JKL issues Area Forecast Discussion (AFD) at Nov 5, 7:00 AM EST034
FXUS63 KJKL 051200 AAA
AFDJKL
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
700 AM EST Tue Nov 5 2024
.KEY MESSAGES...
- Above normal temperatures are expected this week, with record or
near-record high temperatures expected today.
- The next chance for widespread measurable rainfall arrives tonight
into Wednesday and lingers into Thursday.
&&
.UPDATE...
Issued at 700 AM EST TUE NOV 5 2024
Forecast is on track early this morning. Interestingly, temps in
our more sheltered and typically cooler locations did eventually
oscillate down into the mid and upper 40s last night. Otherwise,
patchy clouds have been exiting and/or dissipating out of the area
through the early morning hours. Made some adjustments to hourly
temps and winds to bring them in line with current surface obs. No
update to the zones at this time. Updated grids have been issued.
&&
.SHORT TERM...(Today through Wednesday)
Issued at 437 AM EST TUE NOV 5 2024
Forecast begins under a high amplitude pattern aloft, with a
deep, mean western CONUS trough and persistent ridging over the
southeastern CONUS, leaving the Ohio Valley under a southwest flow
regime during the short term. Shortwave trough passing through
the Great Plains and into the Upper Midwest dampens considerably
as it lifts northeast today. What remains of this feature then
proceeds at breakneck speed across the Great Lakes and through
eastern Canada by the end of the period. At the surface, eastern
Kentucky lies between strong Atlantic high pressure and a surface
low passing through the upper Midwest today. A surface cold front
moves from the Missouri Valley eastward into the lower Ohio Valley
by tonight, with its eastern progression slowing and the frontal
zone becoming increasingly oriented in a southwest to northeast
direction right along the Ohio River Valley by the end of the
short term.
Sensible weather features a warm start to the short term...near
record warmth across eastern Kentucky today under the influence of
mostly sunny skies and a robust southerly gradient flow produced by
a tightened pressure gradient between a surface low to our west and
high pressure over the Atlantic to our east. As the aforementioned
surface cold front pushes eastward, reaching the lower Ohio Valley
by tonight, we will see a gradual increase in cloud cover and the
threat of precipitation through the remainder of the short term. The
exact distribution of shower activity will be conditional...actually
heavily dependent on exactly where the frontal zone sets up (stalls)
across the Commonwealth. Model solutions have not been in very good
agreement with the details of this aspect of the forecast.
With respect to thunderstorms, overall instability has not been, nor
is it very impressive. The NBM probability of thunderstorms has
increased with time, from all appearances as a result of the
addition of CAM solutions. For example, the hrrr peaks out at
around 1000 J/kg MUCAPE, and around 750 J/kg MLCAPE by Wednesday
afternoon. However, the NBM probabilities of SBCAPE GTE 500 J/kg
peaks out at only around 30% across our southwestern zones. Other
ensemble suites such as the HREF and LREF are lower. Bottom line,
while the threat of thunder can not be totally ruled out, the
overall probability appears quite low. Be that as it may, will
continue to carry a mention of thunder for collaboration
purposes, collaboration, and because SPC continues to carry our
southwestern portions of our forecast area in a general risk of
thunder.
.LONG TERM...(Wednesday night through Monday)
Issued at 422 AM EST TUE NOV 5 2024
The period is expected to begin with an upper level ridge centered
southwest of Bermuda, with Rafael near or just NW of western Cuba,
an upper level trough axis extending from Ontario southwest to the
Dakotas to the Four Corners region where an upper level low is
expected to be in place, and another ridge over portions of the
eastern Pacific. An upper level low is expected to be centered over
far northern Canada. At the sfc, a ridge of high pressure is
expected to be centered over the Upper MS Valley, and a wavy frontal
zone from the Maritimes to the mid Atlantic states to the Lower OH
Valley to southeastern TX. Downstream of the Four Corner region, an
area of low pressure is expected to be starting to take shape to the
Lee of the Rockies in parts of the central to southern Plains.
Wednesday night through Thursday night, upper level ridging is
expected to remain in place off the southeast U.S. coast/Bahamas to
south of Bermuda while Rafael should work deeper into the eastern
Gulf of Mexico. The northern portion of upper level trough/shortwave
should work east from Ontario to Quebec and across the Maritimes to
Northeast U.S. Another shortwave should trek in the northern stream
from northwest Canada to the Hudson Bay/Manitoba/Ontario area to
Quebec to the eastern Great Lakes while the upper low initially in
the Four Corners should meander to the southern NM. At the surface,
the wavy frontal zone/cold front should gradually sag southeast of
the Commonwealth and to the deep south as Rafael continues to track
west north west and low pressure begins to organize/develop further
south over western TX. Behind the boundary, sfc high pressure is
expected to build from the Dakotas and upper MS Valley and into
portions of the OH Valley, Commonwealth and Appalachians.
Friday through Saturday night, as an upper level trough nears
western Canada and the west coast of the Conus, the upper level low
should move from southern NM to central Plains and toward the upper
MS Valley in advance of the upper level trough working across BC and
into Alberta to the Northern Rockies. At the surface, a sfc low
associated with the upper low tracking across parts of the Plains to
upper MS Valley should track from TX to the upper MS Valley by late
Saturday night while the trailing frontal zone should near the mid
MS Valley to LA/northwest Gulf of Mexico. Meanwhile, the boundary
initially stalled over the deep south should lift north to the Lower
OH Valley, TN Valley and near the southern Appalachians. Further
south, Rafael should meander over northern sections of the Gulf of
Mexico and may begin to begin to merge with the low pressure
system/frontal zone.
Sunday to Monday, the upper level low is progged to work across
portions of the Great Lakes and into Ontario and gradually begin to
merge with the shortwave trough approaching from the west. The
associated occluded low pressure system should track northeast to
the James Bay vicinity while the trailing cold front should work
into the Northeast Conus, mid Atlantic states and then sage across
the Commonwealth and into the Southeast/Southern Appalachians. The
interaction of Rafael/remnants of Rafael with the frontal zone
working into the mid Atlantic states remains uncertain as does the
timing/track of the upper level system over Canada, timing of the
associated cold front into eastern KY and the track of Rafael/
remnants by the end of the weekend. However, guidance continues to
suggest that at least some moisture from the remnants of Rafael
should interact with the frontal zone across eastern KY though there
is considerable spread in timing.
Good chances for showers and perhaps a thunderstorm in a limited
instability regime should linger to begin the long term period Wed
night and Thu near the sagging cold front. High pressure nosing into
the OH Valley and eastern KY behind the boundary should result in a
lull in chances for showers from Thu night through the day on
Friday. With uncertainty in timing, forecast pops return Fri night
and Sat to account for some of the faster guidance, though if recent
operational ECMWF runs were to verify Friday night and Saturday
night would be dry. The end of the weekend to early next week would
feature shower chances per recent operational ECMWF runs as the
frontal zone interacts with tropical moisture/moisture from the
remnants of Rafael while operational GFS runs would be wetter to
begin the weekend and drier early next week to end the period. The
current forecast pops in alignment with NBM are more heavily
weighted toward the slower guidance/recent ECMWF runs.
Temperatures should remain above normal during the long term period
even with the passage of two cold fronts. Departures should be
largest for Thu to Sun by upwards of 10 degrees and 5 to 10 degrees
to begin next week.
&&
.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
ISSUED AT 700 AM EST TUE NOV 5 2024
VFR conditions expected through the forecast period. Regional
satellite is showing skies clearing rapidly across the area.
Southerly gradient winds around 5 kts will increase to around 10
kts with gusts to around 20 kts, veering slightly more out of the
south-southwest. Winds diminish again tonight, with the LLWS
potential increasing late in the period due to the development of
an H850 LLJ of 40 to 50 kts.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...RAY
SHORT TERM...RAY
LONG TERM...JP
AVIATION...RAY
Source:
JKL issues Area Forecast Discussion (AFD) at Nov 5, 7:00 AM EST---------------
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