JKL issues Area Forecast Discussion (AFD) at Nov 18, 3:57 AM EST009
FXUS63 KJKL 180857
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
357 AM EST Mon Nov 18 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.
&&
.UPDATE...
Issued at 140 AM EST MON NOV 18 2024
Temperatures have been slower to fall off along and west of the
Pottsville Escarpment where low clouds have been more prevalent.
Thus raised overnight lows slightly over the Bluegrass and Lake
Cumberland areas. Conversely, clearer skies have allowed for the
sheltered valleys of southeast Kentucky to drop off more than
anticipated, warranting a slight lowering in the forecast lows.
Expect lows to range from the upper 30s in the sheltered valleys
to the lower 50s on thermal belt ridges. Overnight forecast is
otherwise on track.
UPDATE Issued at 1050 PM EST SUN NOV 17 2024
The forecast is on track, so have only updated forecast grids
using the latest observations for initialization.
UPDATE Issued at 722 PM EST SUN NOV 17 2024
Made some minor changes to the grids, with the most significant
being to Sky grids with low clouds approaching the area from the
west. Used primarily a blend of CONShort and HREF, which seem to
be a much better solution than the current NBM solution. Will
continue to monitor observed trends and adjust accordingly
through the remainder of the evening.
&&
.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 night through Sunday)
Issued at 357 AM EST MON NOV 18 2024
The forecast period begins with the area on the backside of an
exiting cold front but as the parent low, responsible for the cold
front, is wrapped up into another circulation; the cold front will
be abandoned to the east of the area. The new circulation quickly
develops at the same time as the surface cold front crosses through
the area. This vertically stacked system will quickly eject out of
the Desert Southwest and rapidly move toward the western Great
Lakes. This is the circulation that will absorb that low that
brought the cold front through prior to the start of the forecast
window. As this secondary, stronger system begins to dive southeast
toward the forecast area, increasing cold air will filter into the
region and with the approach of the new system, renewed PoP chances
are expected Wednesday night into Thursday morning as the cold front
dives toward the CWA. With the cold air building into the region and
existing PoP chances, snowflakes may begin to mix into the rain
showers from early Thursday morning through early Friday afternoon.
Thermal profiles through the day support this possibility and a
little more clarity exists with this system as multiple models runs
continue to remain in agreement with this scenario. However, there's
been a slight but little adjustment to the southeasterly location of
the secondary system over the last few runs which could bring in
colder air leading to more snow showers than rain-snow mix. There
are GFS and ECMWF individual ensemble members that portray this
scenario but the went the with NBM solution that starts warmer that
leads to falling temperatures Wednesday night which will lead to
increased rain-snow chances for the remainder of the work week.
Also, must mention that due to widespread above freezing ground
temperatures; snow accumulations aren't expected across the lower
elevation. However, the high terrain across the southeastern
portions of the CWA will be below freezing for the duration of the
event and could lead to light accumulations in those areas.
Lingering backside rain-snow showers will persist through the
morning Friday before warming back up and transitioning to all rain
but as the system pulls off to the northeast, showers will dissipate
from southwest to northeast before coming to an end by Saturday
morning.
Surface high pressure will build back into the area starting
Saturday morning and persisting through the remainder of the
weekend. While surface high pressure exists, upper-level
northwesterly flow will continue to promote CAA into the region and
bring more seasonal temperatures to the area for the weekend.
However, models begin to hint at a possible system developing off
the Rockies early Sunday morning and tracking toward the CWA by
Sunday afternoon. This system is forecast to bring a warm front
through the region and advect warmer temperatures and a return of
rain chances for Monday.
&&
.AVIATION...(For the 06Z TAFS through 06Z Monday night)
ISSUED AT 1250 AM EST MON NOV 18 2024
VFR conditions are forecast to prevail at the TAF sites through
the period. Localized valley fog may occur in southeast KY
early this morning, but shouldn't affect TAF terminals. High
clouds will continue streaming across our area through 06Z
Tuesday. Additionally, a patchy and lower secondary cloud layer
around 5kft AGL will linger through at least late morning/midday
before diminishing/dissipating. Winds will be variable to
southeasterly at around 5 kts today.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GEERTSON
SHORT TERM...HAL
LONG TERM...VORST
AVIATION...GEERTSON
Source:
JKL issues Area Forecast Discussion (AFD) at Nov 18, 3:57 AM EST---------------
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