JKL issues Area Forecast Discussion (AFD) at Dec 17, 12:07 PM EST
813
FXUS63 KJKL 171707
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1207 PM EST Tue Dec 17 2024
.KEY MESSAGES...
- Thunderstorms will be possible from early Wednesday morning
through early Wednesday afternoon.
- Light snow accumulations will be possible Friday afternoon into
Friday night, mainly for areas along and north of the Mountain
Parkway, and extending southwest along and near Black and Pine
Mountains.
- Below normal temperatures are forecast for this weekend, but
moderating back toward normal temperatures Monday.
&&
.UPDATE...
Issued at 1207 PM EST TUE DEC 17 2024
There is a rather sharp clearing line in south central and
southeast KY, with only some high thin clouds present once the low
clouds depart. Have updated the sky forecast to reflect the latest
obs and progression of clearing. Have also made adjustments for
the timing of precip late tonight and Wednesday based on latest
model runs. It still looks like just about all areas will have
rain at some point in time.
&&
.SHORT TERM...(Today through Wednesday)
Issued at 420 AM EST TUE DEC 17 2024
As of the 06Z surface analysis, a weak surface low is continuing to
work across Canada. Extending southward from the low, an occluding
front exists with a decaying cold front working through the JKL CWA.
This is promoting continued weak shower activity across the area
tonight but those showers are getting close to exiting the
Commonwealth. Behind the exiting cold front, surface high pressure
exists across much of the Midwest and is slowly working southeast
into the CWA bringing dry weather and clearing skies.
Today will feature dry weather and mostly clear skies as surface
high pressure continues to nudge southeast into the forecast area.
With surface high pressure being present, high temperatures will run
above average with highs climbing into the mid to upper-50s.
However, through the day today, a surface low will develop on the
decaying cold front from the overnight. This surface low will then
begin to track northeast toward the JKL CWA with increasing clouds
but the area will remain dry today.
Into the overnight and Wednesday, the decayed cold front will
transition into a warm front that'll lift into the area. Increasing
showers are expected as the front lifts into the Commonwealth. Also,
a couple hundred Joules of SBCAPE are forecast to exist ahead of the
cold front leading to isolated to scattered thunderstorms through
early Wednesday afternoon but mainly for areas along and west of a
line from Prestonsburg to Harlan. Thunderstorms will give way to
rain showers that'll persist through the remainder of the forecast
period. Temperatures will continue to run above average for Tuesday
night into Wednesday morning as overnight lows will range from the
lower-40s across the Bluegrass to lower-50s along the KY/TN border.
Highs for Wednesday, ahead of the cold front will also be above
average as mid-40s will are forecast for the Bluegrass areas and
warming into the lower-60s for areas southeast of the I-64 corridor.
Lastly through the end of the forecast period, total QPF through
FROPA Wednesday night will range from 0.70 to 1.50" across the CWA.
The heaviest QPF is expected be through the heart of the CWA which,
in this instance, is areas northwest of the southeastern high
terrain and southeast of the I-64 corridor.
.LONG TERM...(Wednesday night through Monday)
Issued at 311 AM EST TUE DEC 17 2024
The period begins Wednesday evening with a cold front aloft and mid-
level trough axis departing to the east. Dry air and weak cold
advection over the forecast area will negate any potential impacts
of a weak disturbance moving east across the Bluegrass State to the
south of transitory shortwave upper ridging over the Lower Great
Lakes region Wednesday night into early Thursday. Lows Wednesday
night and highs Thursday will be very close to normal for mid-
December.
Attention then turns to a fast-moving trough with attendant jet
stream that dives southeast from the north-central U.S. Thursday
through the Southeast U.S. Friday. Low-level partial thicknesses
will lower through the early morning hours into the afternoon and
evening Friday, enough so for the thermodynamic environment to be
fully supportive of snow as the p-type, even though surface-level
temperatures will be in the 30s. Models have struggled a bit with
the track, timing and amplitude, but it seems reasonable that with a
surface low and cold front moving across the area followed by low-
level cold advection, there should be at least a chance, if not
likelihood, of light snow with this system Friday into Friday night.
The transitory nature of the system and fast movement of the parent
trough suggest minimal snow accumulations, however, and the WSSI-P
(Probabilistic Winter Storm Severity Index) has trended higher with
low-end Minor Impacts just to the northeast in southern West
Virginia, but as of current forecast package still does not depict
any probabilities for anything other than minimal impacts for
eastern Kentucky. Nevertheless, with high temperatures Friday
trending lower with each run, this is something that may change and
it would not be surprising if the WSSI-P begins to depict low
probabilities for Minor impacts due to snow for parts of
southeastern Kentucky Friday into Friday night, mainly along and
north of the Mountain Parkway. Another shortwave diving southeast in
cyclonic upper flow aloft may allow for flurries or light snow
showers to continue through much of Saturday and Saturday night,
especially along and upwind of the higher terrain.
Surface high pressure over the weekend through Sunday night will
bring cold conditions to the region, especially for daytime highs,
where 30s will be a struggle to reach. The jet stream then retreats
quickly to the northeast by Monday and beyond, allowing for
increasingly warmer air with weak warm advection developing over the
region.
&&
.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
ISSUED AT 639 AM EST TUE DEC 17 2024
All terminals minus KSYM continue to remain in categorical IFR but
over the next few hours, terminals will begin to improve toward
VFR and will remain VFR through much of the afternoon. Overnight
tonight, sites will begin to see a reduction in category as CIGS
will begin to increase and lower into MVFR as a system approaches
from the southwest. With this system, increasing chances of
showers is expected with all terminals beginning to experience
showers by around 09Z/Wednesday. Winds throughout the period will
be light and variable.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...HAL
SHORT TERM...VORST
LONG TERM...CMC
AVIATION...VORST
Source: JKL issues Area Forecast Discussion (AFD) at Dec 17, 12:07 PM EST (https://mesonet.agron.iastate.edu/p.php?pid=202412171707-KJKL-FXUS63-AFDJKL)
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