JKL issues Area Forecast Discussion (AFD) at Nov 12, 12:45 AM EST954
FXUS63 KJKL 120545 AAA
AFDJKL
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1245 AM EST Tue Nov 12 2024
.KEY MESSAGES...
- A cold front will increase chances for rain from Wednesday night
to Thursday evening.
- Temperatures will be be a few degrees below normal Tuesday
through Friday, with the exception of Wednesday.
&&
.UPDATE...
Issued at 1230 AM EST TUE NOV 12 2024
No significant changes to the forecast with just the inclusion of
the latest obs and trends for the T/Td/Sky grids for the update.
These minor adjustments have been sent to the NDFD and web servers
along with a freshening of the zones and SAFs.
UPDATE Issued at 1007 PM EST MON NOV 11 2024
Not many changes made to the grids as they've been largely on
track. Just a few touch-ups based on the latest surface
observations and updates to Sky grids based on latest satellite
imagery. Lastly, updated evening text and radio products based on
the changes. Grids have been saved and sent.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 413 PM EST MON NOV 11 2024
Late this afternoon at the axis of n upper level trough extended
from the Hudson Bay region to the Northeastern Conus to the
Carolinas. A shortwave trough/upper low moving through the upper
level trough was over the lower St Lawrence valley headed to the
Maritimes while another shortwave trough/upper low was working
into the eastern Great Lakes. An upper level ridge was centered
from Mexico into the western Gulf of Mexico with ridging north
through TX to the Dakotas while a trough was working into the
western Conus. At the surface, the front that crosses the region
last night into this morning was working across the Appalachians
with a ridge of high pressure having nosed into the Lower OH
Valley from the Southern Plains. Another sfc low was moving from
Ontario into Quebec with the associated cold front nearing the
Lower OH Valley from the mid MS Valley. A sfc ridge high pressure
was in place from Manitoba and western Ontario into the Dakotas
and upper MS Valley. Drier air has moved into eastern KY behind
the first cold front with current dewpoints generally ranging
through the 40s though afternoon mixed dewpoints in some cases
were in the upper 30s.
Tonight and Tuesday, the shortwave trough nearing the eastern
Great Lakes at present will rotate into the Northeast and then to
the Maritimes to western Atlantic with the axis of the mean upper
level trough also working well east of eastern KY. Meanwhile, the
upper level ridge to the west will work east across the Plains
and build into the MS Valley and then to the western Great Lakes
to the Lower OH Valley to the Gulf of Mexico. To the west, an
upper level trough will work deeper into the western Conus and
then to the Rockies. Tuesday night, the axis of the upper level
ridge will shift to a James Bay to eastern Great Lakes to
Southern Appalachians to eastern Gulf of Mexico line. At the
surface, the upstream cold front will drop to near the OH River
during the early to middle part of the evening and into eastern
KY late in the evening into the overnight hours. This boundary
should sag south of eastern KY by dawn as sfc high pressure
building east across Ontario and into the Great Lakes and into the
Lower to Middle OH Valley and eastern KY. This boundary will
become more diffuse on Tuesday as it sags further south as high
pressure at the surface and aloft dominates with rising heights
expected at 500 mb. High pressure at the surface and aloft will
continue to dominate on Tuesday night as well as both shift east.
Behind the boundary tonight, PW is progged to fall to the 0.2 to
0.3 inch range if not slightly lower, or climatologically below
the 10th percentile for this time of year, with only a modest
increase in PW to about 0.2 to 0.4 by late Tuesday night. 850 mb
temperature, especially in the north and east will be a couple of
degrees colder on average compared to today.
The cold front tonight may bring a bit of an increase in mixiness
as it passes so the timing and intensity of fog formation in
deeper valleys is uncertain. In addition, there will be a bit of
increase in moisture generally below 850 mb as the front passes so
a few to scattered low to mid level clouds cannot be ruled out.
Otherwise, any lingering clouds and valley fog should lift and
mix on Tuesday morning and give way to mostly sunny to sunny
skies. Under high pressure shifting eastward and a trend to
southerly gradient/flow for ridges, a moderate ridge/valley split
is expected for Tuesday night. Some deeper valley fog may again
form, especially south of the Mountain Parkway.
.LONG TERM...(Wednesday through Monday)
Issued at 335 PM EST MON NOV 11 2024
Model suite suggests a high amplitude, progressive pattern aloft
through the extended with the core of the westerlies, or main
corridor of strongest steering winds generally established across
the heart of the CONUS. We start the extended with ridging aloft
over the Ohio Valley, with a trough over the Great Plains. Unlike
previous storm systems of late, this trough has no issues with the
ridge over the east, and moves eastward with east into the Midwest
and Ohio Valley. This trough pushes across our region at a fast
clip, with the axis passing east of our area by the end of the day
Thursday. Ridging builds back over the Ohio Valley and remains there
until a shortwave trough slides southeast across the Great Lakes and
into the Ohio Valley by the end of the forecast window. At the
surface, a cold front passes through eastern Kentucky during the day
Thursday, clearing the area by Thursday evening. This front is quite
potent and forms over the Plains by the start of the period, then in
quick fashion reaches our forecast area in less than 36 hours. High
pressure then transits the Ohio Valley until the end of the period,
when another cold front manages to drop southeastward from the Upper
Midwest and into the Commonwealth. The remainder of the long term
discussion will focus on the mid-week system.
Sensible weather features an uptick in active weather across the
region, mainly due to the polar jet dropping further south. The
remnants of a tropical wave remains over the Gulf of Mexico. As
the surface front races eastward Wednesday into Thursday, a
considerable amount of moisture is drawn northward from the
tropical wave over the Gulf of Mexico. PWATS increase rapidly
across the TN Valley and climb to between 1 and 1.3 inches ahead
of the front by the time it enters our area. A 50kt plus H850 jet
streak nosing its way into the area Wednesday night combined with
good divergent flow aloft should help produce some good lift in
the column above the region. All said this will help set the table
synoptically for favorably high rainfall totals. One limiting
factor will be the speed of the system through our area. Ensemble
probabilistic data supports this scenario as the probability of
GTE 0.5 inches of rainfall across eastern Kentucky is between
55-75%. Probabilities of GTE 0.25 inches is between 80 and 90%. So
this next system could turn out to be a solid wetting rain, and
possibly soaking rain for the entire area. Obviously there are
portions of the area that sorely need the rainfall.
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 1245 AM EST TUE NOV 12 2024
VFR conditions will prevail across all TAF sites through the
aviation forecast period. Fog is likely to develop overnight but
will not filter into any of the TAF sites. Lastly, winds are
forecast to be light and variable with a slight in bump in
northeasterly winds Tuesday afternoon.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GREIF
SHORT TERM...JP
LONG TERM...RAY
AVIATION...VORST/GREIF
Source:
JKL issues Area Forecast Discussion (AFD) at Nov 12, 12:45 AM EST---------------
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