Special Weather Statement, NWS Louisville, KY

Area Forecast Discussion
National Weather Service Louisville KY
911 AM EDT Fri Sep 21 2018

.Forecast Update...
Issued at 915 AM EDT Wed Sep 19 2018

A north-south line of isolated showers running from Jefferson County
KY to the Cumberland area is currently moving eastward. These
showers are not expected to grow, so expect just light rain in those
affected areas. Updated the forecast grids to account for this.
Afternoon forecast still looks good with mention of scattered
showers and storm chances so decided not to update Zone Forecast
Product.

&&

.Short Term...(Today and tonight)
Issued at 259 AM EDT Fri Sep 21 2018

This morning is looking to start off relatively quiet before things
get potentially busy this afternoon. A cold front currently in the
Midwest will race toward the lower Ohio Valley, but not make it into
our area until late this afternoon and evening. Several models
indicate storms could fire off by 18z along old outflow and
mesoscale boundaries well ahead of the cold front, though the timing
and placement of these storms remains difficult to forecast this far
out. There is higher confidence that we'll see a broken line of
storms develop near the cold front late this afternoon, impacting
southern Indiana and north-central Kentucky around or after 21z.

While deep layer shear isn't particularly strong, it's nothing to
dismiss either (0-6km bulk shear ~30kts). When you take into
consideration that storms will be firing off during peak heating,
there will be plenty of instability to work with ahead of the front
(MLCAPE between 1500-2500J/Kg). The combination of shear and
instability should be enough to support some strong to severe
storms, mostly in the form of multi-celluar clusters or broken
lines. For what it's worth, the 00z 3km NAM and HREF ensembles
indicate the potential for one or two embedded supercells within a
line, which isn't too unreasonable given that 30kts of deep layer
shear is borderline supportive of rotating updrafts. The main threat
with any strong/severe storm would be damaging winds, followed by
hail and heavy rainfall. PWATs are forecast to approach 2" ahead of
the cold front, and localized flooding issues may arise where storm
training occurs.

Models weaken the storms significantly between 00z-03z as
instability wanes after sunset. Winds will switch out of the north
behind the cold front, advecting in some refreshingly cooler, fall-
like air to start off the first day of autumn.

.Long Term...(Saturday through Thursday)
Issued at 255 AM EDT Fri Sep 21 2018

Active weather pattern will set up for the weekend and at least the
first half of next week. High confidence that several waves of
showers and storms will move through the area as a front becomes
hung up over the Ohio Valley, but confidence in the timing and
placement of the heaviest rainfall is substantially less. Highest
rainfall amounts over the coming week could push 4 inches, with the
greatest chance over south-central Kentucky. Even if it happens
steadily over the course of a week, that will likely result in rises
on some area rivers, and especially on some of the smaller creeks
and streams.

By Saturday morning the cold front will hang up somewhere near the
Kentucky/Tennessee border, with most of Kentucky in the shallow cool
and moist air trapped under a frontal inversion. Weak disturbances
will eject out of an upper trof over the southern Plains, producing
waves of mainly stratiform rain with no more than isolated embedded
thunder. Best rain chances will be across south-central Kentucky,
but another band could set up near the Ohio River, with some
potential for heavy rainfall due to a training setup. WPC Excessive
Rainfall outlook has a slight risk in Kentucky west of I-65, and
marginal elsewhere. Similar regime remains in place on Sunday,
perhaps with a bit more southward shift in the precip chances.

By Sunday night the flat upper flow backs SW, allowing the stalled
front to lift northward across the Ohio Valley. Broad southerly flow
on Monday could allow for decent coverage of precip area-wide. For
Monday night and Tuesday the focus for showers and storms shifts
north and west, mainly into southern Indiana as another front
approaches.

The next approaching front will push through Tue night/Wed, bringing
numerous showers and storms to the area. Could have a few strong
storms, and this pattern will bear watching for whether the tail end
of a squall line could again impact the Ohio Valley. For Wednesday
night and Thursday, we'll finally see lower humidity and a day
without rain throughout the Ohio Valley as the front pushes far
enough south and east to give way to a bubble of Canadian high
pressure.

&&

.Aviation...(12Z TAF Issuance)
Issued at 600 AM EDT Fri Sep 21 2018

A cold front will approach from the northwest late this afternoon
and evening. While there is excellent agreement amongst models that
a broken line of storms will develop along the cold front, there
will also be potential for storms to develop ahead of the cold front
early this afternoon. Confidence in the timing and placement of
these early afternoon storms continues to remains low, so VCTS has
been used at all TAF sites to account for storm potential.

Winds behind the cold front will quickly switch to the north, and
could be gusty at times. Models suggest some IFR/MVFR stratus
developing after midnight across parts of the KY Bluegrass and
southern KY, though confidence in the timing and northward extent of
this stratus is low. The BWG/LEX terminals would most likely be
impacted by the stratus at this time.

&&

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

Update...CG
Short Term...DM
Long Term...RAS
Aviation...DM

Hazardous Weather Outlook
National Weather Service Louisville KY
316 AM EDT Fri Sep 21 2018

INZ076>079-083-084-089>092-KYZ023>043-045>049-053>057-061>067-
070>078-081-082-220730-
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
316 AM EDT Fri Sep 21 2018 /216 AM CDT Fri Sep 21 2018/

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

.DAY ONE...Today and Tonight.

Scattered to numerous thunderstorms are expected this afternoon and
tonight ahead of a cold front. A few strong to severe storms will be
possible. The main threat in the strong to severe storms will be
damaging winds, followed by hail and heavy rainfall.

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

Waves of scattered to numerous thunderstorms Sunday night through
Wednesday will produce rainfall amounts of 2 to 4 inches with
isolated higher amounts. Localized flooding is possible where storms
move over the same locations. A few strong storms may produce gusty
winds Tuesday afternoon and Tuesday night.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be required late this afternoon into the
evening.

DM/RAS

Special Weather Statement
National Weather Service Louisville KY
121 PM EDT FRI SEP 21 2018

INZ077-084-089>092-KYZ024-025-211815-
Crawford-Washington-Floyd-Clark-Perry-Harrison-Meade-Breckinridge-
121 PM EDT FRI SEP 21 2018

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT NORTHWESTERN
HARRISON...NORTHWESTERN CLARK...EASTERN CRAWFORD...EASTERN PERRY...
NORTHWESTERN FLOYD...SOUTHEASTERN WASHINGTON...NORTHWESTERN MEADE AND
NORTH CENTRAL BRECKINRIDGE COUNTIES...

At 120 PM EDT/1220 PM CDT/, radar indicated strong thunderstorms were
located along a line extending from 7 miles south of Salem to near
Carefree Town to 12 miles northeast of Tell City. Movement was east
at 10 mph.

Winds in excess of 40 mph are possible with these storms.

Locations impacted include...
Carefree Town, New Providence Town, Mount Pleasant, Blue River, New
Pekin, Palmyra, Milltown, Borden, Leopold and Greenville.

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

LAT...LON 3855 8578 3791 8649 3805 8667 3855 8612
TIME...MOT...LOC 1720Z 270DEG 10KT 3850 8609 3827 8635 3807 8659

RJS