JKL issues Area Forecast Discussion (AFD) at Jun 19, 3:50 PM EDT956
FXUS63 KJKL 191950
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
350 PM EDT Wed Jun 19 2024
.KEY MESSAGES...
- Hot and mainly dry weather will occur through the weekend.
Afternoon heat indices may peak near 100 at some locations.
- The upper level high/ridge bringing our heat wave will weaken
during the weekend and eventually allow a cold front to at
least approach the area, with the POP peaking at 40-50% Sunday
night ahead of the front.
- Uncertainty now exists concerning the progress of the cold front
next week and whether or not a substantially drier air mass
will arrive. A small POP is maintained into next week due to the
uncertainty.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 350 PM EDT WED JUN 19 2024
The models were in good agreement regarding the large scale flow
pattern aloft in the short term. A strong ridge of high pressure
will be in place across most of the eastern third of the CONUS to
begin the period, and will be the dominant weather feature for
eastern Kentucky. Persistent, fairly widespread high clouds, along
with scattered low clouds, will steadily dissipate this evening and
tonight, and should give way to mostly clear skies overnight. A
couple of models did try to push a weak disturbance aloft through
the region, sparking isolated showers and storms over portions of
the area on Thursday, especially during the afternoon. However,
confidence in this scenario unfolding is quite low at this time, due
to the strength of the ridge that will be in place and the amount of
dry air that is expected to be in place through out the low levels
of the atmosphere. For those reasons, we kept precip chances well
below 15% for tomorrow, but still within tolerance with our
neighbors to the north and west. An increase in cloud cover is now
included on Thursday to account for the potential passage of the
weak disturbance aloft over the surface ridge during the afternoon.
That all being said, it still appears that Thursday will be dry.
As for tonight, with ridging in place nearly overhead, very light
winds, and steadily decreasing cloud cover, the stage will be set
for at least a modest ridge valley temperature split. Fog will also
possible again tonight for the same reasons the temperature
differences are possible. With much less cloud cover in the forecast
for tomorrow than what we saw today, and with ridging still in
place, we should see temperatures warming into the lower 90s around
the area. Heat index values in the low to mid 90s will be possible
as well.
.LONG TERM...(Friday through Wednesday)
Issued at 350 PM EDT WED JUN 19 2024
A broad upper level high centered over the Tennessee and lower Ohio
valleys at the start of the period will be weakening and dropping
further south as we move into the weekend. This process will be
helped along by a couple of shortwave troughs traversing through the
prevailing westerlies aloft to our north. They will lead to a larger
low/trough developing and tracking eastward through the Great Lakes
and northeast CONUS region Saturday into Tuesday. This will send the
southern edge of the faster flow aloft southward over the eastern
CONUS, with initially west and then northwest flow occurring over
our area.
The evolution of the upper level pattern will allow a cold front to
at least approach our area at the start of the new week. A rather
amorphous surface pattern with little air flow over our area at the
beginning of the period will give way to southwesterly winds ahead
of the cold front by Sunday. This should bring a flow of warm, moist
air over the region ahead of the front. Along with gradual cooling
aloft as geopotential heights fall, it could allow for some limited
deep convection Saturday and Sunday. This is shown in the GFS, but
not the ECMWF. However, the low level moisture in the ECMWF seems
too limited (surface dew points only in the upper 50s to near 60),
and have decided to make a mention of a slight chance of precip.
There is growing disagreement in the models regarding the eventual
progress of the cold front. The GFS is becoming less aggressive
and has the front stalling and dying without any meaningful change
in our air mass. This allows periodic convective precip through
Wednesday. Meanwhile, the ECMWF as of its 00Z run still had a
definitive cold fropa on Monday, with a much drier air mass
arriving behind it. Either model supports at least a modest
increase in POP to chance category Sunday night. The question is
what happens after that. Given the trend of the GFS and the
forecast uncertainties, a low POP mention is being included
through Wednesday.
&&
.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
ISSUED AT 120 PM EDT WED JUN 19 2024
VFR conditions are expected to prevail through the end of the TAF
period. BKN high clouds will prevail through the rest of today,
but should steadily decrease in coverage after dark, with mostly
clear skies on tap by late this evening. Winds will average
between southerly and easterly at less than 5 kts through the
period. Some fog is expected to form overnight in valleys across
the area, but chances of fog directly impacting any of the TAF
airports are low enough to not warrant mention of fog in the TAFs
at this time.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...AR
LONG TERM...HAL
AVIATION...AR
Source:
JKL issues Area Forecast Discussion (AFD) at Jun 19, 3:50 PM EDT---------------
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