Special Weather Statement, NWS Louisville, KY

Area Forecast Discussion
National Weather Service Louisville KY
556 PM EDT Fri Aug 13 2021

.Mesoscale Update...
Issued at 556 PM EDT Fri Aug 13 2021

Thunderstorms have increased in coverage over the past hour in a
corridor of maximum moisture convergence stretching from middle
Tennessee to central Ohio as well as a local MLCAPE max around 2500
J/kg. The storms also are developing ahead and south of the
aforementioned MCV, which is now quickly approaching Cincinnati from
the west. DCAPEs are marginal (800-900 J/kg) and so far measured
wind gusts have mostly been in the 30-40 mph range. However, as of
this writing there is a particularly strong updraft in a
thunderstorm over Marion County that may result in stronger winds at
the surface as the cell collapses, and the Fayette County Mesonet
clocked a 44 mph gust with another cell. We are not out of the woods
yet with regard to gusty wind potential.

Having said that, most of the convection so far this afternoon has
struggled. Mid-level lapse rates are weak and shear is very weak,
especially over southern Kentucky but a little stronger over the
Bluegrass. The last couple of aircraft soundings out of SDF have
shown a warm layer at 900-850mb.

Given wet bulb zero heights around 12k' and lack of shear, severe
sized hail is unlikely. Smaller hail will still be possible in the
more robust storms, and has already been reported in Scott County KY.

Slow movement and training of storms has presented a local flood
potential as well.

Storms will continue to fire, with the greatest development and
coverage likely taking place over the next couple of hours or so.
The activity should slowly begin to wane this evening as we lose
insolation and the Cincinnati MCV moves off.

Additional showers and thunderstorm chances will continue tonight,
though, as the cold front to our north approaches.

Issued at 245 PM EDT Fri Aug 13 2021

...Strong to Severe Storms Remain Possible, Mainly East of I-65...

Very moist and moderately unstable air still sits over central
Kentucky, with a few lingering low-level boundaries from last
night's convection and a mid-level MCV pushing across southern
Indiana. The focus for storms thus far has been east of I-65, with
the current effective boundary roughly from Frankfort to
Campbellsville to Tompkinsville and moving slowly eastward.

Most of our storm development should continue to focus along and
east of this boundary, including through the Bluegrass region and
Lake Cumberland. The storms across the Bluegrass have the best
potential to become severe if mid-level winds increase enough ahead
of the MCV. Without this enhancement of deep-layer shear, a warm
layer near 400mb has thus far been able to keep storms from getting
tall enough to produce severe winds. Harrison County KY Mesonet has
reported wind gusts to 36 mph, so gusty winds are still in play and
it wouldn't take much improvement to open the door to severe winds.
So we will continue to highlight at least a localized damaging wind
threat.

For the I-65 corridor and west, mid-level clouds associated with the
MCV will put the brakes on development for at least a couple hours.
Still have opportunity for storms to fire later this afternoon into
this evening. Also worth watching is the cluster of storms in the
Missouri bootheel, as that could develop into another MCV that would
interact with our juicy air mass. However, it's not a wide window of
opportunity, and the best focus for storms seems to be over western
Tennessee. It's a lesser SVR threat west of I-65, but non-zero
especially in southern Kentucky. As you move north of the Western
Kentucky Parkway and into southern Indiana, the risk diminishes
greatly.

&&

.Short Term...(This evening through Saturday)
Issued at 245 PM EDT Fri Aug 13 2021

Once convection winds down around midnight tonight, what had
previously looked like a simple forecast of unusually pleasant mid-
August weather now seems more uncertain.

Cold front will take its sweet time pushing southward, leaving the
warm and muggy air mass in place overnight and at least into
Saturday morning. Will hang on to low POPs through the night, but
also keep QPF low as well.

For Saturday we will have to watch the southward progress of the
front, especially to see if any upstream MCVs will be able to
interact with it. POPs have been bumped up slightly, with 30-40%
chance south of the WK/BG Parkways and a 20% chance north of the
Parkways to the Ohio River. Afternoon showers and storms across
southern KY could be intense enough to drop some locally heavy
rainfall. Even with the muggy start, we should see dewpoints drop
through the day, especially across southern Indiana, so max temps in
the mid/upper 80s will actually feel like mid/upper 80s. South-
central Kentucky will not be as lucky, with dewpoints staying up
around 70 or a bit higher.

.Long Term...(Saturday night through Friday)
Issued at 255 PM EDT Fri Aug 13 2021

At the start of the period, expect to find general troughiness
moving into the MS Valley with areas of high pressure aloft centered
over the CA/NV border and the western Atlantic. The mid-level trough
is then expected to remain situated over the MS Valley through mid-
week before gradually lifting northeast towards the Great Lakes
region through the end of the week. At the surface, the cold front
initially located near the KY/TN border will continue to sink
southward, eventually stalling out over the TN Valley/Deep South,
before lifting back north as a warm front and washing out over the
area by midweek.

A quick return of southerly flow into the region as an inverted
surface trough sets up will help keep plenty of moisture over the
area as we move into next week, with PWATs remaining in the 1.7-2.0+
inch range. As pockets of energy ripple through the base of the
trough and over the area, there will be potential for precipitation
each day of the extended, keeping us in an unsettled pattern through
the end of the week. Will see a diurnal enhancement of precip
activity, with best chances of showers and storms occurring during
the afternoon and evening hours.

Temperatures throughout the period look to be near or just below
climatological normals. Highs will generally be in the lower to mid
80s, likely warming back into the upper 80s by next Friday.
Overnight lows will be in the mid to upper 60s with urban areas
possibly remaining in the lower 70s.

&&

.Aviation...(18Z TAF Issuance)
Issued at 115 PM EDT Fri Aug 13 2021

Main challenge is timing and impact of convection this afternoon and
evening. Plenty of Cu developing already, but a decent mid-level cig
keeping a lid on HNB and BWG for now. Expect to be just warm enough
by 19-20Z to pop off storms that will first affect SDF and LEX.
These two sites are also likely to see the most intense storms, so
included 30 kt wind gusts in the late afternoon/early evening TEMPO,
along with IFR vis and MVFR cigs. Could see the storms get into BWG
a bit later, but not expecting the same intensity there.  HNB could
see enough nearby action to warrant VCTS, but the probabilities are
too low to include any TS on the field in this TAF issuance.

Convection winds down in the 02-05Z time frame, with a modest push
of NE winds as the cold front passes. Could see some brief MVFR
ceilings on Sat morning in BWG and LEX, but that could be at least
partly conditional on getting some rain overnight, so confidence is
limited.

&&

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

Mesoscale...RAS/13
Short Term...RAS
Long Term...JML
Aviation...RAS

Hazardous Weather Outlook
National Weather Service Louisville KY
327 PM EDT Fri Aug 13 2021

INZ076>079-083-084-089>092-KYZ023>043-045>049-053>057-061>067-
070>078-081-082-141930-
Orange-Washington-Scott-Jefferson-Dubois-Crawford-Perry-Harrison-
Floyd-Clark-Hancock-Breckinridge-Meade-Ohio-Grayson-Hardin-Bullitt-
Oldham-Trimble-Henry-Shelby-Franklin-Spencer-Anderson-Woodford-
Fayette-Bourbon-Nicholas-Nelson-Mercer-Jessamine-Larue-Marion-Boyle-
Garrard-Madison-Butler-Edmonson-Hart-Green-Taylor-Casey-Lincoln-
Logan-Warren-Simpson-Allen-Barren-Monroe-Metcalfe-Adair-Russell-
Cumberland-Clinton-
Including the cities of Paoli, Salem, Scottsburg, Madison, Jasper,
English, Tell City, Corydon, New Albany, Jeffersonville, Lewisport,
Hawesville, Hardinsburg, Brandenburg, Hartford, Leitchfield,
Elizabethtown, Shepherdsville, Louisville, La Grange, Bedford,
Milton, New Castle, Shelbyville, Frankfort, Georgetown, Cynthiana,
Taylorsville, Lawrenceburg, Versailles, Lexington, Paris, Carlisle,
Bardstown, Springfield, Harrodsburg, Nicholasville, Winchester,
Hodgenville, Lebanon, Danville, Lancaster, Richmond, Morgantown,
Brownsville, Horse Cave, Greensburg, Campbellsville, Liberty,
Stanford, Russellville, Bowling Green, Franklin, Providence,
Scottsville, Glasgow, Tompkinsville, Edmonton, Columbia, Jamestown,
Burkesville, and Albany
327 PM EDT Fri Aug 13 2021 /227 PM CDT Fri Aug 13 2021/

This hazardous weather outlook is for portions of south central
Indiana and Central Kentucky.

.DAY ONE...Tonight.

Thunderstorms through this evening could become strong to severe,
with locally damaging wind gusts possible. Torrential rainfall and
frequent lightning will be secondary threats.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

Scattered afternoon and evening thunderstorms are expected Saturday
and Sunday over south central Kentucky, and expanding across the
entire outlook area Monday through Thursday. The stronger storms
could produce locally heavy rainfall.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be required this afternoon and evening.

RAS/JML

Special Weather Statement
National Weather Service Louisville KY
611 PM EDT Fri Aug 13 2021

KYZ040-047-048-056-132245-
Mercer KY-Woodford KY-Jessamine KY-Garrard KY-
611 PM EDT Fri Aug 13 2021

...A strong thunderstorm will impact portions of northeastern Mercer,
southeastern Woodford, northwestern Garrard and western Jessamine
Counties through 645 PM EDT...

At 611 PM EDT, Doppler radar was tracking a strong thunderstorm 8
miles northeast of Harrodsburg, moving east at 15 mph.

HAZARD...Winds in excess of 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
  Nicholasville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3777 8480 3788 8485 3800 8463 3799 8463
      3781 8455
TIME...MOT...LOC 2211Z 250DEG 11KT 3786 8474

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

EBW

Special Weather Statement
National Weather Service Louisville KY
613 PM EDT Fri Aug 13 2021

KYZ045-132245-
Nelson KY-
613 PM EDT Fri Aug 13 2021

...A strong thunderstorm will impact portions of central Nelson
County through 645 PM EDT...

At 612 PM EDT, Doppler radar was tracking a strong thunderstorm near
Bardstown, moving northeast at 10 mph.

HAZARD...Winds in excess of 40 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
  Bardstown.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3774 8557 3780 8561 3790 8548 3779 8540
TIME...MOT...LOC 2212Z 241DEG 8KT 3779 8555

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

EBW

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Special Weather Statement
National Weather Service Louisville KY
627 PM EDT Fri Aug 13 2021

KYZ042-043-132300-
Bourbon KY-Nicholas KY-
627 PM EDT Fri Aug 13 2021

...A strong thunderstorm will impact portions of northeastern Bourbon
and central Nicholas Counties through 700 PM EDT...

At 626 PM EDT, Doppler radar was tracking a strong thunderstorm near
Carlisle, moving northeast at 15 mph.

HAZARD...Winds in excess of 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
  Carlisle.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3822 8395 3814 8413 3828 8423 3842 8405
      3827 8389
TIME...MOT...LOC 2226Z 237DEG 13KT 3826 8412

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

EBW

Special Weather Statement
National Weather Service Louisville KY
633 PM EDT Fri Aug 13 2021

KYZ039-047-132300-
Mercer KY-Anderson KY-
633 PM EDT Fri Aug 13 2021

...A strong thunderstorm will impact portions of northwestern Mercer
and Anderson Counties through 700 PM EDT...

At 633 PM EDT, Doppler radar was tracking a strong thunderstorm 8
miles southwest of Lawrenceburg, moving northeast at 10 mph.

HAZARD...Winds in excess of 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
  Lawrenceburg.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

To report severe weather, contact your nearest law enforcement
agency. They will relay your report to the National Weather Service
office in Louisville.

&&

LAT...LON 3795 8482 3789 8506 3799 8515 3800 8515
      3800 8513 3801 8512 3802 8513 3804 8510
      3804 8508 3805 8507 3812 8497 3805 8487
TIME...MOT...LOC 2233Z 240DEG 9KT 3797 8502

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

EBW

Special Weather Statement
National Weather Service Louisville KY
636 PM EDT Fri Aug 13 2021

KYZ029-045-132300-
Bullitt KY-Nelson KY-
636 PM EDT Fri Aug 13 2021

...A strong thunderstorm will impact portions of northwestern Nelson
and southeastern Bullitt Counties through 700 PM EDT...

At 636 PM EDT, Doppler radar was tracking a strong thunderstorm 8
miles southeast of Shepherdsville, moving east at 10 mph.

HAZARD...Winds in excess of 40 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

This storm will remain over mainly rural areas of southeastern
Bullitt and northwestern Nelson Counties, including the following
locations... Samuels, Ridgetop, Solitude, Hobbs, Scuffletown,
Deatsville, Bourbon Springs, Brownington, Lotus and Coxs Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

To report severe weather, contact your nearest law enforcement
agency. They will relay your report to the National Weather Service
office in Louisville.

&&

LAT...LON 3783 8566 3790 8569 3799 8551 3785 8545
TIME...MOT...LOC 2236Z 253DEG 8KT 3788 8563

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

EBW