JKL issues Area Forecast Discussion (AFD) at Nov 16, 7:04 PM EST357
FXUS63 KJKL 170004
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
704 PM EST Sat Nov 16 2024
.KEY MESSAGES...
- Temperatures rise to around 10 degrees above normal Sunday
through the first half of next week.
- Rain chances return late Monday night into Tuesday and continue
through the rest of the work week.
- A colder pattern by mid to late next week brings the potential
for gusty winds and wintry precipitation.
&&
.UPDATE...
Issued at 704 PM EST SAT NOV 16 2024
Lowered temperatures this evening in line with observed trends,
and also made somewhat significant changes to the Sky grids to
also reflect latest observed trends. Other changes were minimal.
Used the latest observations as the initialization to the gridded
forecast.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 327 PM EST SAT NOV 16 2024
The afternoon surface analysis shows that high pressure has crested
across the Upper Ohio Valley and near the Great Lakes region. There
is good agreement on this area of high pressure pushing east, with
the mid-level ridging shifting east too. We have seen good erosion
of the pesky stratus deck and now much of the Lake Cumberland and
Cumberland Valley regions are under mostly sunny to sunny skies this
afternoon. This will continue to erode from southwest to northeast
through the remainder of the afternoon and into the evening. Given
some will see a more diurnally limited day we could see this
translate to some more prevalent fog and or stratus through the
night. The latest forecast soundings including HREF mean forecast
soundings show this potential, but still some concern as to how this
shakes out. Given this did expand the fog some, but still opted to
kept it more confined to the river valleys. Overnight lows could
also be tricky given the fog potential and even some higher clouds.
Therefore did raise them a bit to better match this trend. However,
this will have to be watched through the evening to see how these
trend through the evening into tonight.
The high pressure is expected to push east and southerly flow will
kick in at the surface. This return flow will make it quite a bit
warmer with afternoon highs in the mid to upper 60s for most
locations. The will be under mostly sunny skies. Monday night, will
be another tricky one with lower clouds showing up once again in the
forecast sounding data. Therefore, wondering how much of split we
will see in the overnight lows and right now they might be a little
on the strong side with low to mid 40s in the valleys and upper 40s
to around 50 on the ridges. However, it also could be a night where
we drop off in the evening before maybe rising some overnight. This
will have to be monitored, as even some high clouds will work in
from the upper level trough digging into the Southern Plains.
.LONG TERM...(Monday through Saturday)
Issued at 524 PM EST Sat Nov 16 2024
The long term forecast period is defined by a rather active weather
pattern. On Monday, a northern stream disturbance will slide through
Ontario while a deepening upper level trough quickly ejects out of
the southern Rockies and moves into the Central Plains. At the
surface, this first system will be marked by a stalled boundary
north of the Ohio River. As the weather pattern becomes more
progressive, the aforementioned boundary will lift north as a warm
front. Behind it, warm and moist air advection should allow for
plentiful cloud coverage, and perhaps some sprinkles, on Monday.
Temperatures will remain above climatological averages, with
highs ranging from the mid 60s across our cloudier northern
counties to near 70 degrees across the south. Monday night's MinTs
look to be similarly mild, averaging about 50 degrees.
For the rest of the week, the attention shifts towards the evolution
of the second storm system. By Tuesday morning, the initial surface
cyclone associated with this feature will be positioned somewhere in
the Upper Midwest. Its trailing cold front will push through the
Ohio River Valley during the daytime hours on Tuesday, bringing
substantial rain chances to the entirety of the forecast area (70-
75% PoPs). A few rumbles of thunder cannot be ruled out, especially
across the antecedently warmer southern counties, but widespread
organized convection is not expected at this time. While
temperatures on Tuesday are expected to be slightly cooler than they
were on Monday, this will likely be due to the effects of
evaporative cooling and relatively enhances cloud coverage. The
strongest post-FROPA cold air advection is expected to lag this
surface front, as it will race ahead of its mid/upper level
support as it moves into our forecast area. Expect above-average
highs in the mid to upper 60s and overnight lows in the vicinity
of 50-55 degrees on Tuesday.
On Wednesday, the upper level support from Tuesday's system will
begin to phase with a vigorous, negatively-tilted trough propagating
into the Plains from the Pacific Northwest. Most forecast guidance
agrees that these two troughing features will consolidate into a
robust and very large closed upper level low by Wednesday afternoon.
This will position the Ohio River Valley in a regime of divergent
upper level atmospheric flow and favorable cyclonic vorticity
advection. Rain chances look to increase once again on Wednesday
afternoon and Wednesday evening as a new surface cyclone develops
and then drifts north-northeast.
As the pressure gradient tightens during cyclogenesis, surface winds
will accordingly increase in magnitude. Sustained winds up to 20mph
appear plausible, with widespread gusts up to 30 mph expected,
especially at higher elevations. Once this cyclone moves north of
the Ohio River, surface winds will shift to a more westerly
orientation and the flow aloft will become northwesterly. This
yields in quite effective cold air advection on the backside of the
cyclone. Overnight lows on Wednesday will flirt with the freezing
mark, and high temperatures on Thursday will struggle to rise above
40 degrees. Low temperatures on Thursday night into Friday morning
will once again approach the freezing mark, and these blustery
conditions are expected to persist through Friday as the cyclone
spins over the region. With sufficiently cold temperatures in place
both at the surface and aloft and strong low level lapse rates
likely, wintery precipitation enters the forecast grids once the
aforementioned cold air advection kicks in on Wednesday night. At
first, a mixture of rain and snow appears most likely, but a
stronger signal for freezing temperatures on Thursday and Friday
nights could yield in a few areas of snow showers. The greatest
chances for accumulating snow will be in the coldest mountain areas
along the Virginia border, but the increased wind speeds are likely
to relegate the effectiveness of this accumulation. Other portions
of the forecast area may see a few flakes fall, but the above-
freezing daytime temperatures through the end of the forecast period
will keep widespread accumulation chances low. The system is
expected to depart the area by Saturday, and precipitation chances
will taper off from southwest to northeast as it does so. Regardless
of precipitation type, the sensible weather in Eastern Kentucky late
next week looks to be rather blustery and rather dreary.
It is important to note that while a signal for wintery
precipitation and gusty winds does exist in much of the available
forecast guidance for next week, significant run-to-run differences
in the various deterministic models have been observed. Small
details in the positioning of the parent cyclone will affect the
exact amounts of wraparound moisture entering the area and the
related atmospheric thermal profile, which in turn affect the
likelihood of winter precipitation. Thus, at this temporal range, a
single deterministic model's output can and will change drastically
from run to run. Interested parties are encouraged to stay tuned to
ensemble trends and future forecast issuances as they relate to this
system.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 610 PM EST SAT NOV 16 2024
All locations have improved to VFR conditions under clear skies,
with the exception of KSJS where clearing is about to occur just
in time to begin the TAF period. High clouds will begin to move
across the region later tonight through the remainder of the TAF
period, though models might be overdoing this given fairly sparse
coverage upstream. We could see mostly river valley fog tonight
given the diurnally limited day for most. That said, this is not
expected to affect the TAF sites at this time. Winds will remain
light and variable at TAF sites.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...CMC
SHORT TERM...DJ
LONG TERM...MARCUS
AVIATION...CMC
Source:
JKL issues Area Forecast Discussion (AFD) at Nov 16, 7:04 PM EST---------------
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