JKL issues Area Forecast Discussion (AFD) at Mar 26, 5:20 PM EDT328
FXUS63 KJKL 262120
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
520 PM EDT Wed Mar 26 2025
.KEY MESSAGES...
- A couple of relatively weak waves will cross the area through
this evening with successive rounds of isolated to scattered
showers - mainly affecting northeast portions of the state.
- Seasonal temperatures are expected through Thursday, followed by
a significant week-end warming trend.
- Multiple rounds of showers, and perhaps thunderstorms, are
possible this weekend within the warm sector of a strong storm
system moving towards the Greater Ohio River Valley.
&&
.UPDATE...
Issued at 1122 AM EDT WED MAR 26 2025
Late morning obs have been blended into the forecast. Latest model
guidance looks unsupportive of precip today, POP has been
reduced below the 15% (rounds to 20%) threshold for forecast
inclusion.
UPDATE Issued at 720 AM EDT WED MAR 26 2025
No significant changes were made to the forecast with mainly just
the inclusion of the latest obs and trends for the T/Td/Sky grids,
though did add in some fog across the north for valley locations
through 13Z. These minor adjustments have been sent to the NDFD
and web servers along with a freshening of the zones and SAFs.
&&
.SHORT TERM...(Today through Thursday)
Issued at 500 AM EDT WED MAR 26 2025
08Z sfc analysis shows a weak area of high pressure moving over
Kentucky this morning. At the time of writing, it is starting to
enter the JKL CWA proper. This system is shunting lower clouds
and sprinkles out of the far eastern parts of the state, allowing
for some late night radiational cooling. Under the clearing pre-
dawn skies, we are starting to see some fog show up on satellite.
These conditions will probably result in some scattered frost
formation - mainly for northern parts of the JKL CWA. Temperatures
currently vary from the mid 30s northwest and in some of the
sheltered valley to the mid 40s on the ridges through the
southeast. Meanwhile, amid light northwest winds, dewpoints range
from the low and mid 30s northwest to the upper 30s in the south.
The models, and their individual ensemble suites, remain in pretty
good agreement aloft through the short term portion of the
forecast. They all depict Ohio Valley troughing at 5h slowly
pulling east out of the region. As this happens, a couple of mid
level impulses will pass through eastern Kentucky with the first
arriving later this morning and another on its heels towards
evening. Each of these will bring a touch of extra lift to the
area before the trough and its cyclonic flow relaxes allowing 5h
heights to start to rebound. Tonight, the pattern progresses from
northwest flow trailing the eastern trough to one reflecting the
approach of an area of weakness amid a Southern Plains ridge.
Energy from this weak troughing then will work eastward toward
Kentucky with an impact on our sensible weather expected by that
evening. The still very small model spread aloft again supported
using the NBM as the starting point for the forecast grids through
the period. Did make some adjustments to incorporate more CAMs
guidance into the PoPs today through Thursday and also to include
more terrain based distinctions in temperatures early this
morning and again tonight.
Sensible weather features amorphic sfc pressure systems mostly
ineffective at driving the weather machine over eastern Kentucky
through the period. We will see general high pressure today unable
to hold off patches of lower clouds passing through along with
some scant chances of showers, but mostly just sprinkles
throughout the day amid cooler than normal conditions for the
entire area. Tonight, skies will be mostly clear for much of the
time - allowing for some radiational cooling and frost
development. However, thicker and lowering clouds do arrive late
in the night from the northwest. This means that sprinkles will be
possible into the morning on Thursday. The warm front from the
next system should start to become a bit more active to the west
of the area Thursday morning before translating east during the
afternoon bringing better chances of showers but not a whole lot
in the way of QPF. The clouds and late arriving pcpn on Thursday
will also work against an impending warm up - at least for one
more day - keeping high temperatures near normal.
The changes to the NBM starting point consisted primarily of
adding some extra terrain distinctions to temperatures early this
morning and again tonight. As for PoPs, again mainly tweaked them
per timing and coverage details from the CAMs consensus
throughout the period.
.LONG TERM...(Friday through Wednesday)
Issued at 520 PM EDT WED MAR 26 2025
By the end of the week Friday, the ridge in the Pacific Northwest,
that had been prevalent will begin to flatten out as a result of a
couple shortwaves passing both north and south of a rather
stationary offshore low. Further east, the warm front that is
currently modeled over Eastern Kentucky for Thursday will continue
pushing north and east into the Upper Ohio Valley, by Friday.
While the above unfolds, moisture from a weak low in the Gulf
will continue to come together.
Across Kentucky, RH fields show drier air intruding into the lower
levels in the morning following the departure of the warm front into
the Upper Ohio Valley. There may be some elevated showers that
linger aloft, however low levels begin to dry out. Continuing to
look at RH fields aloft as well as wind profiles, a shortwave
located in the OK/AR region of the Lower Mississippi Valley begins
to propagate northward into western portions of the Tennessee and
Ohio Valleys. Persistent southwest flow through the day will
moisten the air column aloft and near the surface some. In
addition, some limited instability will be available from this
persistent southwest flow. MUCAPE values of 500-600 J/kg along
with sufficient shear should be adequate to support the
development of a thunderstorm or two. In addition, model soundings
suggest low freezing levels (below 10K feet). This could yield
some small hail from any of these storms were to develop during
the afternoon. Instability is modeled at its greatest during peak
diurnal heating, around 21Z or so. A small warm nose, or cap
aloft, may be a limiting factor in thunderstorm development, yet
a slight chance of thunderstorms remains in the forecast for
Friday afternoon, tapering off sharply after 00Z. Persistent
southwest flow through the day will allow for temperatures to
creep into the upper 70s, to near 80 in places. With persistent
cloud cover acting as an insulator as well as southwesterly winds,
temperatures will remain elevated overnight, ranging around 60.
Current model solutions have the upper level low over the Lower
Mississippi Valley propagating into the Ohio Valley, west of the
area during Friday, as streamlines are flow from the SSW towards
the NNE. Midday Saturday, there is some shifting in the
streamlines to more of a southwest direction, and this is what
will allow for the propagation of moisture from the MS/AL area to
saturate the mid and lower levels conducive to producing shower
activity. As a result a slight chance of showers are expected to
develop later in the afternoon Saturday, from west to east,
becoming likely in the evening and overnight hours. There will
again be some limited instability, mainly west of the I-75
corridor and along the I-64 corridor. This is the general area
that can see a thundershower or two during the late evening and
overnight hours Saturday. Temperatures through the day Saturday
are forecast in the mid to upper 70s, while it will be raining at
night, cloud cover will again act as an insulator, with
temperatures dipping into the upper 50s to low 60s.
Shifting focus for a second, during the early morning hours
Saturday, while the above takes place across portions of the
Mississippi, Tennessee and Ohio Valleys, further west, an embedded
shortwave in the flow of a discrete negatively tilted trough will
make its way out of the Pacific Northwest through the Northern
Plains Saturday evening, and intensify over the Middle Mississippi
Valley. During the day Sunday, this upper low is modeled to move
into the Upper Great Lakes, and northern portions of the Ohio
Valley; all while a trailing cold front extends out south and west
of the lows center, back through the Mississippi Valley.
Prefrontal showers and thunderstorms will continue across Eastern
Kentucky, with a favorable environment for thunderstorms. With MUCAPE
of 700-1000 J/kg, shear of 35-45 kts, and decent mid level lapse
rates, all hazard types of severe weather are theoretically still
on the table if storms are able to tap into it. A stronger warm
nose, or cap aloft will make it difficult for storms to initially
break through and tap into the instability. CIN is also modeled to
be present in the afternoon adding further challenges to storms
trying to break through the cap. The best lift available comes
later in the evening, after much of the instability has begun to
dissipate. Better forcing is further west and south in Western
Tennessee an Western Kentucky. The frontal passage looks to occur
in the overnight hours which also mitigates threats of spinups
along the line, by limiting instability. Dewpoints are modeled to
be in the 50s to near 60 all day. This may introduce a low flow
flood threat, especially in training thunderstorms, or embedded
thunderstorms with higher rain rates. Southwest winds through the
day will allow for temperatures to climb into the upper 70s to low
80s.
Showers and a chance of thunderstorms will continue through Sunday
night through the afternoon Monday, as the trailing cold front
associated with this upper level low slowly moves off to the east.
Winds will veer from a southwesterly wind to a northwesterly
direction introducing cold air advection in the afternoon.
Temperatures will be cooler as a result, ranging from the lower 60s
to upper 60s from north to south. Shower chances will diminish
heading into the evening. Temperatures will cool into the lower 30s
across the Bluegrass, with the rest of the area cooling to the upper
30s to lower 40s. With the coldest spots being in the Bluegrass,
frost will be possible, though winds and cloud cover may be
mitigating factors.
Tuesday, lower shower chances were retained in the forecast because
of a little shortwave that passes across the upper Ohio Valley, but
model indications suggest this could trend drier. Cold air
advection will continue Tuesday, leading to temperatures reaching the
mid 50s to lower 60s. By Tuesday evening weak ridging will allow for
winds to veer to an east southeast wind. Temperatures will cool into
the low to mid 40s.
Wednesday, a large disparity in model spread leads to lower
confidence in whats to come. Two of the predominant models have
complete opposite pattern structures so confidence remains low on
what may occur.
&&
.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
ISSUED AT 135 PM EDT WED MAR 26 2025
VFR conditions and winds less than 10 kts are forecast through the
period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...HAL/GREIF
SHORT TERM...GREIF
LONG TERM...GINNICK
AVIATION...HAL
Source:
JKL issues Area Forecast Discussion (AFD) at Mar 26, 5:20 PM EDT---------------
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