LMK issues Area Forecast Discussion (AFD) at Mar 4, 2:59 PM EST624
FXUS63 KLMK 041959
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
259 PM EST Tue Mar 4 2025
.KEY MESSAGES...
* Showers and strong wind gusts expected this evening. Isolated
thunderstorms and isolated wind damage are possible.
* Wind gusts this evening through Wednesday may occasionally reach
40 to 55 mph. Most likely time for strong gusts will be this
evening and again Wednesday afternoon.
* Colder with possible rain mix to snow Wednesday afternoon into
Wednesday night.
&&
.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 258 PM EST Tue Mar 4 2025
Cloud cover has started to fill in at this hour, and we are finally
starting to see some better dew point recovery as the low level jet
becomes more established over our area. As a result, wind gusts have
continued to steadily increase and have now had a handful of ASOS
and KY Mesonet obs reporting some gusts in the 40-43 MPH range. Wind
Advisory was started early, so expect these gusts to occasionally
occur through the remainder of the afternoon.
Still expecting the most intense and widespread gusts for today to
occur 1.) with the onset of precipitation/saturation of the dry low
level column, and 2.) with the more upright showers/thin line
convection later tonight. Decided to bump the magnitude of the Wind
Advisory up to 45 to 55 MPH to account for HREF data suggesting
fairly high probabilities for wind gusts over 50 MPH. Will say that
we continue to think this is overdone, as it was way overdone this
morning, and it has had trouble in the past with overly strong
nocturnal low level jets. The LREF/NBM wind gust data seem more in
line with forecast soundings and Bufkit momentum transfer values, so
will continue to lean more toward that side of the data envelop.
This keeps us in the Advisory range, but will certainly be
monitoring upstream obs/trends as we get into the heart of the low
level jet core. The LLJ core looks to peak over our area between 23z
and 07z, with a magnitude around 70-80 knots. Forecast soundings
continue to show some stability in the lowest levels, which should
help us from realizing a lot of that wind energy. That being said,
certainly can't rule out some pockets of damaging wind if the
strongest showers or a storm are able to bring the higher momentum
winds down to the surface.
SPC Marginal Risk basically follows our chances for thunder, but the
reality is that a damaging wind gust could occur anywhere in our CWA
if that air is brought down. Again, we don't expect this to occur
given the low level stable layer, but also can't rule it out. It is
possible that a short fuse High Wind Warning or some convective
warnings may be needed if we start to observe severe gusts or hear
about damage.
After the main line of convection passes and the worst of the LLJ
core pushes northeast, we will likely see a relative lull in the
strongest gusts. This will also coincide with the dry slot, which
luckily will mostly occur in the nighttime/pre-dawn hours. Around
and shortly after sunrise, expect the winds to kick up again into
the 40 to 50 mph range as steepening low level lapse rates mix back
into the lingering low level jet core aloft still maintaining values
in the 40-45 knot range. As mentioned before, elected to keep the
Wind Advisory running through the whole duration with the
acknowledgement that there will be some lulls.
Numerous showers should develop and persist as the wrap around
moisture and steepening low level lapse rates commence. As a result,
have some high pops/low qpf values in for Wednesday. Temps drop
through Wednesday, and by late afternoon/early evening values in the
30s could support some rain/snow or just plain snow showers. Not
expecting any notable impacts outside of some rooftop dusting as we
head into the evening hours.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Issued at 258 PM EST Tue Mar 4 2025
Wednesday Night...
The aforementioned low pressure system and associated deep upper
troughing will continue to move off to the northeast Wednesday
night. As cold air wraps around the backside of the low, snow will
begin to mix with rain Wednesday evening through most of the
overnight period. There is good saturation in the DGZ, although
there is a lack of instability that will prohibit heavy snow or
large flakes. A Trace to a few tenths of an inch of snow will be
possible. Accumulations on elevated surface and grassy areas are
possible. Low temperatures on Thursday morning are expected to fall
into the upper 20s and low 30s.
Thursday - Thursday Night...
Ridging aloft and surface high pressure will build in on Thursday,
allowing skies to clear and winds to steadily decrease. Ample
sunshine and WAA will help to bring high temperatures into the upper
40s and low 50s. In the overnight period, winds will be calm to
light and skies will steadily increase from west to east. Low
temperatures are expected to fall into the upper 20s and low 30s.
Friday - Saturday Morning...
The upper pattern will become more zonal in the latter part of the
week. A weakening shortwave trough is expected to eject out of the
central Plains and into the Ohio Valley, bringing a weakening
surface low pressure system with it. Placement and strength of the
surface low remains uncertain, and this will determine how much
precip we can get out of it. If the low tracks over southern Indiana
we will see ample southwesterly flow and a 45-55kt LLJ ushering in
better moisture. Would expect to see temperatures overachieve into
the 60s, breezy surface winds, and showers along and ahead of the
cold front. If the low tracks further south over Kentucky,
isentropic lift will bring widespread stratiform rain and near
normal temperatures. With either solution, there is a chance for
some snow to mix with rain on the backside of the low. Snowfall
amounts would be a Trace to a few tenths of an inch. Will continue
to track model trends of the next few forecasts.
Saturday - Early Next Week...
A closed upper low over the desert southwest will begin to move east
over the southern Plains and into the southeastern CONUS. This
system has trended south over the last few runs. If this stays to
the south, only our southern most counties will be scattered PoPs.
If it trends north over the next few days, the entire region will
see more widespread PoPs.
After this system moves through, high pressure is forecasted to
build in behind, bringing mild and quiet conditions to the region.
&&
.AVIATION /18Z TAFS THROUGH 00Z THURSDAY/...
Issued at 1258 PM EST Tue Mar 4 2025
Currently seeing gusty SE to S winds between 25 and 35 mph with
variable mid and upper clouds. Expect wind gusts to continue now
through this TAF cycle, with the strongest gusts this afternoon
through late evening, and then again mid morning tomorrow through
the afternoon.
Expecting mostly VFR conditions, however do expect some periods of
MVFR vis this evening into the overnight when the heaviest showers
fall. We should recover back to VFR again through the pre-dawn
hours. Did mention a brief period of LLWS when the low level jet
peaks around 55-65 knots around 2 K feet. This intense speed shear
could cause compression issues in the traffic pattern at SDF, and
we'll see around 30 degrees of veering between the surface and 2k
feet.
Wrap around moisture and precipitation then sets in around sunrise
to mid morning tomorrow.This will likely yield some MVFR ceilings
once established. In addition, gusty SW winds between 40 and 50 mph
are expected from mid morning onward.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Wind Advisory until 7 PM EST /6 PM CST/ Wednesday for
KYZ023>043-045>049-053>057-061>067-070>078-081-082.
IN...Wind Advisory until 7 PM EST /6 PM CST/ Wednesday for
INZ076>079-083-084-089>092.
&&
$$
SHORT TERM...BJS
LONG TERM...SRW
AVIATION...BJS
Source:
LMK issues Area Forecast Discussion (AFD) at Mar 4, 2:59 PM EST---------------
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