LMK issues Area Forecast Discussion (AFD) at Nov 14, 12:42 AM EST ...Updated Aviation Discussion...258
FXUS63 KLMK 140542
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
1242 AM EST Thu Nov 14 2024
...Updated Aviation Discussion...
.KEY MESSAGES...
* Widespread moderate rain tonight, with locally heavy rainfall
at times. Average rainfall totals of 1-2", with swaths of 2-3"
likely causing minor flooding issues.
* Breezy winds, cloudy skies, and light rain on Thursday with
slight chance of thunder for the Bluegrass area.
* Dry through the weekend. Temperatures remaining at or above
normal.
* Shower/storms are likely by Tuesday with a transition to a much
colder pattern for the later half of next week with light wintry
precipitation likely.
&&
.UPDATE...
Issued at 816 PM EST Wed Nov 13 2024
Two waves of showers, with embedded thunder have been working across
central KY and southern IN this evening. Highest rain amounts so far
have been over Dubois, Perry, Crawford, Harrison, Floyd counties in
Indiana with Hancock, Ohio, Breckinridge, Meade, Butler, Logan,
Grayson to Hardin counties in KY where amounts have ranged between
an inch to an inch and a half with a few isolated locations around 2
inches as of 8pm EST. A flood advisory was issued for where we saw
some of the highest rain amounts with additional rain already
working in across the area.
While wave number one was located along the I-75 corridor, wave two
was working over and along the Ohio River over north central KY and
southern IN. An additional half inch to possibly an inch is
possible. There has also been a few embedded rumbles of thunder
thanks to the strong 45-50kt LLJ and just a couple hundreds of
MUCAPE. On top of that we are seeing an axis of 1.4 to 1.5" PWAT
values co-located with the LLJ as it surges over the area over the
next couple of hours. While the overall forecast remains on track,
updated the grids to extend the mention of thunder a little farther
north towards north central KY and the Ohio River, including the
Louisville metro. Given the high PWAT values, any convective showers
could produce a brief period of heavy rainfall, leading to ponding
on roadways and even localized urban street flooding. Will issue
updated products after publishing this update.
&&
.SHORT TERM /THROUGH FRIDAY/...
Issued at 258 PM EST Wed Nov 13 2024
Synopsis...Intense mid-level shortwave trough will move across the
region tonight into tomorrow while an upper-low starts to develop in
its core thanks to a 250-mb jet entering the upstream side of the
wave. At the low levels, occluding surface low translates from the
Mid Mississippi Valley to the Lower Great Lakes as a cold front sags
eastward towards the Ohio Valley. Low-level mass response will
support a 50-knot jet bisecting the forecast area leading to
enhanced moisture influx and convergence.
Rest of this Afternoon...Isentropic lifting and upper-level
divergence ahead of the shortwave trough have generated scattered
light to moderate showers and isolated thunderstorms over western
Kentucky and Tennessee. This shallow activity is also revamped by a
narrow low-level jet around 50-55 knots located in the confluence of
the Mississippi and the Ohio where most of the lightning strikes
have been noted, per GLM. Therefore, there is high confidence that
rain chances will be on the rise from west to east this afternoon as
showers move to the area whereas low confidence exist for
thunderstorms this afternoon since the scant instability
accompanying the LLJ will stay west and south of the forecast area.
Otherwise, temperatures will remain fairly stable before sunset as
cloud coverage and thickness increase with small advection component
from the southeast winds.
Tonight...Heavier shower activity is expected between roughly 13/23Z
and 14/10Z when IVT is maximized across the area thanks in part to
the LLJ expanding and strengthening over central Kentucky, pumping
tropical moisture from the Gulf of Mexico, and increasing wind field
aloft, boosting DCVA and divergence. Rainfall totals are still
averaging 1-2 inches with narrow swaths of 2-3 inches in some of the
guidance, including the CMC, NAM, and ICON. Thus, there is high
confidence in precipitation accumulations; however, lower confidence
exist on the location of the maxima (2-3 inches) as deterministic
guidance varies between areas along the Ohio River and/or south-
central Kentucky. HREF 48-hour PMM depicts both maxima as potential
candidates to receive the aforementioned high-end amounts. Given
recent rainfalls, the area most susceptible to ponding and minor
flooding concerns will be the close to the Ohio River (north-central
Kentucky and southern Indiana). Flash Flood Guidance is generally
higher to the south. As for river flooding, HEFS guidance shows that
rivers can handle the incoming rain as it does not have any
significant probabilities of reaching minor flood stage in any major
basins. That being said, small creeks and low water passages might
quickly become overwhelmed during periods of heavy rain tonight.
Based on the lack of instability, timing of the frontal passage
(instability minimum), and strong near-surface inversion, chances of
organized severe weather are near zero. Last but not least,
lightning chances will be low and limited to strongest rain showers.
Tomorrow...Will continue mentioning mostly cloudy to cloudy sky
coverage given persistent saturation in the low-levels. Upper-level
low development and 250-mb jet transition across the region will
allow a longer residence time of the DCVA-related forcing and,
therefore, light rain chances will continue through the morning and
taper off from west to east in the afternoon as the cold front and
postfrontal dry air advection streams in from the west. Most of the
aforementioned shower activity will be light, expect for a period
late in the morning and early afternoon across the Bluegrass area
when brief, isolated showers and even a couple of thunder might
occur as the synoptic forcing lifts saturation to the mixed phase
and cold air aloft steepens the lapse rates, as shown in the GFS and
ECMWF forecast soundings. Temperature wise, cloudy skies, rain
chances, and breezy westerly winds favor a small temperature range
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 258 PM EST Wed Nov 13 2024
Thursday Night through Sunday Night...
We expect to be in the process of drying out Thursday night as the
upper trough axis shifts eastward and mid-level ridging builds into
the area. Low-level moisture will likely get trapped near the
surface resulting in low stratus and this will keep temps from
dropping too much, despite cool advection being in place. Lows will
range from the low-mid 40s in most locations.
For the period, Friday through Sunday night, mid-level ridging will
continue to build into the region resulting in dry conditions
through Sunday night. Temperatures at the beginning of the period
will be quite seasonal with highs on Friday mainly in the mid-upper
50s. Lows Friday night will drop into the upper 30s and lower 40s.
We'll see temps moderate a bit on Saturday with highs in the upper
50s to the lower 60s and overnight lows again in the upper 30s to
the lower 40s. Highs Sunday should be a bit warmer than Saturday
with readings in the mid-upper 60s and overnight lows in the mid-
upper 40s.
Monday through Wednesday...
Moving into next week, all eyes will be on a developing shortwave
trough axis coming through the four corners region into the southern
Plains. The trough axis may start off negatively tilted and then
move quickly through the central Plains and into the Midwest and
western Great Lakes. Moisture return ahead of this system remains
questionable across the Plains. However, strong wind fields and
strong synoptic scale ascent may lead to a swath of strong/severe
storms across the southern Plains into the Mid-MS Valley late Sunday
and into Monday. Some potential remains for strong/severe storms
ahead of the cold front coming into the western Ohio Valley by
Tuesday and into Wednesday. CSU ML guidance from 13/00Z run
highlight this potential in the GFS ensemble across the Ohio Valley.
However, I have concerns here that we may see the stronger jet
dynamics surge northward into the Great Lakes resulting in a
displacement of the shear away from better instability from the
lower OH Valley and points south. Nonetheless, will run with high
PoPs for Tue/Wed as this front pushes through.
Highs Monday look to warm into the mid-upper 60s with a few spots
along the KY/TN border getting close to 70. Lows Monday night will
be in the low-mid 50s. Highs Tuesday will again be in the upper 60s
to near 70. Wednesday's highs are a little uncertain given the
increasing spread in the placement of the front between the cooler
GFS and warmer Euro. For now, have gone with a blend here and will
go with highs in the mid-upper 50s.
Extended Forecast Discussion...
MUCH COLDER PATTERN SHAPING UP FOR LATE NEXT WEEK...
As we head into the extended forecast period, high latitude blocking
is forecast to increase over Greenland while a negative height
anomaly works eastward across the central US and eventually into the
eastern CONUS. Multi-model consensus forecasts a teleconnection
pattern featuring a -AO/-NAO/-EPO pattern with the PNA trending from
negative to positive. Confidence on this evolution of this pattern
is well above normal given the good model agreement both in the
deterministic as well as the ensembles. Uncertainty does rear its
head in how quickly this negative height anomaly will translate
east. The GFS and GEFS solutions that the colder pattern will get
here by Thursday, while the Euro and its EPS suggest it will be late
Friday/Saturday before it gets cold.
Internal signal analysis from early November has been quite
remarkable over the last couple of weeks. A strong signal passage
is current indicated around 11/22. This averages out well with the
faster GFS and slower Euro solutions. At the time of this passage,
a cold airmass will be in place to support wintry precipitation
across in the 11/21-11/23 time frame. Looking forward into week two
(week of Thanksgiving), colder than normal temperatures are likely
to continue, though there may be some attempts at moderation. Another
strong signal passage is centered around 11/26 and that could bring
another round of precipitation (likely wintry) to the area.
&&
.AVIATION /06Z TAFS THROUGH 12Z FRIDAY/...
Issued at 1241 AM EST Thu Nov 14 2024
Another wave of moderate rain showers will move across the region
over the next few hours, with rain becoming more scattered from west
to east after 09Z. In this band of rain showers, VIS should be
predominantly MVFR, though occasional dips to IFR would be possible
in the heaviest rain cores. While all sites except HNB currently
have VFR ceilings, MVFR/IFR CIGs to the west should overspread the
region later this morning, with the lowest ceilings expected just
ahead of the cold front passing through (14/09-16Z). As rain becomes
more showery/spotty later this morning, prevailing VIS should
improve, though occasional MVFR VIS in rain showers will be possible
through midday, especially at LEX/RGA. As the cold front passes,
winds will shift from S/SE to W. For this afternoon and into this
evening, MVFR ceilings and westerly winds are expected to continue.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
UPDATE...BTN
SHORT TERM...ALL
LONG TERM...MJ
AVIATION...CSG
Source:
LMK issues Area Forecast Discussion (AFD) at Nov 14, 12:42 AM EST ...Updated Aviation Discussion...---------------
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