JKL issues Area Forecast Discussion (AFD) at Dec 10, 6:52 PM EST
691
FXUS63 KJKL 102352
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
652 PM EST Tue Dec 10 2024
.KEY MESSAGES...
- Rain redevelops tonight and transitions to a brief period of
snow on Wednesday morning before ending.
- Minor snow accumulations are expected Wednesday morning, most
notably at elevations above 2,000 feet.
- Snow showers, a few briefly heavy, could bring additional minor
snow accumulation Wednesday evening into Wednesday night.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 529 PM EST TUE DEC 10 2024
Regional radar mosaic shows a line of showers extending from
Inez to Hazard to Middlesboro at 22z. A MSLP/observations
analysis reveals that this line of convection is along a cold
front that is slowly sliding eastward through Coalfields. Ahead of
the boundary, temperatures range in the mid to upper 60s at lower
elevations while temperatures have dropped into the 50s behind
the boundary. A notable wind shift from southwest to northwest is
also noted with the boundary. This cold front extends southward
from an ~1008 mb low centered over far southeastern Ohio all the
way to the Mississippi River Delta. The front precedes a longwave
trough extending from the Central Canadian Arctic to northeast
Mexico. A potent vorticity lobe is found just east of the trough
axis from Illinois down the Central Texas. Further poleward within
the trough, an ~506 dam low is diving southward through Manitoba.
A secondary surface cold front is found ahead of this upper low
from near International Falls, MN to to over Nebraska and then
northwestward along the eastern slopes of the Northern Rockies.
The cold front presently crossing the area will shift off to the
east over the next couple of hours before becoming nearly
stationary. The associated showers will follows suit until
reaching the immediate vicinity of the Virginia border where they
are likely to train southwest to northeast through the evening.
Rainfall rates should be low enough to preclude any hydro issues.
Additional energy riding up the eastern side of the trough will
initiate a new surface low riding along the stalled front after
midnight, causing the precipitation shield to expand
northwestward over the Coalfields again through the wee hours of
Wednesday morning. Meanwhile, ongoing low-level CAA will push
temperatures downward through the night and into the mid 30s to
mid 40s, west-to-east, by around 5 AM EDT. Meanwhile, high
resolution models are showing a northeast-to-southwest oriented
band of snow developing over Indiana/Western Kentucky after
midnight due to zone of enhanced lifting/frontogenesis ahead of
the aforementioned vorticity lobe. That band is depicted as
generally broadening and intensifying as it moves eastward across
the Commonwealth and gains access to better moisture, eventually
merging with the precipitation shield over eastern Kentucky. As
the surface low passes to our east of the Appalachian Mountain
spine early Wednesday morning, cold air will rush in from the
west, drop temperatures into the lower to mid 30s, and flip rain
over to all snow between 5 AM and 9 AM EST. A brief period of
sleet is possible as the transition occurs, primarily east of the
Pottsville Escarpment. The snow continues light to moderate at
times before tapering off in the Lake Cumberland area as early as
7 AM EST, lingering as late as 12 PM EST over Pike County. The
warm antecedent ground and air temperatures should limit
accumulations to less than one half inch primarily on grassy and
elevated surfaces across a majority of the area. The area with the
best chances for impactful accumulation is from Martin down to
Bell County and eastward where the snow will persist the longest
and snowfall rates will be highest. In this area, up to around one
half inch of snow accumulation is forecast in valleys and up to 2
inches is possible at elevations above 2,000 feet (the higher
amounts may be enough for some instances of sloppy snow sticking
to highways). Once the snow ends, clouds are expected to break
partially and allow temperatures to warm back into the mid to
upper 30s at lower elevations during the afternoon.
As temperatures warm at the surface, cold air advection in the low-
levels ahead of the secondary cold front will lead to steepening
lapse rates Wednesday evening. Model soundings suggest that these
showers will have excellent access to the dendritic growth zone
which combined with moderately strong background flow could lead
to squall-like conditions in the heaviest activity. The equilibrium
level could flirt with -20C, perhaps even supporting enough
charge generation for a rumble of thunder in the most robust
updrafts. The snow showers wane to just a few flurries during the
late evening and early overnight as cold, dry air rushes in
behind the secondary front. Due to the showery nature of the
snowfall, accumulations could vary over short distances. The snow
showers could briefly coat pavement at some lower elevation
locales, but warm surface temperatures should tend to melt off
most of the snow that tries to accumulate. Grassy and elevated
surfaces should fare better, picking up to one half inch of new
accumulation in most cases. An isolated amount nearing an inch
cannot be ruled out. Temperatures are expected to fall into the
upper teens to mid 20s, northeast to southeast, by late Wednesday
night.
.LONG TERM...(Thursday through Tuesday)
Issued at 555 PM EST TUE DEC 10 2024
The 500H trough axis departs to our east Thursday morning with
subsequent ridging building eastward through Thursday night. An
associated surface high crests over eastern Kentucky Thursday
evening. Chilly 850 mb temperatures down to around -5 to -10C
yield to moderating temperatures on the backside of the surface
high on Thursday night and Friday. Thereafter, a rather active
pattern ensues with the first of two Pacific 500H troughs passing
over the Ohio Valley this weekend, supporting an area of low
pressure passing to our north. The system's associated cold front
drops south of the Ohio River and stalls overhead or nearby
Sunday night. This boundary does little to cool our air
temperatures. The second storm system of Pacific origin then
approaches toward the end of period, though model agreement is not
great with respect to the details at this time.
In sensible terms, expect partly cloudy to most clear skies Thursday
and Thursday night. Temperatures will be chilly with highs only in
the mid 30s north to around 40 near the Tennessee border while lows
dip back into the mid 10s to mid 20s Thursday night. Clouds
increase on Friday while winds pick up from the southeast,
boosting temperatures into the mid 40s to lower 50s. Temperatures
dip back into the 20s and 30s Friday night, holding steady or
rising late. Rain chances return Saturday and peak Saturday night
(80-90 PoP) before tapering off on Sunday. After a lull in the
rain chances Sunday night and Monday, the threat for rain
increases again Monday night into Tuesday. Forecast day high
temperatures from Saturday through Tuesday range in the 50s while
night temperatures bottom out in the mid 30s to mid 40s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
ISSUED AT 652 PM EST TUE DEC 10 2024
Lowering cigs with deteriorating flight rules will continue to
move west to east across the forecast area over the next few hours
behind a slow-moving cold front. An uptick in precipitation
follows well after midnight as temperatures drop to near freezing,
transitioning the precipitation over to snow around and after
sunrise on Wednesday. Conditions improve late morning through the
afternoon before scattered snow showers develop and move into the
area from the west, mostly after 21z. Though extremely low
confidence, a few lightning strikes are possible with the snow
showers at the end of the TAF period Wednesday.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...GEERTSON
LONG TERM...GEERTSON
AVIATION...CMC
Source: JKL issues Area Forecast Discussion (AFD) at Dec 10, 6:52 PM EST (https://mesonet.agron.iastate.edu/p.php?pid=202412102352-KJKL-FXUS63-AFDJKL)
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