JKL issues Area Forecast Discussion (AFD) at Nov 13, 4:04 PM EST585
FXUS63 KJKL 132104
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
404 PM EST Wed Nov 13 2024
.KEY MESSAGES...
- An approaching cold front will bring a shot of wetting rains to
eastern Kentucky from tonight into Thursday evening.
- Temperatures will be near normal through Sat, before trending to
near 10 degrees above normal for the first half of next week.
- Rain chances return Monday night into Tuesday.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 355 PM EST WED NOV 13 2024
Late this afternoon, an upper level ridge was centered in the
vicinity of southern FL with the axis of this ridge extending into
the eastern Great Lakes to Quebec. Meanwhile an upper level trough
extended from west of Hudson Bay to the upper MS Valley to the
Arklatex vicinity with another ridge extending from Mexico north
to the Four Corner to eastern MT and into Canada while another
trough was nearing the west coast of the Conus. At the surface, a
ridge of high pressure extended from eastern Quebec to the mid
Atlantic states to GA and FL while an area of low pressure was
centered in the vicinity of Kansas City. A warm front extended
east from the low into western KY to the Cumberland Plateau of TN
to eastern TN and was nearing the southwest portion of the CWA. A
cold front meanwhile extended from the low into eastern and
southern TX with a ridge of high pressure behind it extending from
portions of the Great Basin to western and central TX. Locally,
clouds have been increasing ahead of the approaching trough and a
lead shortwave that is working into and across the Lower OH
Valley and TN Valley regions. Convection is also occurring west
and southwest of the area with showers associated with this
feature and the warm front lifting north toward central and
eastern KY. The dry airmass lingering from the departing ridging
with PW currently ranging from about 0.25 in eastern Pike County
to near 0.7 inches near Lake Cumberland and southeasterly flow
with a downslope component off of higher terrain northeast TN and
SW VA has allowed some valley locations to climb to around 70
degrees or roughly 10 degrees above normal for mid November.
Tonight and Thursday, the lead shortwave trough will work
northeast and across the area this evening while the main trough
axis/upper level low lingers to the west of eastern tonight. This
upper level low should reach the central IL vicinity near dawn on
Thursday. A plume of rather deep moisture will advect into the
region ahead of this upper level trough and the associated sfc
system. This sfc low should near Chicago around dawn on Thursday
with the warm front having lifted north of the area overnight and
the trailing cold front extending across western KY to middle TN
to the mouth of the MS vicinity at that point. PW is progged per
the 12Z HREF to climb to the 0.6 inch far eastern CWA to 1.4
inches near Lake Cumberland by midnight tonight and then peak in
the 1.1 to 1.3 inch range for the remainder of the area overnight.
Rather robust omega is expected within this moist layer ahead of
the 500 mb trough as some PVA combines with with some jet dynamics.
The deeper moisture will already have begun to shift east of
central KY by dawn on Thursday. The upper level low is progged to
track across the Lower to Middle OH Valley on Thursday with the
axis of this associated trough working east of eastern KY by
Thursday evening. PW is progged to drop to 0.6 yo 0.75 by the
afternoon and evening. However, the colder air working in from the
west will lead to an increase in mid level lapse rates to near or
possibly in excess of 7C/km from west to east late Thursday
morning into the afternoon. This combined with daytime heating per
recent RAP runs should support MLCAPE of around 100 to 300 J/kg
and MUCAPE a bit hither than that. This scenario will support
showers and isolated thunder as the sfc low passes north of the
area into OH while the cold front moves into eastern KY from
midday into the afternoon.
Thursday night, the upper low is expected to track to the southeastern
VA/northeastern NC area with rising 500 mb heights late following
the pass of a shortwave during the evening HREF to first half of
the night. The low level flow will have an upslope component with
lingering low level moisture during Thursday night resulting in
upslope/instability showers.
A wetting rain is expected across the area with most locations
likely to receive a good soaking. By 7 PM EST on Thursday the 12Z
HREF probability of at least 0.5 inches of rain is 70 to near 100
percent across the entire area. The lowest probabilities are
downwind of Black Mountain and Pine Mountain in rain shadowed
areas of northeastern Harlan County over into Letcher and southern
Perry counties. Probabilities to at least an inch by that point
per the 12Z HREF are in the 30 percent to 100 percent rang with
the lowest probabilities in the same rain shadowed areas mentioned
above with the highest probabilities near Lake Cumberland,
northeastern Pike County and areas generally north of the Mtn
Parkway.
.LONG TERM...(Friday through Wednesday)
Issued at 402 PM EST Wed Nov 13 2024
Confidence remains high in the long term forecast period through
this weekend, with the forecast guidance suite in remarkably good
agreement through Sunday night. On Friday, some residual rain
showers remain in the forecast, especially in areas along the US-23
corridor. These eastern counties will be closer to the better upper
level support, but rain chances will gradually decrease as the
parent trough departs. Northwesterly flow throughout the column
behind this feature will advect cooler and drier air into Eastern
Kentucky by Friday evening. As a result, expect cloud coverage to
slowly taper off overnight into Saturday morning. Before then, this
daytime cloud coverage and the aforementioned CAA will work together
to relegate afternoon highs on Friday to the mid 50s, with overnight
lows in the lower half of the 40s. Patchy to areal fog is possible
on Friday night and Saturday morning. Antecedent wet grounds will
aid in fog formation, and the greatest coverage will be in our river
valleys and in our southwestern counties, where the clouds will
clear first.
Most available forecast model guidance resolves an upper level ridge
building back into the Ohio River Valley this weekend, and its
associated surface high pressure system will slide through the area
at the same time. As these features move in, veering surface winds,
rising heights, and subsidence will moderate temperatures and clear
the skies. Saturday will be the sunniest day in the long term
forecast period, and strong diurnal mixing will yield our classic
ridge-valley temperature splits by Saturday night. Expect afternoon
highs near 60 degrees and overnight lows near 40 on the ridgetops.
Valleys, particularly the sheltered and seasonally shaded ones, will
cool into the mid 30s on Saturday night. Valley fog, especially in
the Cumberland basin, appears possible once again, although
increasing cloud coverage to the north and to the west could limit
coverage. Sunday will be cloudier, but warmer than Saturday as
moisture and warm air stream into the atmospheric column. Sunday's
afternoon highs are expected to be in the mid 60s, with lows in the
mid 40s.
Confidence is beginning to increase that Monday's forecast will
remain drier and warmer. Models still resolve a northern stream
upper level disturbance in the greater Ohio River Valley region
early next week, but now collectively position this feature north
of the river itself. As a result, the best ingredients for
precipitation will likely remain displaced from our forecast area
on Monday, although the clouds associated with this feature remain
in the forecast. This is supported by the warm and moist air
advection that models resolve out ahead of a second, southern
stream disturbance in the southern Plains. This second feature
will eject into the Midwest by mid-week in the form of a
negatively-tilted trough. While questions linger regarding the
magnitude of moisture return and the efficacy of warm air
advection out ahead of this system, it will need to be monitored
closely for convective thunderstorm potential given the dynamics
at play aloft.
Thunder has been left out of the forecast grids for
now, but likely PoPs (up to 65%) re-enter the forecast on
Tuesday. Afternoon highs could warm back up into the 70s early
next week, although ensemble member spread is markedly higher for
the end of the forecast than it is for the beginning. Therefore,
interested parties are encouraged to stay tuned to future forecast
updates as the latest model guidance comes in.
&&
.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
ISSUED at 109 PM EST WED NOV 13 2024
VFR will prevail across the region for the first 12 hours of the
period as high pressure exits and an upper level disturbance and
cold front being to approach. Some reductions in ceilings or
visibility to MVFR in showers may occur in the west and northwest
between 03Z and 06Z as mid and then lower clouds and showers
arrive from the west. Thereafter, a deterioration in ceilings to
MVFR should occur from west to east through 12Z within an area of
showers ahead of a cold front with visibilities to MVFR or even
IFR levels at times. MVFR ceilings and spotty IFR ceilings with
some MVFR and IFR reductions in visibility should prevail during
the last 6 hours of the period. Some thunder may occur within
showers overnight and perhaps with some development near the cold
front itself late in the period. Confidence in areal extent and
timing was not high enough to include at this point. Winds will
average from the southeast at 5 to 10 KT through about 06Z, before
trending to the south or event southwest near KSME to end the
period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...JP
LONG TERM...MARCUS
AVIATION...JP
Source:
JKL issues Area Forecast Discussion (AFD) at Nov 13, 4:04 PM EST---------------
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