JKL issues Area Forecast Discussion (AFD) at Nov 18, 11:20 PM EST307
FXUS63 KJKL 190420 AAA
AFDJKL
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1120 PM EST Mon Nov 18 2024
.KEY MESSAGES...
- Precipitation is expected at times over the next week, mainly
tomorrow through Friday night.
- Above normal temperatures will persist into Wednesday, with any
precipitation occurring as rain.
- Colder temperatures arrive Wednesday night, and much of the area
will likely see precipitation mix with or change over to snow at
times Thursday through Friday.
- At this time, higher elevations of southeast Kentucky have the
potential of realizing some light snow accumulations.
&&
.UPDATE...
Issued at 1120 PM EST MON NOV 18 2024
No significant changes to the forecast with just the inclusion of
the latest obs and trends for the T/Td/Sky grids and a touch up to
the arriving showers late per the latest CAMs. These minor
adjustments have been sent to the NDFD and web servers along with
a freshening of the zones and SAFs.
UPDATE Issued at 755 PM EST MON NOV 18 2024
00Z sfc analysis shows a tightening pressure gradient over
Kentucky between an approaching area of low pressure to the west
and retreating high pressure in the east. This pattern is keeping
the winds stirred from the southeast for much of eastern Kentucky
this evening, but a few of the sheltered spots have been able to
decouple and cool quicker. High clouds, temporarily thinning, will
allow these spots to fall into the lower 50s while the rest of
the area holds in the low and mid 60s. Look for these places to
mix out towards midnight, likely rising a couple of degrees as
more clouds move in, and lower, while the mainly light southerly
winds continue. Dewpoints are also up ahead of the approaching
system and its cold front with most places in the low to mid 50s.
Per the latest CAMs cycles the next round of showers and possible
thunderstorm are on track to be on the doorstep of the JKL CWA by
dawn Tuesday. Have updated the forecast mainly to just add in the
current obs and trends for the T/Td/Sky grids - capturing the
latest terrain distinctions and cloud cover tendencies well into
the night. These minor adjustments have been sent to the NDFD and
web servers.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 438 PM EST MON NOV 18 2024
Pattern aloft will increasingly support unsettled weather across
eastern Kentucky. Shortwave trough lifting northeast out of the
Plains will track through the Upper Midwest & Great Lakes on its
way into southern Canada by the end of the short term. This
feature drags an associated frontal boundary into the Ohio Valley
by tomorrow morning before the frontal zone slows with loss of
better upper level support. The surface front just manages to
enter our forecast area at the end of the short term before
slowing to a crawl. It will take a secondary system to finally
push this surface front completely through eastern Kentucky,
occurring beyond the end of the short term window.
Sensible weather features weather with above normal temperatures
well into the 60s tomorrow. Our eastern valleys and typically
cooler locations across the east will drop into the mid 40s this
evening, but an increasing southerly gradient wind and clouds will
bring temperatures back up across most of the area through the
predawn time frame late tonight. The surface front crosses west to
east through eastern Kentucky Tuesday night. The threat of rain
increases across the area late tonight, with categorical 80-90%
PoPs forecasted over the entire area tomorrow. PoPs taper back
down Tuesday night from evening highs. Maintained the inherited
low chance of thunder (20% or less) late tonight and Tuesday for
consistency. Instability, while elevated, will be marginal at
best. Ensemble probability of CAPE GTE 100 J/kg barely registers.
Overall, QPF has trended lower, but on average around a quarter
to a third of an inch appears possible for most of the forecast
area between late tonight and late Tuesday night.
.LONG TERM...(Wednesday through Monday)
Issued at 554 PM EST MON NOV 18 2024
The models are in generally good agreement with the long wave
pattern through the period. The middle of the week starts out quite
amplified, before the flow becomes more zonal in nature by the
second half of the weekend and early next week. A deep closed low
will be centered over the Upper Midwest on Wednesday, with
troughing fanned south southeast through the middle Mississippi
Valley. This large system will gyre its way east southeast with
time, reaching the Upper Ohio Valley by late Thursday, resulting
in significant height falls across the region. The low will then
wobble more northeast thereafter, hovering over New England by
Friday. 500 mb heights then recover across the Commonwealth into
Saturday and especially Sunday, as the low exits well off to the
northeast and deamplification takes place in its wake.
A progressive cold front will move through eastern Kentucky on
Wednesday, with renewed cyclogenesis taking place over the eastern
Great Lakes, as stout vorticity streams northeast into the region
aloft. Highs will range from the mid 50s near the Bluegrass, to
the mid 60s in far eastern Kentucky, with a non-typical diurnal
temperature range occurring, as the cold front barrels through the
area. Rain chances continue to be more modest during the day,
with 30-50% and only light QPF of less than a tenth of an inch.
Will continue to favor higher winds over the blended guidance,
given the progged stronger wind field within the column. Wind
gusts will likely peak in the 30 to 35 mph range generally along
and west of I-75, and near our Bluegrass counties. A relative lull
in the precipitation continues to look on target heading into
Wednesday night, before the more significant height falls and
vorticity allow for deeper moisture within a cooling boundary
layer.
Some snow will likely be seen at most locations on Thursday. Warm
ground temperatures will prevent accumulation in the valleys.
Elevations above 2000 feet will likely see some accumulation in
the grass, with perhaps Black Mountain experiencing some minor
slush during peak rates, but there is still some uncertainty
regarding these details with it still being in the 60-72 hour
timeframe. Westerly winds will continue to howl, with gusts
perhaps exceeding 35 mph a times in the typically breezier places
during the day. As we head into Thursday night, light grassy and
elevated surface accumulations will be possible that see the more
sustained activity, with minor impacts possible for the highest
elevation roads. Higher rain/snow chances will continue into
Friday, before tapering off from west to east by Friday night and
Saturday, as troughing gradually eases up across the area. Dry
weather will move back in for the second half of the weekend, with
the next chance of rain returning by early Monday, as another
frontal boundary approaches Kentucky.
Temperatures will average well below normal Thursday through
Saturday, with highs in the 40s and lows in the 30s. Did opt for
more of a diurnally limited range for the temperatures compared to
the blended guidance, given the more extensive cloud cover in
place. Temperatures will then moderate back to slightly above
normal by early next week, as return flow ensues out ahead of the
next system.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
ISSUED AT 715 PM EST MON NOV 18 2024
VFR conditions will prevail through the first part of the period,
with some MVFR CIGs developing by afternoon, Tuesday, with even
some IFR level cloud decks setting in for the late afternoon.
Winds will be variable to south-southeasterly at around 5 kts to
start the night before becoming more south-southwesterly into
Tuesday morning. Gradient winds will also increase to between 5
and 10 kts Tuesday, with occasional gusts to around 20 kts,
especially west. Look for a potential of LLWS from the south at
up to 40 kts later tonight - primarily in the western Cumberland
Valley.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GREIF
SHORT TERM...RAY
LONG TERM...JKL
AVIATION...RAY/GREIF
Source:
JKL issues Area Forecast Discussion (AFD) at Nov 18, 11:20 PM EST---------------
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