JKL issues Area Forecast Discussion (AFD) at Oct 1, 9:50 PM EDT315
FXUS63 KJKL 020150
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
950 PM EDT Tue Oct 1 2024
.KEY MESSAGES...
- Showers will affect the area at times until a cold front passes
through eastern Kentucky tonight.
- Behind tonight's cold front, dry weather will arrive on
Wednesday and persist at least through Thursday night.
&&
.UPDATE...
Issued at 950 PM EDT TUE OCT 1 2024
Very little changes made to the forecast grids with this updated.
Just loaded in the latest surface obs and adjusted based on the
trends. Also, updated text and radio products to reflect the
changes. Grids have been saved and sent.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 502 PM EDT TUE OCT 1 2024
The upper low which resided over KY for multiple days has departed
well to the east. However, there's been no change in surface air
mass. With only minimal surface heating today, showers continued
to pop up, but without the upper low, they were more sparse.
As heating is lost this evening, they will begin to die out.
However, a cold front (supported by an upper trough crossing east
over the Great Lakes) is approaching from the northwest and will
move through tonight. This will keep a slight chance of showers
for our area tonight, and in our far eastern counties into
Wednesday morning.
Ridging at all levels will move into our area during the day
Wednesday and persist through Wednesday night. This will finally
bring definitive clearing of the skies for the entire area.
There is at least some degree of fog expected on both nights.
Confidence in how it plays out is not very high for tonight.
Plenty of moisture will be present as we cool down. However, a
cold front will be passing and will bring cold air advection and
bit tighter pressure gradient. This would fight against fog. The
scenario for Wednesday night is more clear cut as a more typical
night for radiation fog.
.LONG TERM...(Thursday through Tuesday)
Issued at 548 PM EDT Tue Oct 1 2024
During the long term forecast period, a couple of cold fronts will
work their way into Eastern Kentucky. Before and after their
passage, broad ridging will keep dry air in place, which will limit
the ability of these fronts to produce widespread convection.
Forecast guidance generally agrees in the placement and the timing
of these longwave features, so confidence in the synoptic set up for
our sensible weather forecast is quite high. However, mesoscale
trends in the ingredients for instability and fog formation will
need to be monitored as these cold fronts approach.
The period opens with a fairly flat 500mb ridge and its associated
surface high pressure in place over the area on Thursday and early
on Friday. Modeled height rises support the idea that high
temperatures will creep up towards the lower 80s by Friday
afternoon, although the broad and flattened nature of this ridge
means that the weak magnitude and the quasi-zonal orientation of
flow throughout the column will not yield in any meaningful moisture
or warm air advection ahead of Friday evening's cold front passage.
The parent upper level trough for Friday's system is not
particularly amplified, and the best dynamic support will remain
north of the Ohio River as a result. The highest rain chances,
albeit only around 25%, will actually be in far southeastern
portions of the forecast area. There, northwesterly flow may combine
with just enough daytime heating to trigger a few showers. This
activity is expected to die down by the overnight hours as the front
clears.
This cycle of ridging-troughing continues this weekend, with ridging
building back in on Saturday and into the daytime hours on Sunday
and troughing swinging down deeper into the Ohio River Valley than
it did on Friday. Skies should be mostly clear for any daytime
activities this weekend, with temperatures progressively warming up
to near 80 degrees once again by Sunday afternoon. While Sunday
night's cold front will be more dynamically supported aloft than
Friday's, its misalignment with the diurnal heating cycle and
antecedent dry air will relegate its ability to produce any
widespread convection. PoPs on Sunday night into Monday morning have
been capped near 35% at this time, with the greatest chances being
across northeastern counties, closer to the upper level support.
Given how far out this is, we will continue to monitor trends in
forecast guidance and make changes accordingly. For now, the most
impactful sensible weather that will come from this system appear to
be the much cooler temperatures that advect in behind it. High
temperatures may struggle to cross the 70 degree mark early next
week, as northerly surface flow and northwesterly flow aloft will
work to advect some of the driest and coolest air so far this fall
into the area. Low temperatures across the entire area will dip into
the 40s.
Aside from the uncertainty regarding instability, questions linger
regarding valley fog potential in the long term forecast. Typically,
ridging yields in the formation of this radiational fog, but the
nocturnal timing of these cold fronts may disturb this. On the other
hand, wet grounds from the associated showers may work to bolster
fog formation outside of the conventional valley spots. As higher
resolution guidance comes in and the time gets closer, these
details will become more clear. For now, patchy valley fog remains
in the grids on most nights in the long term given the favorable
synoptic set up.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
ISSUED AT 738 PM EDT TUE OCT 1 2024
Terminals are currently VFR and will remain VFR over the next
couple hours; however, an approaching cold front will bring
increased rain showers and lowered CIGS. CIGS are forecast to be
MVFR and guidance suggests that with fog development, TAF could
fall into IFR after 06Z/Wednesday. Terminals will remain IFR/MVFR
through the morning with very little improvement through the day.
TAFs will eventually improve to VFR but towards the end of the TAF
period. Lastly, winds will remain light and variable through the
period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...VORST
SHORT TERM...HAL
LONG TERM...MARCUS
AVIATION...VORST
Source:
JKL issues Area Forecast Discussion (AFD) at Oct 1, 9:50 PM EDT---------------
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