JKL issues Area Forecast Discussion (AFD) at Aug 16, 12:17 AM EDT
744
FXUS63 KJKL 160417 AAC
AFDJKL
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1217 AM EDT Fri Aug 16 2024
.KEY MESSAGES...
- Humidity, along with the possibility of showers and
thunderstorms, will increase Friday and last into Saturday night.
- Below normal temperatures are expected Sunday through Wednesday
behind a cold front passage late Saturday night.
- Showers and thunderstorms will remain possible Sunday and
Monday, especially in the afternoon and early evening, with a
drying trend for Tuesday into Wednesday.
&&
.UPDATE...
Issued at 1217 AM EDT FRI AUG 16 2024
Quick update for some recent changes to current conditions.
Clouds and light rain have overspread portions of our eastern
zones as an area of light rain showers have built southward into
eastern Kentucky. This may have an impact on overnight lows in
the east, though initial lows may still be reached between the
exiting precipitation and clouds across our east in the coming
hour or so and the incoming round of showers and thunderstorms
that have been developing over central Kentucky during the past
hour or so. The hrrr seemed to have had this convection to our
west handled well. Thus will lean on it for much of the rest of
the overnight period. Updated grids and zones have been issued.
UPDATE Issued at 1033 PM EDT THU AUG 15 2024
Update this evening extends into tomorrow. Based on current
trends in temps and sky cover made some adjustments to the
overnight lows, including a non-diurnal trend with additional
cloud cover that will be overspreading the area over the next few
hours. Overnight lows will like be reached a little after
midnight, begin to level off, and then to increase a bit in the
hours leading up to dawn. Also, after getting a quick peak at the
0Z NAM, RAP, and hrrr run, model solutions are suggesting the
potential of some convection firing late tonight...in the hours
leading up to sunrise, generally between 4 and 8 am across much of
the forecast area. After this early morning convection, a second
round appears to take aim at the area through the late morning and
early afternoon. With the expected timing of the additional cloud
cover and convection, trended afternoon highs across our east and
southeast down a bit. However, there could be some late afternoon
partial clearing and the chance for some recovery of temperatures.
Thus only tweaked highs down just a few degrees over areas of
interest. Adjustments to the forecast and updated zones have been
issued.
UPDATE Issued at 700 PM EDT THU AUG 15 2024
Hourly temperatures have been falling a bit quicker than
previously forecast, so this trend will need to be watched closely
over the next few hours to determine whether or not tonights low
temperatures need to be adjusted. Used the most recent obs to
freshen up the hourly grids and establish new trends.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 350 PM EDT THU AUG 15 2024
The short term portion of the forecast looks to be quite active, as
a vigorous area of low pressure moves through the Great Lakes region
to finish out the week. The weather should remain quiet for most of
tonight, as the aforementioned system moves slowly our way. The
models differed a bit in their handling of this system and its
evolution and associated precipitation. The NAM12, NAMNEST, GFS, and
WPC guidance were all quite wet across our region, especially Friday
and Friday night, during frontal passage. The SREF and RAP models
were not as wet, and had larger time gaps between precipitation
episodes than the other four model mentioned above. With a general
consensus amongst a higher number of models, decided to go with the
wetter solutions at this time. The latest model QPF also differed a
bit across the area, with multiple bullseyes of higher amounts
showing up across our area Friday and Friday night, likely due to
the models difficulty in handling convection during that time.
However, with model soundings precipitable water values between 1.50
and just over 2 inches common across our area Friday and Friday
night, chose to go with the higher model QPF from both the NAM12 and
GFS solutions, with a swath of higher amounts across our southern
tiers of counties from the Hal Rogers Parkway southward to the
Tennessee border.
There is still a marginal risk of excessive rainfall across portions
or all of our forecast area Friday and Friday night, along with a
marginal risk of severe weather. The probability of severe storms on
Friday is quite low at this time, or roughly a 5% chance. As for the
chances of excessive rainfall that could lead to flooding, there is
currently a 5 to 14% chance of that occurring to end the week, which
is also quite low. As always, everyone should remain aware of the
danger posed by cloud to ground lightning that could occur with any
thunderstorm.
Warm and humid conditions will continue through the end of the week.
Highs on Friday will likely be several degrees cooler than what we
experienced today, but with dewpoints expected to increase into the
upper 60s and lower 70s on Friday, it will be quite steamy outside.
The high moisture levels will aid in thunderstorm formation and
maintenance as well.
.LONG TERM...(Saturday through Thursday)
Issued at 347 PM EDT THU AUG 15 2024
There is good agreement among the ensemble and deterministic
solutions for an upper low to push across the Great Lakes, with the
trough axis swinging through the Ohio Valley. This coupled with a
nearby frontal boundary will keep the weather active to begin the
period. Even so, the overall evolution in convection remains in
question, as you could begin the day at times with early morning
convection. This will certainly play a roll into how much
instability can be recovered in the afternoon hours. The EFI does
show decent signal for the climatologically significant
combination of CAPE and shear on Saturday, but when looking at
CAPE alone it was a much lesser signal. This means the shear
seems to be driving the values up more and the jet energy noted in
the various solutions is one that would support deeper layer
shear. Given the uncertainties mentioned, SPC did keep a marginal
risk going for Saturday. In terms of flooding, the concern here
would be places that can see multiple iterations of storms, so
overall threat right now is lower. Outside this expect near normal
temperatures (mid to upper 80s) Saturday depending on cloud
cover.
This trough axis will continue to swig through the area and lower
heights some as it does. This will keep the weather active through
Monday. The highest chances of rain will be Sunday when chances
of rain peak at around 50-90 percent particularly in the far
eastern parts of eastern Kentucky. By Monday, afternoon highs will
be running around 10 degrees below normal, with highs in the mid
to upper 70s in most locations.
A cold front or post frontal trough will user in much dryer air by
Tuesday. The PWATs will be running in the 25th percentile range for
this time of year at around 0.75 inches. There is good agreement on
an area of high pressure pushing into the Great Lakes providing
northerly flow at the surface and will lead a much cooler night
Tuesday into Wednesday morning. The dewpoints are expected to mix
out well under deep mixing on Tuesday and did adjust this down
given the usually too hot NBM deterministic toward the 10th
percentile. Given this lowered valleys into the upper 40s to lower
50s for overnight lows by Wednesday morning. This cooler valley
trend was also noted in the COOP MOS. We will begin to rebound
through the week to near normal for afternoon highs, with
overnight lows remaining in the low to mid 50s in most cases. The
other good news is it should be nice and dry Tuesday into Thursday
under the northerly flow and lower PWAT values.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 756 PM EDT THU AUG 15 2024
VFR conditions are expected as a predominant flight condition
through the bulk of the period. However, guidance suggests there
could be some short periods of high end MVFR conditions, mainly
associated with showers and especially thunderstorms that develop
across the area through the 10Z-18Z time frame as a slow moving
surface cold front approaches form the west. FROPA is not expected
through the area until Saturday night, or around 24 hours beyond
the end of the current forecast window. Winds will be light and
variable, around 5 kts or less until after sunrise, when a
southwest gradient wind between 5-10 kts develops ahead of the
approaching cold front. Winds could be gusty in the vicinity of
any thunderstorms.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...RAY
SHORT TERM...AR
LONG TERM...DJ
AVIATION...RAY
Source: JKL issues Area Forecast Discussion (AFD) at Aug 16, 12:17 AM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202408160417-KJKL-FXUS63-AFDJKL-AAC)
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