JKL issues Area Forecast Discussion (AFD) at Nov 20, 6:36 AM EST347
FXUS63 KJKL 201136
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
636 AM EST Wed Nov 20 2024
.KEY MESSAGES...
- Colder temperatures arrive tonight, with snow expected to be
seen in the air in most places at times from Thursday into
Friday.
- Locations most likely to receive impactful snow accumulations
are those elevations above 1500 feet, mainly Thursday night.
&&
.SHORT TERM...(Today through Thursday)
Issued at 435 AM EST WED NOV 20 2024
Current surface analysis over the CONUS continues to be active as a
large surface cyclone is spreading impacts across the eastern half
of the CONUS. The large surface low is currently parked over
southern Manitoba and extending from the low, an occluded boundary
is draped across the eastern Great Lakes. Further south, a weak
cold front is slowly tracking through the Ohio Valley back toward
the Southern Plains. To the east of the triple point, a warm front
is draped across the Mid-Atlantic. Locally, the area is under the
regime of the warm sector with low stratus clouds and areas of dense
fog. Due to the areas of dense fog, a Dense Fog Advisory was issued
to cover the main thoroughfares of I-64 and the Mountain Parkway
through 9 AM this morning. Temperatures across the area continue to
remain rather mild as widespread upper-50s to low-60s exist. Also,
weak showers are slowly working across the CWA but will largely
dissipate by later this morning. Lastly, a Winter Weather Advisory
was issued for Harlan and Letcher counties for the upcoming winter
weather event for the end of the forecast period.
Through the today, that large surface low and its vertically stacked
components will gradually dive southeast into the Great Lakes. While
that occurs, the cold front that's was situated over much of the
Ohio Valley will drift through the region. While the occurs,
increasing showers are forecast from later this morning through this
evening before tapering off and ending by the overnight hours. Along
and ahead of the front, increasing southwesterly winds are expected
as sustained 10 to 15 mph winds with gusts upwards of 25 mph are
likely through frontal passage. Also, due to the increase in
southwesterly flow, temperatures are forecast to climb into the
upper-50s to lower-60s with the high occurring sometime later this
morning before FROPA ushers in CAA causing those temperatures to
fall across the region going into tonight. As CAA advection and
drier air builds into the region overnight, clearing skies will
allow overnight lows to fall into the mid-30s but those falling
temperatures will be limited as cloud cover is forecast to build
in the early morning hours.
The second component of this complex system will build into the area
for Thursday morning and persist through the end of the forecast
period. The pesky surface low that's been plaguing the eastern
CONUS for the last couple of days will continue to dive southeast
into eastern Ohio Valley and bring renewed chances of PoP starting
early Thursday morning and persisting through the remainder of the
forecast period. The CAA that built in overnight Wednesday primes
the area with colder temperatures which will allow a large portion
of the precipitation to fall as snow. Widespread accumulations
aren't expected on Thursday as ground temperatures are above
freezing but snowfall rates may allow for some light accumulations
on elevated objects and grassy surfaces. The best locations for
accumulating snow will be the southeastern high terrain along the
Virginia border. As the high terrain is expected to be below
freezing through much of the event, accumulating snow is expected
and enough to justify the Winter Weather Advisory that was posted
with this morning forecast package. Snow showers will persist
across the area into the long-term forecast period.
.LONG TERM...(Thursday night through Tuesday)
Issued at 540 AM EST WED NOV 20 2024
Confidence is increasing for the first accumulating snowfall across
most of eastern Kentucky Thursday evening into Friday morning. The
20/00z model suite is is good agreement at the beginning of the
period. Around 00z Thursday, a deep ~526 dam low will be rotating
over Western Pennsylvania. At the surface, an ~992 mb triple
point coastal low will be lifting to near New York City while its
weakening parent occluded low is pivoting around the backside of
the upper low and into Northern Indiana.
Snow showers (possibly a few squalls) and resultant wet-bulb
cooling from earlier in the afternoon and evening on Thursday are
expected to suppress air temperatures to near freezing at many
locations as the occluded low drops toward the mid-Ohio Valley
Thursday evening. The hi-res models are in good agreement on a
shield of stratiform snow developing from northwest to southeast
Thursday evening due to warm air advection lifting ahead of the
surface low. Warm ground/pavement temperatures will tend to
hinder accumulation. However, moderately strong synoptic lifting
into the dendritic growth zone, orographic lifting along and
upwind of Pine/Black mountains and temperatures falling below 32F
at elevations above 1,500 feet will likely allow for the snow to
overcome warm pavement temperatures in far southeastern Kentucky.
This has warranted the issuance of a Winter Weather Advisory for
those counties with significant infrastructure at elevations above
1,500 feet. In these counties, anticipate generally 2 to 4 inches
of accumulation between 1,500 and 3,000 feet with locally higher
amounts possible above 3,000 feet. Outside of the higher terrain,
air temperatures remain more marginal, likely limiting
accumulations to between a dusting to an inch for most locations
and then mainly on grassy and elevated surfaces. However, it is
important to note that various model solutions are hinting at a
potential northwest-to-southeast oriented swath of locally heavier
snow. While it is still to early to definitely pinpoint where
this could occur, later shifts will continue to assess this
potential and any possible need for another targeted Winter
Weather Advisory.
As the remnant occluded low departs early Friday morning,
continued low-level warm air advection will cause the snow to mix
with rain again at lower elevations as the steadier precipitation
departs. A lull in the precipitation is likely midday Friday
before another spoke of energy rotates around the upper low late
in the afternoon through early overnight. Model time
heights/soundings cast doubt on maintaining temperatures cold
enough for in-cloud ice, especially after 00z Saturday. Thus any
wintry precipitation over the southeastern mountains may tend more
towards a freezing rain or drizzle Friday night. Any impacts to
highways from this should be negligible. Air temperatures are
forecast to recover to near 40 degrees on Friday at lower
elevations and into the mid 30s above 2,000 feet. Cloud cover and
the warmer air mass should keep low temperatures on Friday in the
mid 30s for most of the lower elevations east of I-75. Partial
late night clearing may allow temperatures to dip to near freezing
west of I-75. That clearing gradually works east on Saturday as
the upper level low and any leftover showers, drizzle or flakes
depart. Saturday's forecast highs are around 10 degrees warmer
than Friday, ranging in the upper 40s to lower 50s.
In the wake of the upper low, surface high pressure builds in at the
surface while the upper level flow trends quasi-zonal. A broad upper
level trough skimming the Northern Plains will foster a low pressure
passing to our north early next week while dragging a cold front to
over the Ohio Valley. This boundary could become a focus for one or
more waves of low pressure in the new work week, though there is
substantial spread in the model solutions. Temperatures recover
quickly this weekend reaching the mid to upper 50s for highs on
Sunday and remaining in the vicinity of 60 degrees through Tuesday.
Nighttime lows moderate similarly from the upper 20s to mid 30s on
Saturday night to the mid 40s to low 50s by Monday night.
&&
.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
ISSUED AT 636 AM EST WED NOV 20 2024
IFR/LIFR conditions are prevailing across all TAF sites and will
continue to be that way as low CIGS and low VSBY are plaguing all
TAF sites. There will be gradual improvement over the next few
hours as a cold front dives into the area. This front will bring
increased PoP chances after 15Z through 00Z; as well as, gusty
westerly winds. Westerly winds sustained around 10 knots and gusts
to 20 knots are expected through frontal passage before shifting
to the northwest post-frontal. Once the front crosses through this
afternoon/evening, CIGS will gradually begin to increase from IFR
to MVFR and then VFR after 00Z and winds will slacken to light
and variable. Winds are forecast to increase again overnight
toward the end of the TAF window as an upper-level low dives
southeast into the region. This will bring another round of
lowered CIGS and increased PoP chances.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 9 AM EST this morning for KYZ044-
050>052-059-060-104-106.
Winter Weather Advisory from 7 PM Thursday to 10 AM EST Friday
for KYZ087-113-115-117-120.
Winter Weather Advisory from 4 PM Thursday to 10 AM EST Friday
for KYZ088-118.
&&
$$
SHORT TERM...VORST
LONG TERM...GEERTSON
AVIATION...VORST
Source:
JKL issues Area Forecast Discussion (AFD) at Nov 20, 6:36 AM EST---------------
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