JKL issues Area Forecast Discussion (AFD) at Sep 14, 6:06 PM EDT
168
FXUS63 KJKL 142206
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
606 PM EDT Sat Sep 14 2024
.KEY MESSAGES...
- After high temperatures well into the 80s in most places this
weekend, a slight cool-down arrives for the upcoming weekdays.
- Dry weather lasts through Monday, followed by a small potential
for showers at times Monday night through Friday.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 421 PM EDT SAT SEP 14 2024
The short term will feature a blocking pattern with high pressure in
charge across much of the Ohio Valley, and the remnants of the
tropical system Francine to our south across the TN Valley and Deep
South. This will also combine with an additional tropical system
coming into the southeast Atlantic coast. Kentucky will find itself
wedged between the upper level high and low pressure systems.
Overall it seems as though the upper level ridge and surface high
pressure will prevail through the short term period across eastern
Kentucky.
Diurnally driven CU and a few small pop-up showers in the far SW
will quickly diminish this evening with the loss of daytime
heating/mixing. Predominate winds will also dissipate quickly into
the overnight. Good radiational cooling and subsidence will allow
temps to fall well into the upper 50s and low 60s both tonight and
Sunday night, with coolest temps in the deeper valleys. While each
night the last couple nights has yielded less and less fog as we
continue to trend drier, it's still possible that some of the deeper
valleys could see patchy fog overnight, especially in the far east.
Kept the mention in the forecast for tonight, and again tomorrow
night as well. The daytime hours tomorrow will be very similar to
today, with some diurnal cu likely to develop, though likely a bit
more limited as Francine starts to drift farther away from eastern
KY and we trend drier overall. Due to our position on the south side
of surface high pressure, winds will continue to be predominately
out of the east, generally between 5 and 10 mph with some higher
gusts in the afternoon. Afternoon temperatures will also be very
similar to that of today, with highs in the mid 80s, and only light
humidity.
.LONG TERM...(Monday through Saturday)
Issued at 423 PM EDT SAT SEP 14 2024
After one more day under the influence of the ridging component of
an upper level Rex Block, the attention in the long term forecast
period shifts towards a tropical disturbance located off the coast
of the Carolinas. The National Hurricane Center currently gives this
system a 40-50% chance of developing into a (sub)tropical depression
or storm, and forecast guidance suggests that it will interact with
the remnant circulation of Francine as it drifts towards the coast
on Monday. Models are struggling to resolve the specifics of this
interaction and subsequently disagree on the evolution, phasing, and
intensity of this system. In general, the GFS continues to be the
more aggressive and quicker forecast model, whereas the European
model is slower. The former pushes the system much further inland
and across the Appalachian mountains, whereas the latter keeps its
remnants centered over Virginia. Notably, both models demonstrate
some degree of wraparound Atlantic moisture reaching the Ohio River
Valley during the long term forecast period, although the amount of
moisture and the timing of this advection vary quite a bit. Compared
to yesterday's model suite, there is a bit more consensus that this
system will squeeze out some showers in Eastern Kentucky next week.
Yet, uncertainty still lingers given the climatologically anomalous
pattern, and the exact timing of the greatest rain chances is likely
to change in future forecast packages.
Confidence in Monday's forecast is high, when a surface high pressure
system and upper level ridging should work to keep the area mostly
dry. Mid to high level clouds should begin to stream off this
tropical system and into our area as the day progresses, which will
keep afternoon highs in the low 80s as opposed to this weekend's mid
80s. These cirrus-type clouds might create rather vivid sunrises and
sunsets before mid-level moisture arrives and fosters thicker clouds
by Tuesday.
For the rest of the week, the increased cloud coverage will relegate
MaxTs to near or just below the 80 degree mark and MinTs to the
upper 50s/lower 60s. The potential for ridge-valley splits and
radiational fog will be mitigated by these clouds, but both may
still materialize in southwestern portions of the area. Places such
as London, Monticello, and Somerset will be the furthest removed
from the moisture and forcing associated with the tropical system
and will thus see less cloud coverage and lower rain chances
throughout the long term forecast. On the other hand, eastern and
northern portions of the forecast area that are closer to this
developing system will be more likely to see some rainfall and
enhanced cloud coverage. Given the slightly better model alignment
than yesterday, the NBM has categorically upped PoPs from less than
25% slight chances to about 40% chances in the eastern third of the
forecast area. This seems reasonable, and rain chances will peak
each afternoon in accordance with the diurnal heating cycle. It is
important to note that the positioning of this particular tropical
system will translate to flow with northerly components. As a
result, wide downsloping appears less likely than it did with
Francine, and if the system retrogrades westward, orographic lift
could locally enhance rain chances in northward-facing terrain. This
system will be working against some dry air leftover in the column
from this past weekend's ridging, and forecast rain totals reflect
this. Any rain that falls from this system will likely be more
stratiform in nature than the intense/convective type that one might
associate with tropical cyclones. Significant impacts from this
system across Eastern Kentucky are not expected at this time.
Instead, we will see chances for some beneficial rain, and these
chances might increase further as higher-resolution guidance comes
into perspective. We once again encourage interested parties to stay
tuned to future forecast updates as confidence increases and the
exact details regarding this system's evolution are nailed down.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 606 PM EDT SAT SEP 14 2024
Aside from localized late night/early morning valley fog with IFR
or worse conditions, VFR conditions will prevail. Fog should not
affect TAF sites. Winds will be less than 10 kts from the east or
southeast.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...JMW
LONG TERM...MARCUS
AVIATION...HAL
Source: JKL issues Area Forecast Discussion (AFD) at Sep 14, 6:06 PM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202409142206-KJKL-FXUS63-AFDJKL)
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