JKL issues Area Forecast Discussion (AFD) at Dec 15, 4:48 PM EST
905
FXUS63 KJKL 152148
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
448 PM EST Sun Dec 15 2024
.KEY MESSAGES...
- Above normal temperatures persist through Wednesday.
- Periods of rain are forecast to impact the area at times through
Wednesday night.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 347 PM EST SUN DEC 15 2024
Damp conditions linger as showers slowly diminish from west to east
late this afternoon. Temperatures are seasonably mild, ranging
from the upper 40s in portions of the Licking and Big Sandy River
basin up to the mid 50s in the vicinity of Lake Cumberland. The
surface analysis shows a warm front draped from the Southern
Appalachians northwestward roughly along US-421 across eastern
Kentucky and further northwest to a dissipating occluded low over
southern Wisconsin. The system's cold front extends southward
through the Mid-Mississippi Valley and then turns westward into
the Red River Valley of the South where it becomes a warm front.
Looking aloft, an ~558 dam closed low is moving toward Lake Erie,
leaving the remnant occluded surface low be smothered by a shortwave
ridge building along and west of the Mississippi River. The next
500H trough (of Pacific origin) is crossing the Northern/Central
High Plains.
As the aforementioned cold front moves into the Lower Ohio Valley
this evening, it will stall and become more east-west oriented.
The 500H shortwave ridging passes over our region tonight.
Meanwhile, a new low pressure system will organize along the North
Dakota/Canadian border this evening. This new system's 30+ knot
warm conveyor belt jet will shift east and overspread eastern
Kentucky late tonight. The resulting warm air advection and
isentropic upglide will cause shower coverage to increase again
toward sunrise Monday. The showers will tend to most persistent
toward the Ohio River during the day on Monday where there will be
a lingering baroclinic zone from the former cold front. As the
new surface low tracks into northern Ontario and becomes
increasingly occluded on Tuesday evening, a cold front extending
south from this low, will drop through the Commonwealth and bring
a round of widespread rain showers, sinking from northwest to
southeast.
Sensibly, the showers continue to dry up this evening and exit Pike
County by or before 9 PM EST. Low clouds, patchy fog, and spotty
drizzle and the possibility of a light shower then linger for
most of tonight. Temperatures will be mild by December standards
only settling back into the middle and upper 40s. Showers
redevelop from the west toward sunrise, with likely PoPs reaching
the I-75 corridor around 4 to 5 AM and spreading eastward into
Pike County by 8 to 9 AM EST. After the initial surge in shower
activity, the steadier shower activity is expected to become more
confined to near and north of the Mountain Parkway during the
midday hours. In fact, locations near and south of the Hal
Rogers/KY-80 corridor should be mainly dry for 3 or 4 hours during
the midday to mid afternoon. Shower coverage should then increase
again from the northwest from mid-afternoon onward as the next
cold front approaches from the northwest and crosses the area
during the evening hours. Showers taper from northwest to
southeast Monday night behind the front. Temperatures remain very
mild reaching into the upper 50s to lower 60s on Monday afternoon
before falling back into the 40s for most locales on Monday night.
Rainfall amounts of 0.5 to 1.0 inch are forecast through Tuesday
morning, highest amounts northwest.
.LONG TERM...(Tuesday through Sunday)
Issued at 447 PM EST Sun Dec 15 2024
At the start of the long term forecast on Tuesday morning, the cold
front responsible for Monday's active weather will have lost its
upper level support. While said front and its associated cloud
cover/precipitation chances are likely to clear the entirety of our
forecast area by Tuesday afternoon, it will stall out to our south
somewhere in the Tennessee Valley. In its wake, a surface high
pressure system will build into the area and foster clearing. Quasi-
zonal flow aloft and the return of sunshine will allow for
temperatures to recover into the mid/upper 50s across much of the
area on Tuesday.
However, this reprieve from the rain will not last long, and the
progressive nature of the synoptic pattern aloft means that a trough
will begin to dig into the greater Mississippi River Valley on
Tuesday night into Wednesday. At the surface, this will be
represented as a deepening surface low pressure system, which is
expected to quickly eject northeast out of ArkLaTex and into
Kentucky by Wednesday morning. The stalled boundary will then lift
northeast across the Commonwealth as a warm front, with cloud
coverage and rain chances increasing accordingly. Temperatures may
not follow a traditional diurnal curve overnight into Wednesday
morning, with temperatures beginning to rise area-wide after 06z.
Together, these synoptics will shift flow throughout the column to a
more southwesterly orientation, and the resultant warm air advection
and moisture return looks seasonably potent. While this set up does
not look particularly concerning from an organized severe weather
standpoint, a rumble of thunder cannot be ruled out on Wednesday
afternoon/evening. Afternoon highs could top out near 60 across our
southern counties, and the last few cycles of long-range
probabilistic guidance has been highlighting the potential for some
marginal instability down there. The parent upper level trough will
progress eastward into Thursday, leading to FROPA late Wednesday
night. Cold air advection kicks in behind it, and a very brief
changeover to a rain-snow mix is possible before precipitation
quickly tapers off on Thursday morning.
The rest of Thursday's sensible weather looks dry, but it marks the
beginning of a cooler pattern. Deeper, longwave upper level
troughing emerges over the eastern half of the CONUS by next
weekend, with more amplified ridging out west. High temperatures
will drop down into the 40s on Thursday and Friday, with overnight
lows dipping near/below freezing again. A clipper-type system
embedded in the NW flow around this longwave troughing will approach
the area on Friday, and with the colder airmass in place, some light
snow could materialize, especially across the higher terrain in our
eastern counties. However, there remains some uncertainty in the
exact timing of these features and the amount of moisture available
to them, so confidence in accumulating snow is low. Confidence is
higher that this system will reinforce the cold air headed into the
weekend, with forecast highs in the mid/low 30s on Saturday and
Sunday and overnight lows in the 20s/teens. Some guidance resolves
an embedded upper level shortwave disturbance approaching the area
on Saturday, which could once again lead to precipitation chances in
areas prone to upslope flow. With the colder air in place, it could
fall as snow, but it is far too early to provide any details
regarding impacts. Therefore, interests with pre-holiday travel
concerns should continue to monitor the forecast in the coming
days.
&&
.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 123 PM EST SUN DEC 15 2024
Varying conditions ranging from LIFR to VFR are noted across
eastern Kentucky at TAF issuance due to showers. These showers
will gradually diminish from west to east through 00z, leaving
low ceilings (generally MVFR) and patches of fog, drizzle, and
spotty light showers for most of tonight. The next surge of shower
activity arrives from the southwest around/after 9-11z near SME
and spreads northeast to SJS by 13-15z. Winds will average south
at 10kt or less to end the period. Though lower confidence, there
will be renewed threat of LLWS after 12z.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...GEERTSON
LONG TERM...MARCUS
AVIATION...GEERTSON
Source: JKL issues Area Forecast Discussion (AFD) at Dec 15, 4:48 PM EST (https://mesonet.agron.iastate.edu/p.php?pid=202412152148-KJKL-FXUS63-AFDJKL)
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