JKL issues Area Forecast Discussion (AFD) at Nov 17, 5:04 PM EST184
FXUS63 KJKL 172204
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
504 PM EST Sun Nov 17 2024
.KEY MESSAGES...
- Precipitation is expected at times over the next week, mainly
Tuesday 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
could see precipitation occur as snow at times after that
point, but little or no accumulation is expected.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 452 PM EST SUN NOV 17 2024
Surface high pressure near the southeast coast, along with ridging
aloft, will keep our weather dry through into Monday night.
However, we will be having effects from a system further west. A
strong upper level closed low currently just south of AZ will
track northeast to MN by Tuesday morning, supporting a deep
surface low on a similar track. A broad area of warm air advection
will persist east of the low and around the western and northern
side of the surface high. The isentropic lift will bring varying
amounts of clouds to our area. We are already seeing high, thin
clouds spilling through the upper level ridge. Increasing lower
level moisture has resulted in clouds as far east as central KY
this afternoon. Further advection/lift will probably bring lower
clouds to our area overnight and into Monday, but the extent of
the clouds is still in question.
As the aforementioned storm system tracks northeast across the
upper Midwest, flow off the gulf coinciding with sufficient upper
level support will result in an area of showers progressing east
over KY ahead of the system's cold front. They will most likely be
entering our western counties by dawn.
For temperatures, light winds and warm air advection will be
favorable for another night of ridge/valley differences tonight.
However, should low clouds become prominent enough, it would
temper the differences. Monday will be another mild day, with the
amount of sun factoring into exactly how mild. Strengthening low
level flow (as well as increasing clouds) will keep the
ridge/valley low temperature differences more limited on Monday
night, with the eastern and southeastern valleys the most likely
places to decouple and chill.
.LONG TERM...(Tuesday through Sunday)
Issued at 503 PM EST Sun Nov 17 2024
The long term forecast period continues to be characterized by a
rather active weather pattern with two distinct periods of
precipitation. At the start of the forecast period, an occluded
surface low pressure system will be ejecting out of the Northern
Plains and into Canada. The cold front associated with this system
is expected to outpace this low, and it will be on our doorstep by
Tuesday afternoon. Out ahead of it, showers appear likely, and PoPs
between 80 and 90% are in the forecast grids accordingly.
Temperatures during this first round of precipitation will be the
warmest that they will be for the duration of the long term forecast
period. This means that all precipitation in the first round of
activity will fall as rain, and there may be just enough instability
out ahead of the front to squeeze out a few rumbles of thunder.
Expect afternoon highs in the mid 60s and overnight lows to drop
into the 50s.
The upper level support for this first round of rain is expected to
phase with a potent Pacific trough throughout the day on Tuesday. By
Tuesday evening, these features will have consolidated into a closed
upper level low, which is then anticipated to strengthen and shift
southeast towards the Ohio River Valley/Great Lakes on Wednesday.
Post-FROPA, strengthening westerly surface winds and strengthening
flow aloft associated with this upper low will advect cooler and
notably drier air into the region. Wednesday's forecast guidance
continues to trend drier, and some degree of clearing appears likely
(especially across our southwestern counties) during the late
afternoon and evening hours. Chance PoPs remain in the grids for
now, but it is beginning to look like the area could see a lull in
precipitation on Wednesday evening. Wednesday's afternoon highs will
be a few degrees lower than they were on Tuesday, but the potency of
the cold air advection associated with this system becomes more
noticeable. Aided by relatively clearer skies, temperatures will dip
into the 30s across the entire area on Wednesday night into Thursday
morning and set the stage for some potential winter weather.
As this cooldown materializes, wraparound moisture and lobes of
favorable cyclonic vorticity will wrap around the upper level low
and advect into the forecast area early Thursday morning. These
ingredients will combine to produce a second round of precipitation
chances, which will linger around throughout the end of the work
week. With the colder air in place, brief periods of wintery
precipitation are possible, but there a great deal of model
uncertainty continues to shroud this forecast. Around sunrise on
Thursday, surface temperatures will flirt with the freezing line,
and some guidance continues to resolve favorable thermal profiles
aloft for snow. Snow appears most likely in the higher terrain, such
as up on Black Mountain along the Virginia border. For the rest of
the forecast area, a cold rain mixed with some snowflakes is
currently the mostly likely solution, and the grids reflect this.
With blustery winds out of the northwest, ongoing precipitation, and
plentiful cloud coverage, temperatures on Thursday afternoon will
struggle to warm above 40 degrees. Gusty winds and antecedently warm
ground temperatures will limit snow accumulation. As temperatures
cool off to near freezing again on Thursday night/Friday morning,
another switchover to mixed snow/rain showers is possible, but aside
from the colder mountaintops, most precipitation on Friday afternoon
should fall as rain under a slightly warmer airmass. At this
temporal range, however, it should be noted that future changes to
this forecast are possible. Interested parties should pay close
attention to forecast updates in the coming days accordingly.
By the weekend, the upper low will eject up into the Northeastern
states, and drier air should advect back into the forecast area on
its backside/ahead of a building ridge. Precipitation tapers off on
Saturday from SW to NE as a similar clearing trend emerges. Under
the clearer conditions, Saturday night could be the coldest night in
the period, with lows in the upper 20s possible, especially in
valleys. However, the return of partially sunny skies during the
daytime hours will allow high temperatures to moderate back towards
the low/mid 50s this weekend. This would be a welcome relief from
the rather dreary/windy/chilly conditions forecast with this late
week system and a return to the climatologically-expected conditions
of Eastern Kentucky in late November.
&&
.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 111 PM EST SUN NOV 17 2024
VFR conditions are forecast at least through late tonight.
Localized valley fog may occur in southeast KY overnight, but
shouldn't affect TAF sites. Low clouds are forecast to develop
from northwest to southeast tonight, but there is uncertainty
regarding the extent of clouds and their height. NAM BUFR forecast
soundings suggest ceilings at least as low as MVFR, while the GFS
forecast soundings are less aggressive and generally suggest VFR
conditions. NAM MOS guidance holds off on MVFR conditions until
around dawn (except in our southwest, where it remains VFR). Have
generally followed the NAM MOS, but confidence is not high.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HAL
LONG TERM...MARCUS
AVIATION...HAL
Source:
JKL issues Area Forecast Discussion (AFD) at Nov 17, 5:04 PM EST---------------
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