LMK issues Area Forecast Discussion (AFD) at Dec 29, 12:36 PM EST
888
FXUS63 KLMK 291736
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
1236 PM EST Sun Dec 29 2024
.KEY MESSAGES...
* Wind Advisory 8AM to 7PM (EST) today, with wind gusts between 40-
55 mph expected.
* Another period of rain is forecast for Monday night into Tuesday.
By this time area rivers may be running high, though confidence is
low on whether or not there will be any flooding. Interests along
streams will want to monitor the waves of rain as they pass
through the district this weekend and early next week.
* A turn towards colder weather is outlooked for early and
especially mid-January.
&&
.UPDATE...
Issued at 904 AM EST Sun Dec 29 2024
Winds today...so far cloud cover and low level inversion has won out
on keeping wind gusts at bay. By late this morning and certainly
into the afternoon however, despite likely continued cloud cover,
expect that inversion to weaken. This change will allow more low-
level mixing and potential for any stronger winds aloft to mix down
to the surface. The pressure gradient from the departing low-
pressure system, now centered over SW IN, will tighten up over our
region. That surface low is expected to deepen, so despite pulling
away, we will see a good gradient over our area. The question mark
is how strong will the winds get? It's interesting to note that the
50th percentile winds from the 00Z Euro run had 58 mph peak gusts
over KLEX and 46 mph over SDF. All of that said, the mid shift
upgrade to a segmented Wind Advisory, with higher potential in the
Bluegrass region of KY, still looks good. Will be monitoring
radar wind profiles as well as upstream and Kentucky Mesonet wind
gusts through the day.
Rain chances today...radar mosaic shows that a lot of the dry slot
has filled in with very light rain returns. Have bumped up
measurable pops within this gap region. North/south band of
precip over IL/western KY is forecast to weaken on the south side
and lift NNE-ward as the whole storm system pulls NNE.
Rain chances this evening...deep residual low-level moisture along
with east/west bands of lift should mean scattered to potential
numerous shower development south of the I-64 corridor. Hi-res model
guidance are in pretty good agreement on this development, though
the question mark is where those bands develop. Have bumped up late
afternoon/evening rain chances to where the most confidence is, and
will continue this trend as we get closer to this next wave of
rainfall.
Gridded forecast already has been updated, and other products will
be out shortly.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 329 AM EST Sun Dec 29 2024
The sharp negatively-tilted upper trough will continue to pivot
across the central US today, carrying the attendant sfc low from the
mid-Mississippi River Valley through the lower Ohio Valley this
morning, and eventually onto Lake Erie by this evening. Warm air
advective widespread rain overnight has led to rainfall amounts
around an inch across portions of the area, which is being driven by
a healthy low-level jet overhead. This LLJ is evident on VAD wind
profiles, with KLVX showing southerly 55kt winds at 3k ft, and 65-
75kt winds between 5-6k ft. Peak wind gusts so far this morning are
in the low to mid 20 mph range, thanks to weak capping that has kept
most winds aloft, though some marginal momentum transfer has
occurred within the pockets of heavier rain rates. This LLJ has
funneled rich Gulf moisture into the lower Ohio Valley, maximizing
our 850mb moisture transport and increasing PW values up to 1.4
inches across central Kentucky. These PW values are at the max of
sounding climatology from BNA.
As the morning progresses, we'll see the sfc low continue to deepen
as it tracks from western Tennessee into southwestern Indiana,
lifting a warm front through the area. This will turn our sfc winds
from the southeasterly flow ongoing to a south-southwesterly flow
later this morning and afternoon. A dry slot is already evident on
regional radar mosaics over the western portions of Kentucky and
Tennessee. CAMs have a pretty good handle on this, and current radar
trends show the dry slot is now shifting into central Kentucky and
southern Indiana early this morning, which is beginning to diminish
precip coverage for the rest of today. A few isolated light rain
showers, or possibly even drizzle, will be possible through the
morning as the sfc low shifts off to our north.
The main concern for today will be the gusty gradient winds as the
sfc pressure gradient tightens significantly. Hi-res models also
hint at the possibility of a sting jet occurring late morning or early
afternoon as the cold conveyor belt wraps around the low and taps
into the dry slot across the area. Additionally, some minimal breaks
in the cloud deck over the dry slot could help slightly steepen
lapse rates as sfc temps warm into the lower 60s, and better promote
mixing down some of the high winds aloft. The HREF suggests some
breaks in the clouds could be possible after 12z, though confidence
remains low. Due to these concerns, and the possibility of a sting
jet bringing greater wind gusts, a Wind Advisory is warranted for
today from 13z this morning to 00z this evening. Wind gusts today
are expected to be between 40-55 mph, with the higher gusts east of
I-65 and in the Bluegrass region. 00z HREF suggests a 50% of
exceeding 50 mph gusts east of I-65 today. Additional light precip
is possible this afternoon as moisture wraps around the departing
sfc low, though should be light enough to limit any flooding
concerns after the morning heavier rain.
For tonight, gusty winds will be subsiding as the sfc low approaches
Lake Erie. CAMs seem to agree on lingering isolated to scattered
precip across south-central Kentucky this evening, but soundings
show a stable column and unidirectional flow. QPF remains light for
this last round of precip, with around a tenth of an inch possible.
Temperatures for tonight will remain mild, with 40s across the area.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 329 AM EST Sun Dec 29 2024
Monday...
Look for a brief dry period on Monday as transient upper ridging
traverses the region. Mild conditions continue with highs in the mid
to upper 50s for most.
Monday Night - Tuesday Night...
Rain chances return Monday night and Tuesday, and then linger into
Tuesday night as a surface low ejects out of the central Plains,
through our area, and then into the mid Atlantic states. Not nearly
as much moisture is expected with this system, but still expecting
fairly widespread coverage, especially across the northern half of
the CWA where categorical pops will continue. Storm total amounts
should range in the quarter to half inch range across our north.
Amounts less than a quarter inch should generally rule across the
southern CWA.
Temps during this stretch will feature mild values ahead of the
surface low. This results in Monday night lows only in the 45 to 50
degree range. Tuesday highs then top out in the low and mid 50s
ahead of the cold front. Colder air filters in Tuesday night behind
the front, with lows by Wednesday morning down into the low and mid
30s. At this point, it doesn't look like the cold air catches up to
the moisture, so no snow in the forecast at this point.
Wednesday - Thursday...
Looks like a cooler and drier pattern to start the New Year as post
frontal surface high pressure and unremarkable zonal flow aloft take
control of our pattern. Highs on New Year's Day and Thursday will
only be in the upper 30s and low 40s. New Year's night brings a
return of lows in the 20s.
Thursday Night - Saturday...
Confidence lower for the late week into the weekend timeframe.
However it does appear that a weak disturbance could bring some
light snow on Thursday night into Friday. Will keep chances for snow
in for that period, mainly across our northern half of the CWA.
Temps will struggle, but looks like another day with highs in the
30s for most. Saturday looks even colder, but dry as NW flow aloft
and Canadian high pressure dominate. Currently looking for Saturday
morning lows in the upper teens and low 20s, with highs Saturday in
the low and mid 30s.
&&
.AVIATION /18Z TAFS THROUGH 00Z TUESDAY/...
Issued at 1236 PM EST Sun Dec 29 2024
Light radar returns across most of the region this hour, with some
heavier returns approaching KHNB. Seeing some stronger wind gusts
close to the north/south axis of that rain band just west of KHNB,
along with near-IFR ceilings. Expect these will scatter out in the
next few hours, but stronger wind gusts should come through each of
terminals at the same time. The surface low producing these winds
will lift northeast away from the area through the afternoon,
gradually allowing winds to die back down. Some wrap-around showers
will develop late this afternoon and evening, mainly south of the I-
64 corridor, through close enough to warrant mention at KHNB and
vicinity mention at KSDF/KLEX. Those showers should only last a few
hours and then we should see cigs lower in the late overnight hours
and continuing for much of Monday morning.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Wind Advisory until 7 PM EST /6 PM CST/ this evening for
KYZ023>043-045>049-053>057-061>067-070>078-081-082.
IN...Wind Advisory until 7 PM EST /6 PM CST/ this evening for
INZ076>079-083-084-089>092.
&&
$$
UPDATE...RJS
SHORT TERM...CJP
LONG TERM...BJS
AVIATION...RJS
Source: LMK issues Area Forecast Discussion (AFD) at Dec 29, 12:36 PM EST (https://mesonet.agron.iastate.edu/p.php?pid=202412291736-KLMK-FXUS63-AFDLMK)
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