LMK issues Area Forecast Discussion (AFD) at Dec 27, 9:56 AM EST767
FXUS63 KLMK 271456
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
956 AM EST Fri Dec 27 2024
.KEY MESSAGES...
* A band of moderate rain will lift northeast across central KY and
southern IN this morning into early afternoon, bringing 0.25-0.50
inches of rain. A few areas in southern KY could see slightly more
than a half inch.
* The wettest period will be late Saturday into Sunday, with an
additional 1-2" of rain possible. Embedded thunder will be
possible Saturday evening but severe storms are not 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 956 AM EST Fri Dec 27 2024
A long column of rain from the Midwest to the central Gulf Coast is
spiraling ahead of low pressure over Missouri this morning. A 5H
speed max is crossing the Tennessee Valley along with strong low/mid
level winds: area radars are indicating 50kt flow around 4k'.
However, ACARS soundings at BNA and SDF show a strong inversion just
off the deck. Mesoanalysis reveals nil surface-based instability. As
a result, most of the winds have remained aloft, with the heaviest
downpours managing gusts generally in the 25-35mph range.
The forecast is in good shape as the morning rain pushes east,
leaving behind widespread low clouds and patchy sprinkles or
drizzle. Breaks in the clouds showing up from southwest Kentucky to
middle Tennessee could cause temperatures to overachieve slightly in
the Bowling Green area, but with clouds expected to quickly move
back in, will go ahead and keep the current forecast MaxT (BWG 60).
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 319 AM EST Fri Dec 27 2024
A lead upper level shortwave impulse is lifting northeast across
Arkansas early this morning, while an elongated wave traverses the
High Plains. Tremendous low-level moisture transport is occurring up
the Lower MS Valley just ahead of the Arkansas wave via a 50-55+ kt
southerly LLJ. A linear band of convection is ongoing over the Lower
MS Valley, where available instability is sufficient to support
thunderstorms. A bit further north, a band of moderate rain is
lifting northeast across western TN and far western KY.
This compact mid/upper level shortwave disturbance is forecast to
lift northeast across western KY and southern IN later this morning.
This will provide strong, deep lift and anomalous IVT over central
KY and southern IN as the 45-55 kt LLJ streams into the region.
Expect a band of moderate rain to push in from the southwest between
6-11 AM. Time of arrival is roughly 5-6 AM CST for the Bowling Green
region, 8 AM EST in Etown, 9 AM EST in Louisville, and 10-11 AM EST
for Frankfort/Lexington. The steady moderate rains will only last
about 3-4 hours at any one location, but some brief heavier rainfall
rates will be possible during that time. Average rainfall amounts
still look to range from a quarter inch to half inch. The higher
(roughly half inch or so) totals are expected across south-central
KY.
Behind this wave of moderate rain, rainfall coverage and intensity
will both drop considerably this afternoon and evening. A mid-level
dry slot spreads in from the southwest as the upstream shortwave
trough swings northeast from the central Plains to the Midwest.
However, low-level moisture will remain sufficient for widespread
clouds and patchy light rain or drizzle through the overnight hours.
Temperatures will run well above normal today and tonight with deep
SW flow on the warm side of the Midwest system. Highs today will be
in the mid/upper 50s, with lows tonight only falling into the
low/mid 50s.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 319 AM EST Fri Dec 27 2024
===== Saturday - Sunday =====
Deep southwesterly flow and strong WAA will keep us very mild
Saturday morning, with temperatures across our area likely in the
50s to begin the day, which will be around 10 degrees above our
normal highs for this time of year. Quite an impressive way to start
a December day to say the least. These temps will place us near
record warm mins for Dec 28, though there's still some uncertainty
of if we will actually break any records this time. This pattern
will result in temps in the 60s throughout the day, which could end
up being 20 degrees above normal.
We'll be in a strong WAA pattern thanks to deep southwesterly flow
funneling up from the Gulf and toward an upper shortwave and sfc low
that will be pivoting from the Upper Midwest to the Great Lakes.
Forcing will be better near those features, and should be fairly
weak across the lower Ohio Valley. Soundings show a shallow moisture
layer between the sfc and 850mb, which could be enough to squeeze
out a light shower or some sprinkles Saturday morning and afternoon,
but chances will be limited. NBM is much more enthusiastic for
measurable rain than the global solutions for Saturday morning, but
given the weak forcing and the shallow moisture layer, decided to
trim back PoPs to below 20% for the morning. The daytime hours may
end up drier as we will somewhat be located in between systems, but
a few isolated to scattered pockets of rain seem possible somewhere
in the area.
The main weather system of the long term comes Saturday night and
into Sunday as a sharp upper shortwave pivots from the southern
Plains into the lower Ohio Valley over the late weekend. We'll see
forcing increase significantly beginning Saturday evening, with LLJ
and moisture transport strengthening ahead of this system. This will
drive up our PW values, possibly reaching 1.3-1.4" across the
forecast area. This would be among the daily max from the BNA
sounding climatology database. Southerly 60kt LLJ will maximize our
moisture transport vector during the overnight hours, and when
combined with the mid-level forcing and upper level jet dynamics,
confidence in a widespread soaking rain event increases
considerably. The peak timing for widespread rain will be between
00z-12z Sunday, though additional precip activity will linger into
the daytime hours on Sunday as well.
The sfc low will track through the area Saturday night, which will
increase our wind shear parameters and promote a high shear/low CAPE
environment. Model soundings suggest any instability will likely be
elevated above a stable layer. As for rainfall amounts, a broad 1-2
inches is expected between 12z Saturday and 12z Monday. The bulk of
that rainfall is expected between 00z-18z Sunday however. The 00z
LREF shows a 15-20% probability of 24-hour rainfall exceeding 1.5"
of rain across south-central Kentucky by Sunday evening, with a 10%
probability of exceeding 2 inches in 24 hours across south-central
Kentucky. River information has not changed since yesterday, so as
mentioned in the previous discussion, the Hydrologic Ensemble
Forecast Service (HEFS) shows a 25-50% chance of the Green River at
Rochester creeping back up to flood stage by Tuesday.
===== Monday - Tuesday =====
Rain chances will exit from west to east Sunday night, and we should
be PoP-free by Monday morning. The upper flow will briefly become a
bit more zonal, with weak mid-level ridging overhead. However, clouds
will likely linger through the morning as we'll struggle to break
out upper level clouds, but we could see improvements by the
afternoon hours. Temps on Monday will be in the 50s, with south-
central Kentucky closer to 60. Monday should shape up to be a pretty
nice day for late December.
This dry weather period will be short-lived though, as another
shortwave appears to bring more rain to the region for Monday night
and into Tuesday. Temps will remain mild and above freezing, and
appears another chance for numerous to widespread rain is possible.
We'll be able to get deeper into the details in the coming days.
Rain chances will be on their way out late Tuesday night, but may
not entirely clear the area. Some folks in our east may be welcoming
the new year with some lingering rain, but chances are lower by
then.
===== Wednesday (New Year's Day) - Thursday ======
Dry weather looks to make a return for the first day of 2025 and
into Thursday as high pressure sets up across the southern Plains.
Trends continue to point toward colder temperatures for the
beginning of the new year.
&&
.AVIATION /12Z TAFS THROUGH 18Z SATURDAY/...
Issued at 646 AM EST Fri Dec 27 2024
Steady moderate RA spreading in from the SW this morning, with CIGs
and Vsbys expected to lower to MVFR. Brief IFR conditions also
possible today. Some TSRA has been noted in TN, but lightning
activity will diminish with NE extent. Did not include any TSRA
mention at BWG, but the chances are non-zero.
Steadier moderate to briefly heavy rain will only last 3-4 hours at
any one terminal, with precip coverage and intensity diminishing
greatly after ~18Z. MVFR CIGs will linger through the end of the
forecast period, and brief/patchy light rain or drizzle will be
possible this evening and overnight.
SE winds will increase to 10-15 kt this morning, with SSE winds
briefly becoming gusty this afternoon. Very marginal LLWS conditions
will be in place with a strengthening low-level jet overhead.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
UPDATE...13
SHORT TERM...EBW
LONG TERM...CJP
AVIATION...EBW
Source:
LMK issues Area Forecast Discussion (AFD) at Dec 27, 9:56 AM EST---------------
If I'm using your data in a way that is against your terms please email the team at "threatweb@pupswoof117.com"! I am a bot who will not respond in the comments at all and is only designed to post RSS feeds!
