LMK issues Area Forecast Discussion (AFD) at Mar 30, 1:55 AM EDT ...Updated Aviation Discussion...685
FXUS63 KLMK 300555
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
155 AM EDT Sun Mar 30 2025
...Updated Aviation Discussion...
.KEY MESSAGES...
* Strong to severe storms anticipated Sunday night, which will be
capable of all severe hazards (wind, hail, tornado, locally heavy
downpours). Some of these hazards may bring significant damage.
* Another strong low pressure system is expected to bring windy
conditions to the region Wednesday, and thunderstorms, possibly
severe, Wednesday evening into Wednesday night.
* Additional showers and storms are expected to continue from
Thursday into the weekend, leading to significant rainfall totals
and potential flooding by late in the week thorugh the weekend and
possibly into the early part of the following week.
&&
.UPDATE...
Issued at 1002 PM EDT Sat Mar 29 2025
Overall the previous forecast is pretty well on track. We have seen
one weakening band of showers pretty much fizzle out as it got near
the I-65 corridor. Next band extends from near Kentucky Lake to just
north of Huntsville, AL, and will lift NNE overnight. Expect it to
hold up better than the last band of precip as dewpoints have risen
into the 50s, but overall coverage will still be scattered. Still
confident in keeping overnight POPs around 50-60 percent with light
QPF, so no changes are planned other than tweaks to the hourly
grids, especially POPs.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 311 PM EDT Sat Mar 29 2025
Currently - Sunday Morning...
The southern stream wave that originated over Texas is just
southwest of the region currently. As it continues to move
northeast, it will weaken as ridging over the Ohio Valley and
Midwest amplifies. The 40-45kt LLJ is working east over the region
this afternoon, which has lead to some light showers moving in from
the west. Ample mixing has allowed for wind gusts up to 35mph. These
conditions will continue through the overnight period. As the
shortwave moves over the region tonight, and coupled with good
moisture transport along the LLJ, showers will increase in coverage.
Light to moderate showers will move through tonight along the LLJ
and exit the Bluegrass by mid morning. This evening, the low levels
will see a pronounced dry layer that will saturate through the
night, and as this occurs we could mix down some gusty winds up to
35mph. Thunder chances are low, but wouldn't rule out some isolated
thunder in the morning. Due to showers and breezy conditions, low
temperatures will be unseasonably warm in the upper 50s and low 60s,
with urban areas in the mid 60s.
Sunday Afternoon - Sunday Night...
**Severe Storms Capable of Producing Strong Tornadoes, Strong Wind,
and Large Hail Will Move Through Sunday Night**
Troughing currently located over the Rockies will move northeast and
develop a low pressure system over the central Plains. The trough
and associated low pressure center will strengthen as it moves into
the Ohio Valley Sunday evening. Initially negatively tilted, the
trough will become more neutrally tilted overnight as it progresses
northeast. A developing upper and mid level jet will place the
southern Ohio Valley under the right entrance region, providing
additional lift. A 40-45kt LLJ will move over southern Indiana and
northern Kentucky in the late afternoon.
Continued southerly flow and warm air advection will keep
temperatures warm. In the afternoon, the LLJ will help to increase
moisture transport and raise dew points into the low to mid 60s.
This moisture profile will bring PWATs into the 1.3-1.5 inch range,
which is above the 90th percentile climatology for this time of
year.
Looking into the thermal profile, there is a cap present for most of
the afternoon, which will help to limit convective activity through
most of the day. Additional the shear profile is weak through the
day, which will not help to organize storms. Shear and instability
will increase in the late afternoon and evening. Surface based
instability is forecasted to peak between 1250-1800J/kg ahead of the
line of storms, with some solutions suggesting a short-lived
2000+J/kg. Deep layer shear is expected to be strong, 40-50kts,
with ample curvature in the low levels.
Given these favorable ingredients, a strong QLCS is anticipated to
move through the region bringing damaging winds, large hail, and
potentially multiple tornadoes, some of which could be long-track
tornadoes. Segments of this QLCS could bow, leading to a potentially
significant wind threat. This QLCS will be the main show for the
night, however, there is a chance for discrete cells out ahead of
the line. These cells may start start out in the late afternoon as
disorganized cells and then become more organized as shear
increases, later growing upscale into the QLCS line. Highest chance
(although low confidence) would be west of I-65 and west of I-71.
These cells would likely produce the largest hail threat.
Timing: 21Z and beyond, the threat for discrete cells increases. The
line will likely approach the region from the northwest between 0-2Z
and exit to the southeast between 8-10Z. As the line approaches your
location, you may experience severe conditions for up to 2 hours.
Confidence: confidence has definitely increased over the last
several days and model guidance has converged for timing and
strength of the line. The discrete cells ahead of the line still
remain with low confidence.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 311 PM EDT Sat Mar 29 2025
A weak wave moving up Sunday night's cold front from middle
Tennessee to eastern Kentucky will prolong shower chances into
Monday, gradually ending from west to east over the course of the
day. Dry weather will then prevail Monday night through at least
Tuesday night as a long north-south ridge of high pressure slides
from the Plains to the East Coast. This will be the time period for
recovering from the Sunday night storms and preparing for Wednesday
night storms. Highs will generally range from the mid 50s to mid 60s
Monday and Tuesday, with lows in the lower and middle 30s early
Tuesday morning.
Attention then turns to the potentially volatile weather for
Wednesday-Thursday, especially Wednesday night. Core of a 250mb
Pacific jet speed max and 500mb vort max will push northeastward
from the Midwest to the Great Lakes ahead of a vertically deep
trough over the Upper Plains/Mississippi Valley. An anomalously deep
surface low will travel a similar route from NE/IA to Upper
Michigan/Lake Superior, weakening slightly as it heads towards
Canada. The middle Ohio and Tennessee Valleys will be well within
the warm sector of this system. Very strong surface-700mb winds will
likely produce advisory-level surface wind gusts on Wednesday and
will also bring copious amounts of moisture northward from the
western Gulf, resulting in GFS/EC model agreement of daily record
precipitable water values over 1.50" by Wednesday night.
Unsurprisingly, shear will very strong.
As of right now, supercells are progged to develop in a corridor of
enhanced surface-based instability just ahead of the aforementioned
synoptic features, possibly initially over Illinois and Missouri and
then growing into a line from as far northeast as Michigan to as far
southwest as the Arklatex as the system pushes east. The line of
storms, either a QLCS or line of supercells, would then cross
southern Indiana and central Kentucky Wednesday night with all
severe hazards in play. Though instability will wane overnight,
operational GFS and ensemble LREF hodographs are impressive and
suggest the possibility of nighttime tornadoes, possibly significant
ones, especially west of Interstate 65. The abundant atmospheric
moisture and very deep warm cloud depths will facilitate torrential
downpours, with flash flooding a possibility especially late
Wednesday night into Thursday morning.
There has been some recent consistency in the model data that the
front that generates Wednesday's storms may greatly slow its forward
progression or possibly oscillate back-and-forth across the area as
waves move up it late this week and into the weekend. High pressure
centered off the southeast U.S. coast will pump a steady stream of
moisture northward that will interact with the baroclinic zone to
support periods of showers and thunderstorms. Heavy rains will be
possible as anomalously high PWATs remain in place. EC EFI showing a
very good signal for unusual QPF amounts in the Ohio Valley Thursday-
Friday. WPC Day 1-7 QPF (so, that would include Sunday night's
storms, Wednesday night's storms, and Thursday-weekend showers and
storms) is showing a total of 6-9" of rain along and a few counties
either side of the Ohio River, with 4-6" in southern Kentucky over
the course of the week. This is in good agreement with LREF ensemble
7-day mean QPF. Though green-up has begun, it is only in the early
stages so most of the rain will go into the soil and streams rather
than getting taken up by plants. In addition to localized flash
flooding, OHRFC has indicated a 30% chance of at least minor to
moderate river flooding on most southern Indiana and central
Kentucky rivers by late this coming week into the early part of the
following week.
Of course, all of the above is just a forecast based on the latest
data. Small shifts in the storm track can result in large changes in
the forecast at any one point. Stay tuned to forecast updates over
the coming days.
&&
.AVIATION /06Z TAFS THROUGH 12Z MONDAY/...
Issued at 155 AM EDT Sun Mar 30 2025
A band of light to moderate SHRA will continue to lift NE across
central KY and southern IN early this morning, with ceilings
lowering to MVFR at HNB/SDF/BWG over the next six hours or so.
LEX/RGA should remain VFR through the morning, with some improvement
across the board this afternoon.
Behind the early morning wave of showers (after 12Z Sun), more
isolated to scattered showers will be possible through much of the
daytime. Any meaningful TSRA threat should hold off until after 21Z
Sun.
Scattered to numerous TSRA are forecast 21Z Sun to 06Z Mon. A few
isolated TSRA will be possible in the early evening hours, but the
main TSRA impact will be from a line of storms that crosses the
region ahead of a strong cold front. Expect brief IFR or lower
conditions with heavy TSRA.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
UPDATE...RAS
SHORT TERM...SRW
LONG TERM...13
AVIATION...EBW
Source:
LMK issues Area Forecast Discussion (AFD) at Mar 30, 1:55 AM EDT ...Updated Aviation Discussion...---------------
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