JKL issues Area Forecast Discussion (AFD) at Dec 7, 6:37 PM EST049
FXUS63 KJKL 072337
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
637 PM EST Sat Dec 7 2024
.KEY MESSAGES...
- Temperatures then warm to above normal readings for Sunday into
early next week, along with the arrival of wetter conditions.
- Periods of rainfall expected to lead to a widespread 0.75 to
1.50 inches of rainfall from Sunday night through Wednesday
morning.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 436 PM EST SAT DEC 7 2024
After a chilly start to the day, southwesterly winds and bright sun
filtered by just a few wispy cirrus have sent temperatures soaring
to near seasonal norms in the 40s (at lower elevations). However,
the air mass remains dry with dew points ranging in the teens.
The delightful weather is due to an ~1027 mb surface high centered
along the Gulf Coast, just east of a 500H shortwave ridge over
the Lower Mississippi Valley. A 500H shortwave trough is also diving
southeast from Northwestern Ontario toward the Northeast CONUS.
Further upstream, an ~570 dam low is centered over the Boot Heel
of New Mexico under a 500H ridge extending from the Northern
Rockies into Western Canada. Upstream from that, a trough is
moving ashore into the Pacific Northwest.
Low-level westerly flow and WAA will become moderately strong
overnight as the the 500H trough passes to our north. Meanwhile, the
surface high will shift east tonight and Sunday while low
pressure takes shape in the lee of the Canadian Rockies.
At the same time, a subtle low pressure wave will take shape
along the Texas Gulf Coast, east of the upper low over the Desert
Southwest. The Pacific Northwest 500H trough crosses the Rockies
to over the Northern/Central Plains while the southwestern closed
low lifts northeast and opens into the the aforementioned trough.
These two low pressure system will generally shift toward the
Ohio Valley through the short-term while high pressure departs
into the Atlantic. The first low occludes and passes to near Lake
Superior while the second low lifts into the Ark-La-Tex. The low-
level flow weakens aloft on Sunday before ramping up again Sunday
evening/night as we come under the influence of the southern
stream lows's warm conveyor belt jet. As PWATS surge to over 1
inch (in excess of the 90th percentile relative to climo), clouds
will thicken and yield to widespread rainfall Sunday night. LREF
probs for at least 0.5 inch of rain through 12z Monday range from
30 percent in Pike County up to 90 percent near Lake Cumberland.
In more sensible terms, expect mostly clear/clear skies to favor
rapid decoupling of the boundary layer this evening. Temperatures
are forecast to drop rapidly in the sheltered valley locales, at
least initially. However a tightening pressure gradient and
strengthening low-level flow could lead to some mixing later in
the night, particularly on ridges and in the flatter
Bluegrass/Lake Cumberland area. Confidence in sporadic mixing
reaching into the sheltered valleys is lower confidence but
cannot be ruled out. Forecast low temperatures range from the mid
20s in sheltered valleys to the mid 30s on thermal belts and in
exposed terrain along and west of the Pottsville Escarpment. Lows
are likely to be established early in the night before
temperatures hold steady or rise later in the night. Confidence in
forecast low temperatures in sheltered valleys east of the
Escarpment is lower as realized values will depend on the amount
of mixing which occurs -- more mixing leading to warmer low
temperatures and and vice versa. A much warmer day is store for
Sunday with highs in the 50s to near 60 in spite of increasing
clouds. Widespread rain is expected to quickly overspread the area
from the southwest Sunday evening with temperatures falling back
into the 40s.
.LONG TERM...(Monday through Saturday)
Issued at 334 PM EST SAT DEC 7 2024
Monday, rain will likely be ongoing in the morning. Highs Monday
are expected to rise into the upper 50s to low 60s. Winds will be
out of the southwest 10-15 mph with gusts up to 15-20 mph during
the afternoon. Light showers will continue through the afternoon,
but may be limited, and lighter in intensity due to decreased
moisture behind an upper level shortwave. Monday's lows will be
in the mid to upper 40s as cloud cover will remain, likely keeping
temperatures from dropping colder.
Into Tuesday, moisture starts to return to the area, as a
positively tilted trough begins to draw moisture up from the Gulf
Of Mexico ahead of the incoming vort max and subsequent cold
front. This will likely lead to rain Tuesday increasing in
coverage and intensity through the afternoon. Highs are expected
to rise into the upper 50s. Some locations could hit 60. Heading
into the evening, winds will begin veering from southwest to
northwest. This will dry the column out some. Lows will drop into
the upper 20s to low 30s, leading to rain changing over to a
wintry mix and eventually snow showers by Wednesday morning.
Wednesday, the trough axis pivots east of the area. At this time
snow showers look to taper off heading into the afternoon. Little
to no impacts from any wintry precip are currently expected.
Highs Wednesday will be cooler in the mid to upper 30s. Ridging
moves in from the east behind the exiting trough, leading to skies
clearing out heading into Thursday. With clearing skies Wednesday
night, expect temperatures to cool off a bit more. Currently,
forecasted lows are in the low 20s for much of the area.
Thursday and Friday, quiet weather returns, with high pressure
briefly building into the area. This will help bring warmer air in
to the state through Saturday. Highs Thursday are expected to be
in the mid to upper 30s, upper 40s on Friday, and low 50s
Saturday. There's model discrepancy on timing of the next weather
system, however next precipitation chances look to return either
Saturday or Sunday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 637 PM EST SAT DEC 7 2024
VFR TAFs are expected for the entire TAF period; however,
increasing and lowering CIGS are expected for the last few hours
of the TAF as a disturbance approaches from the southwest. Ahead
of the the approaching disturbance, LLWS will develop overnight
and persist through the early morning before surface winds
increase and negate LLWS and move more toward turbulent mixing.
Sustained southwesterly winds around 10 knots with gusts to 15 to
20 knots are expected after 14Z/Sunday for all terminals.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...GEERTSON
LONG TERM...GINNICK
AVIATION...VORST
Source:
JKL issues Area Forecast Discussion (AFD) at Dec 7, 6:37 PM EST---------------
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