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000
FXUS63 KLMK 140507
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
107 AM EDT Sun Apr 14 2024

.KEY MESSAGES...

*   Warm period ahead Sunday through Wednesday, with highs ranging
    from the upper 70s to lower 80s.

*   Stormy weather Tue night through Wednesday evening. Wednesday
    afternoon is the most concerning for strong to severe storms.

*   Significant cool-down appears increasingly likely next weekend.
    This may mean highs only in the 50s and lows falling into the
    upper 30s.

*   The Ohio River will run high this week but stay below flood
    stage at Louisville through at least mid-week. How much rain we
    get Tuesday night through Wednesday evening, and where the
    heaviest rain falls, will be a significant factor for river
    levels next weekend.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 308 PM EDT Sat Apr 13 2024

Mostly sunny skies and mild temperatures abound across central
Kentucky and southern Indiana this afternoon as a ridge of high
pressure extending from the Gulf of Mexico northward to Lake
Michigan is centered over the region. The pressure gradient between
this ridge of high pressure and two areas of low pressure over the
northern Great Plains and Quebec has led to a steady, but not overly
gusty west wind across much of the region so far today. As this
ridge axis moves east of the region later today, winds should back
to southwesterly before becoming light and southerly after sunset
tonight. Mostly clear skies should continue through the afternoon
and evening hours.

Tonight, a shortwave 850 mb trough will dive SE from central Canada
toward the northeastern U.S., as low-mid level ridging holds in
place across the Gulf of Mexico. This will lead to a strengthened
height gradient across the Ohio Valley, and the development of a 50-
55 kt WSW LLJ is anticipated across the region after midnight
tonight. While a strong inversion should be in place shortly after
sunset tonight, keeping the highest winds off the surface, a general
increase in SSW winds is expected late tonight into early tomorrow
morning. This LLJ will also bring warmer air with it, and lows
Sunday morning should be considerably milder than this morning.
Several hi-res models try to bring a few light rain showers across
the northern half of the CWA late tonight; however, this increase in
composite reflectivity appears to be associated with an increase in
mid-level (above 700 mb) moisture, with relatively dry air remaining
in the lower troposphere. As a result, will continue with the
previous forecast`s silent PoPs, though I wouldn`t be surprised if
one or two sprinkles occurs between midnight tonight and dawn Sunday.

For the day on Sunday, warm temperatures and breezy conditions
return to central KY and southern IN as SW winds increase ahead of
an approaching cold front, and stronger winds within the LLJ core
mix down to the surface with diurnal heating. Sustained winds of 15-
20 mph with gusts up to 30 mph are expected tomorrow morning into
the early afternoon, with winds relaxing a bit during the late
afternoon. Have nudged temperatures up slightly from NBM guidance,
as I think we could overperform given plenty of sunshine and
potential compressional heating ahead of the front. The cold front
will struggle to make it through the region tomorrow as the best
upper level forcing will shift off to the north and east. While
previous model guidance suggested isolated showers and thunderstorms
Sunday afternoon, latest hi-res sounding progs show a stout layer of
warm air aloft which provides enough CIN to suppress convective
activity this far south and west. Accordingly, we`ll keep a dry
forecast going through sunset tomorrow.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Issued at 308 PM EDT Sat Apr 13 2024

Unsettled weather for the first part of the new workweek, with
widespread showers and storms Tuesday night through Wednesday
evening. Still looking at the possibility of severe storms
Wednesday, primarily in the afternoon and early evening. Cooler
weather then moves in for the weekend.

The cold front approaching from our north on Sunday will lay out
east-west just north of the Ohio River Sunday night. We`ll be capped
here south of the front and the low level jet will weaken and move
off to the east. As a result will have a dry forecast and warm
temperatures with lows in the upper 50s to around 60.

Monday-Tuesday a northern stream jet streak will progress from the
Great Lakes to New England while a southern jetlet will advance from
the Four Corners to Texas and Oklahoma. A strengthening 500mb speed
max will advance to the Ozarks by Tuesday afternoon ahead of a deep
upper trough over the Rockies. At the surface a very broad
warm/moist sector ahead of this storm system on Monday will become a
more narrow corridor of heat and moisture on Tuesday as robust vapor
transport flows north form the western Gulf to the upper Mississippi
Valley. In southern Indiana and central Kentucky the stationary
surface front to our north Monday will lift northward Monday night
into Tuesday as strong low pressure moves across Nebraska. The best
chance of any storms will be in our north as a result, closer to the
surface boundary.

On Monday, heights will rise slightly in a capped warm sector with
weak shear. Deep RH will remain positioned off to our west. Not much
of a trigger other than the surface front, so the best chance of
rain may be isolated afternoon storms as convective temperatures are
surpassed. These storms would likely not be severe or long-lived.
Will keep PoPs low.

Tuesday we`ll be well in the warm sector. Storms that develop off to
our west Tuesday afternoon will head this way, and move through the
region Tuesday night. Though thunder and moderate to heavy rain can
be expected as the aforementioned corridor of increased moisture
moves through, storms should be undergoing a slow weakening trend
with weak lapse rates and decreasing instability overnight.

Wednesday: timing is everything. The question here is whether or not
early morning convection will move out quickly enough to allow the
atmosphere time to reload for afternoon development. Also, the
system overall should be on a weakening trend as the upper low lifts
into Canada and the surface reflection advances well to our north
from Wisconsin to Michigan. Nevertheless, as of right now the
general consensus on fropa timing is Wednesday evening, which may be
enough time for re-destabilization. Definitely something to watch
closely, because all severe modes will be possible with any renewed
convection. WPC does have the region in a marginal risk for
excessive rainfall as well. Winds outside thunderstorms will be
gusty on Wednesday ahead of the wrapped-up spring storm system.

A weak secondary system may bring scattered showers to the region
Thursday night, moving off to the east Friday. It`s behind this
system where the push of colder air will be as Canadian high
pressure drops from the Prairie Provinces to the mid-Missouri or Red
River Valley. The coldest night is likely to be Saturday night, with
lows in the upper 30s and lower 40s. There is a 20-30% chance of
temperatures cold enough to suggest frost, however, depending on
where the center of the high ends up, there may be a bit too much of
a breeze for much frost formation. Climatology says there`s still a
60% chance of Lexington seeing a temperature as cold as 36 degrees
at that point in the spring season, though a reading in the mid 30s
would still be about 10 degrees below normal.

&&

.AVIATION /06Z TAFS THROUGH 12Z MONDAY/...
Issued at 106 AM EDT Sun Apr 14 2024

VFR conditions expected through the forecast period. Strong winds
just above a surface inversion are resulting (or will result in here
shortly) LLWS issues for all TAF sites, and will continue a little
bit after sunrise until the lower boundary layer mixes out. Expect
gusts later this morning and afternoon to range from 20-25kts,
generally out of the southwest. Winds will subside some overnight as
the nocturnal inversion sets in, and while some very marginal LLWS
issues may develop again, they appear to be too weak to warrant
mention in TAF at this time.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.

&&

$$

SHORT TERM...CSG
LONG TERM...13
AVIATION...DM