Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 141047
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
647 AM EDT Thu Mar 14 2024

...Updated Aviation Discussion...

.KEY MESSAGES...

* Near-record high temps today.

* There is a marginal risk for severe storms this afternoon and
  tonight. Best chance for storms will be during the overnight
  hours. Potential impacts include damaging wind gusts and large
  hail while spin-up tornado cannot be ruled out.

* Unseasonably cool Monday through Wednesday, with subfreezing
  temperatures possible each morning.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 328 AM EDT Thu Mar 14 2024

Synopsis...A shortwave trough, currently ejecting from the Desert
Southwest upper low, will push the surface low pressure over the
central Plains towards the Midwest and Great Lakes today, allowing
rain and storm chances to increase over the lower Ohio Valley. As of
now, there are two distinct periods when strong to potentially
severe storms can impact the forecast area. The first one is this
afternoon as earlier upstream convection grows upscale driven by a
wind speed max moving across the moderately unstable warm sector.
The second period will be at or shortly after midnight related to
the actual frontal dynamics in an less unstable and dynamic
environment.

Model Confidence/Evaluation...The risk of strong to severe storms
this afternoon is still conditional and therefore low confidence.
Although the thermodynamic and kinematic parameters are indicative
of an elevated severe threat, convection-allowing models are not
completely sold on storm initiation over southern Indiana and
northern Kentucky, leaving most of the organized convection to the
north or west. The second wave of storms on Thursday night appears
to have higher confidence of occurrence but chances of severe risk
might end up being lower, although not zero, given nocturnal
stability and subsequent weakening signal of convection depicted in
the hi-res guidance. Overall, the highest probabilities of severe
weather (wind/hail/tornado) are focused over the western and
northern sections of the forecast area as supported by the CSU and
Nadocast output.

Today...Southerly winds in the broad warm sector of the central
Plains storm system will continue theta-e advection over the lower
Ohio Valley which coupled with mostly unblocked solar radiation in
the morning will account for quick instability buildup and possible
near-record values in the afternoon (especially if storms stay
north). Surface winds will gradually increase in the morning and
eventually become gusty in response to the incoming 40- to 45-knot
southwesterly low level jet. Overnight upstream convection has
started to congeal into several linear features while eastward. The
ongoing upscale growth will continue through the morning hours while
approaching the Middle Ohio Valley. As mentioned above, there is
much uncertainty in how far south the system will extend, but if it
does, it will tap into a moderately unstable and sufficiently
sheared environment capable of supporting deep, organized
convection. If this conditional threat realizes, then all severe
threats are on the table with an emphasis on isolated damaging winds
and large severe hail. Nonetheless, any cellular element might
quickly display rotating updrafts and an enhanced tornado risk based
on STP and SCP values. Lastly, the afternoon convection (independent
of where it occurs) will likely produce an strong convective outflow
that will serve as the focus of further redevelopment later in the
evening and tonight.

Tonight...Second wave of storms will arrive around midnight or
shortly after ahead of the weakening frontal boundary. Consensus of
CAM models, including several past runs of the GFDL SHIELD, have
been to focus storms along a couple of linear features: one oriented
west to east associated with earlier convective outflow and a second
one (potentially stronger) diving from western Kentucky to the
Tennessee Valley force by residual mid-level frontogenesis. Although
the environment will not be as supportive for convective
maintenance/development as earlier in the afternoon, sufficiently
strong cores plus cold pool dynamics amid a few hundreds of ML CAPE,
upper jet lifting, and decent deep-layer shear will support a
marginal risk of damaging winds and isolated, brief spin-up
tornadoes for virtually the whole event

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 328 AM EDT Thu Mar 14 2024

Active weather will continue into Friday as we begin the day with
the cold front near the Ohio River. The boundary will be laying out
almost parallel to the flow aloft, so expect its southward progress
to be slow. Better forcing and deep moisture will be focused more
across the Tennessee Valley by this point, so the severe threat
should have departed to the south. However, there is still just
enough lift along and ahead of the front to support scattered to
numerous showers through the day Friday, and even some embedded
thunder. Cloud cover, precip, and cold advection will limit temp
recovery on Friday and keep us in the 60s.

Dry weather for the weekend but we will transition to a much cooler
pattern as a deep, stacked low pressure system makes its way from
Lake Winnipeg on Friday afternoon to southern Quebec on Sunday,
carving out a broad eastern CONUS trof. Fast NNW flow over the
Plains on Sunday will allow unseasonably cold air to spill
southward, spreading into the Ohio Valley in earnest early next
week. Tuesday will be the coldest morning with sfc ridge axis draped
across Arkansas and Tennessee, and temps in the 20s for most of
Kentucky and southern Indiana. Subfreezing temperatures are likely
each morning Monday through Wednesday. Daytime temps will really
struggle on Monday with highs in the lower/mid 40s, a solid 10-15
degrees below normal. A gradual moderating trend will follow as we
go through the week.

&&

.AVIATION /06Z TAFS THROUGH 12Z FRIDAY/...
Issued at 646 AM EDT Thu Mar 14 2024

Impacts/Confidence:
- High confidence in gusty SW winds of 20-25 knots today.
- Low confidence in storm chances this afternoon.
- Increasing confidence in MVFR/IFR conditions tonight with storms.

Discussion...Prevailing VFR conditions for most of the forecast
period except with heaviest showers and/or storms. Expect quiet
weather during the morning and part of the afternoon as a low
pressure system and cold front moves towards the Ohio Valley.
Strengthening of the low-level flow will promote gusty SW winds by
midmorning and through the afternoon. There is a conditional threat
of isolated, strong storms this afternoon, so additional adjustments
could be needed at HNB and SDF if it actually occurs. Better
coverage, and therefore confidence, exists with a second round of
storms tonight with MVFR/IFR visibilities as the main impact to all
terminals.

&&

.CLIMATE...
Issued at 329 PM EDT Wed Mar 13 2024

================== Potential Record Temperatures ==================

             Thursday 3/14/2024
          Max T Fcst/Record (Year)

Louisville:       78/82     (2012)

Bowling Green:    79/82     (2012)

Lexington:        77/81     (1973)

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.

&&

$$

SHORT TERM...ALL
LONG TERM...RAS
AVIATION...ALL
CLIMATE...DM/ALL


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