LMK issues Area Forecast Discussion (AFD) at Mar 14, 6:57 AM EDT ...Updated Aviation Discussion...
322
FXUS63 KLMK 141057
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
657 AM EDT Fri Mar 14 2025
...Updated Aviation Discussion...
.KEY MESSAGES...
* Unseasonably warm and windy today with record-challenging high
temperatures.
* Strong to severe thunderstorms are expected to approach the area
late this evening, reaching the area after midnight tonight. The
greatest severe threat will be west of the Interstate 65 corridor.
Damaging winds and brief tornadoes will be the primary severe
hazards tonight.
* Widespread showers and thunderstorms can be expected Saturday
afternoon and night. Locally heavy rain may cause flooding
problems in some areas by evening, especially in central Kentucky.
There will also be a chance of severe storms, with all hazards
possible.
* Non-thunderstorm winds will be strong and gusty this afternoon
through Saturday evening. A Wind Advisory is in effect.
&&
.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 348 AM EDT Fri Mar 14 2025
It is another quiet morning across central KY and southern IN, with
mostly clear skies being observed on latest nighttime microphysics
satellite imagery. There is a 15-20 degree ridge/valley temperature
split in latest obs, with values ranging from the mid 40s to near 60
degrees as of 07Z. With sfc pressure falls occurring west of the
Mississippi in association with tonight/tomorrow's system, a light
SE breeze has begun in more well-mixed locations. Between now and
sunrise, temperatures should fall a few more degrees with scattered
high clouds beginning to spread across the area from west to east.
Today will be an unseasonably warm and windy day across the area
with deep SW flow aloft. This is all thanks to a negatively-tilted
upper shortwave which will quickly eject from the Four Corners
region into the central Plains later today. Ahead of this system,
upper diffluence will support lee cyclogenesis across the central
high Plains later today, with central sfc pressures expected to drop
from around 988 mb at this hour to the mid-970s by this afternoon.
In response to pressure falls across the Plains and Mississippi
valley today, southerly winds will steadily increase through the day
across the Ohio Valley. By mid-to-late afternoon, BUFKIT momentum
transfer shows the potential for 25-30 kt gusts, especially along
and west of I-65. This southerly near-sfc flow will assist
temperatures in climbing through the day, and the current forecast
calls for the warmest highs of the week (78-83 across the CWA),
threatening daily records. Scattered high clouds should move across
the area today, and increased boundary layer moisture may also
result in a scattered cu field in the late morning and afternoon
hours. While there is not much of a trigger for convection during
the daytime hours today, some hi-res solutions do show a few blips
later today, and there will be increasing instability. While a
shower can't be ruled out today, confidence is low and coverage
should be minimal, so we'll keep silent PoPs (<15%) going.
By mid-afternoon, convection is expected to fire along a NNW-SSE
oriented boundary in the central Plains near the I-29/I-49
corridors. Current hi-res progs show quick upscale growth into a
severe QLCS across the mid- and upper-MS valley late this afternoon,
with the system moving to the east-northeast through the evening
hours. Across our area, breezy southerly winds will continue after
sunset, with dry weather expected through midnight. Since only
scattered upper sky cover is expected during the immediate post-
sunset hours, it is possible that some boundary layer stability may
develop, limiting wind gust potential this evening and overnight.
However, given a 70+ kt 850 mb jet and 50+ kt of southerly flow 1-2
kft off the ground, think the wind advisory is still reasonable to
advertise the potential for sporadic stronger gusts.
The southerly LLJ will also help to draw increasing moisture up from
the Gulf, and when coupled with mid-level height falls, should
result in a pool of instability most prominent west of the I-65
corridor. As the aforementioned severe QLCS approaches our area from
the west, a narrower channel of higher near-sfc moisture (low 60s
sfc dewpoints) is expected to be drawn northward into western KY and
southwest IN, increasing sfc-based instability. Several hi-res progs
show more discrete convection developing just ahead of the main
line, which would be expected given deep-layer shear vectors which
are more perpendicular to the convective line. Any multi-cells or
supercells would carry an increased potential for tornadoes,
especially given the extremely high amounts of shear and helicity
present. As convection moves farther east into KY and IN, it will
encounter a gradually more hostile environment, as the corridor of
greatest near-sfc moisture will struggle to push east of I-65. As a
result, convection should become more elevated, limiting (but not
completely eliminating) the severe potential. With such strong flow
aloft, collapsing storms with strong downdrafts could easily bring
severe-level wind gusts to the surface, even when convection is
elevated.
With all this being said, the message from general thinking for
tonight's wave of storms is relatively unchanged. The greatest
potential will be west of the I-65 corridor. All severe hazards are
on the table, though damaging winds and spin-up tornadoes will be of
primary concern, with hail mainly confined to any supercells which
develop. Once you get to around the I-65 corridor, straight-line
wind should become the predominant threat given decreasing sfc-based
instability. Timing is a bit slower than the previous forecast --
would expect storms to hold off until after midnight, approaching
our western CWA border by 05-07Z and getting to the I-65 corridor by
around 08-10Z. If storms reach the I-75 corridor, it wouldn't be
until the immediate pre-dawn hours on Saturday.
&&
.LONG TERM /TONIGHT THROUGH THURSDAY/...
Issued at 656 AM EDT Fri Mar 14 2025
Saturday - Saturday night:
By late Saturday morning surface low pressure will develop southwest
of Memphis just ahead of a 500mb speed max rounding the base of the
upper trough. This surface low will move northeastward along a cold
front, into Kentucky by mid evening and then into the upper Ohio
Valley late Saturday night. Deep moist flow will pull moisture and
warm cloud depths northward from the western Gulf to the Great
Lakes. While the deepest moisture and richest 850mb theta-e air will
be found over Mississippi and Alabama, PWATs around 1.25-1.45" can
be expected in southern Indiana and central Kentucky, which would be
near the daily climatological max. A large area of widespread
showers and storms will develop in conjunction with this storm
system from the central Gulf coast to the eastern Great Lakes.
Though general QPF is in the 1.0-2.5" range, which most areas would
be able to handle if evenly spread out from Saturday afternoon
through Saturday night, it looks like streaks of heavier rainfall
amounts can be expected with training storms. This idea is supported
by RAP/NAM/WPC QPF depictions showing narrow stripes of 3-4" and
HREF LPMM also indicating narrow corridors of higher rainfall
amounts. The region continues to be in a Slight Risk for excessive
rainfall from WPC.
While confidence in widespread and occasionally heavy rainfall is
relatively high, confidence in the chances of severe storms on
Saturday is lower. While there will be plenty of shear associated
with this energetic late winter/early spring system, instability
appears to wane as the widespread clouds and rain move in during the
afternoon and evening. Plan-view model CAPE fields show SB/MUCAPE in
place during the morning hours, and soundings show some positive
area (though generally "tall & thin"), but the instability and mid-
level lapse rates weaken by the time the afternoon/evening round of
convection moves in. Still, with a coupled upper jet structure,
strong flow, strong shear, and very strong low level helicity, we
can't let our guard down for the possibility of severe storms
Saturday afternoon and early evening with all severe hazards in
play.
Another complicating factor that will have an effect on how much
instability can be achieved is how much cloud and rain will be
present Saturday morning. Tonight's storms may still be moving out
of eastern sections of central Kentucky shortly after sunrise
Saturday morning, and atmospheric cross-sections suggest nearly
overcast skies throughout the morning hours.
Non-thunderstorm surface wind gusts of 30 to 40 mph can be expected
Saturday and Saturday night, with occasional gusts over 40 mph
possible, especially east of I-65 during the evening hours as a
narrow 925mb jet streaks from middle Tennessee to southern Ohio.
Sunday:
Scattered lingering showers can be expected Sunday morning ahead of
the upper trough axis that will pass overhead Sunday
afternoon/evening. Any additional QPF will be very light...on the
order of a tenth of an inch or less. High temperatures Sunday will
be about 15-20 degrees cooler than Saturday behind the departing
storm system, with afternoon readings peaking in the 50s.
Sunday night - Tuesday night:
This period will be quiet as high pressure moves along the Gulf
Coast and into the Carolinas. After low temperatures Monday morning
around the freezing mark, readings will rebound as we get into
return flow, with afternoon highs on Tuesday in the 70s.
Wednesday-Thursday:
An area of low pressure advancing from the Midwest to the Great
Lakes will swing a cold front through the Ohio Valley, most likely
Wednesday night. Not a lot of moisture or instability is associated
with this system, so for now it looks like QPF will be light and
severe weather unlikely.
&&
.AVIATION /12Z TAFS THROUGH 18Z SATURDAY/...
Issued at 656 AM EDT Fri Mar 14 2025
Winds will steadily increase out of the south through the daytime
hours today, with occasional gusts in excess of 25 kt expected this
afternoon. VFR conditions are expected through at least 15/06Z, and
most of the forecast changes today are for increasing wind gusts. Do
expect wind gusts to briefly decrease around sunset tonight thanks
to some near-sfc stability. Confidence in wind speeds/gusts
decreases overnight, as a 70+ kt LLJ moves over the region. If any
sites can mix stronger winds down, gusts in excess of 30 kt are
possible, though this is highly uncertain.
Between 06-12Z tonight, a line of strong thunderstorms is expected
to approach the region, moving from west to east during the pre-dawn
hours. Within these storms, LIFR/IFR visibilities, reduced ceilings,
and wind gusts of 40+ kt will be possible. For this forecast, will
use TEMPOs for TSRA at HNB/SDF/BWG, and PROB30 where confidence is
lower at LEX. TSRA should barely reach RGA by 12Z Saturday, so we'll
keep mention out of the forecast for now.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Wind Advisory from 5 PM EDT /4 PM CDT/ this afternoon to 8 PM
EDT /7 PM CDT/ Saturday for KYZ023>043-045>049-053>057-
061>067-070>078-081-082.
IN...Wind Advisory from 5 PM EDT /4 PM CDT/ this afternoon to 8 PM
EDT /7 PM CDT/ Saturday for INZ076>079-083-084-089>092.
&&
$$
SHORT TERM...CSG
LONG TERM...13
AVIATION...CSG
Source: LMK issues Area Forecast Discussion (AFD) at Mar 14, 6:57 AM EDT ...Updated Aviation Discussion... (https://mesonet.agron.iastate.edu/p.php?pid=202503141057-KLMK-FXUS63-AFDLMK)
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