
chance POP was used. Any activity should die out with loss of
heating this evening. Saturday looks very similar, with just a
slight chance of a few showers/thunderstorms near the TN border.
For temperatures, afternoon highs are looking fairly seasonal
both days-- mainly in the mid-upper 80s. Tonight's lows will offer
a bit of a respite from summertime mugginess, especially in our
northern counties, where enough dry air should arrive to allow
the cooler valleys to dip into the 50s.
.LONG TERM...(Saturday night through Thursday)
Issued at 538 AM EDT FRI JUL 26 2024
Progressive pattern aloft with the core westerlies remaining
generally along and/or north of the Northern Tier. Extended starts
out with ridging over the Great Lakes and Midwest regions with a
trough over the Atlantic Coast and low over the Central Plains.
This ridging gets pinched off to the northeast as the Plains low
lifts northeast into the Great Lakes and phases with a then
retrograding Atlantic trough/low. This phased feature then moves
northeast into eastern Canada, leaving some part of a weak mean
trough in its wake over the Midwest/Northeast. Pattern become more
murky by the end of the period as additional energy drops into
the Upper Midwest and Great Lakes. At the surface, a weak, but
lingering frontal zone lifts quickly out of the area towards the
Upper Ohio Valley, leaving eastern Kentucky within a warm, moist
air mass. Developing surface low across the Upper Midwest lifts
northeast into Canada, dragging a back across the Midwest by the
end of the period.
Initially, PWATs across eastern Kentucky (north of the frontal
zone) will quite low, Generally less than one inch. But return
flow lifts the boundary northeast out of our area quickly by late
Sunday, allowing PWATS to increase rapidly across the region. A
moisture- laden southwesterly flow ahead of the upstream troughing
will lift PWATs to between 1.8-2.3 inches (at or over the 90th
percentile relative to climatology) by late Sunday/Sunday night.
H850 LLJ does increase across the Tennessee Valley Sunday night,
with a respectable 20-25 kts nosing into eastern Kentucky. This
will provide support for the potential of our first round of
moderate to locally heavy rainfall Sunday night into Monday.
Freezing levels generally below 14 kft combined with storm motions
between 15-20 kts, if correct, are not the most ideal for heavy
rain processes. However, CAPE profiles are more favorable Sunday
night into early Monday, but less so thereafter. We should note as
well that other processes could increase the threat for heavy
rainfall as well, with short term training and convective
backbuilding a possibility as winds profiles become increasingly
unidirectional with time as we progress into Monday proper. The
risk for heavy rainfall could continue into Tuesday with the
phasing of synoptic features aloft over the Ohio Valley and the
approach of a surface cold front into the Midwest.
In anticipation of the risk, WPC has hoisted a Slight Risk for
excessive rainfall across southern portions of the forecast area
Monday and most of southeast Kentucky on Tuesday. At this point,
feel the greatest threat for heavy rain will fall in a window from
Sunday night into Monday. A second round of precipitation on
Tuesday associated more with the trough in place across the Ohio
Valley and the approach of the surface system may keep the threat
of excessive rainfall going, especially after considering that
portions of the area have been hit decently this past week and
conditional on the anticipated QPF from late Sunday though
Monday.
&&
.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
ISSUED AT 546 AM EDT FRI JUL 26 2024
Mainly high clouds were streaming through the skies at the start
of the period. Through holes and thin spots in the clouds, fog
could be seen developing in many valleys. The same general
scenario will persist through sunrise, with the fog continuing to
expand. The fog will likely affect KSME, KLOZ, and KSJS with IFR
conditions at times. The fog will dissipate Friday morning,
leaving mainly VFR conditions until late Friday night. A possible
exception could be in a few thunderstorms around KEKQ and KSME
this afternoon, which may briefly result in sub-VFR condition.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HAL
LONG TERM...RAY
AVIATION...HAL
Source:
JKL issues Area Forecast Discussion (AFD) at Jul 26, 5:46 AM EDT---------------
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