Special Weather Statement, NWS Louisville, KY

Area Forecast Discussion
National Weather Service Louisville KY
816 AM EDT WED JUN 22 2016

...Forecast Update...
Issued at 815 AM EDT Wed Jun 22 2016

Large scale MCS continues to grow upscale across portions of
southern Indiana and north-central Kentucky this morning.  Storms
are growing upscale to the south and southeast and this activity
will primarily affect our southeastern Indiana counties and much of
our far north-central and Bluegrass counties later this morning.
Best chances of rain will be north of a line from Salem Indiana, to
just north of the Louisville metro area, eastward to near the
Lexington area...with areas along and north of I-64 in KY getting
most of the action.

In terms of sensible weather, torrential rainfall, gusty winds, and
very frequent cloud to ground lightning will be possible with this
activity as it pushes eastward.  A quick 1-2 inches of rainfall will
also be possible as this activity drops south and east.

Have made some major adjustments in the forecast grids to increase
PoPs substantially across our northeastern third of our CWA (SE IN
and into the Bluegrass region). Also upped QPF amounts with general
basin averages of 1-1.25 inches...though locally as much as 2 inches
could fall in some areas.  We expect this first wave of MCS activity
to push east of our area later this morning.  Upstream activity near
Peoria and Springfield, IL may clip our northern areas again later
this morning, but the actual warm frontal boundary should begin to
lift northward at the same time which may result in later activity
passing a little more to the north.

No real changes for the afternoon period of weather as of this
update.  Will continue to evaluate that time period later this
morning.

.SHORT TERM (Now through Thursday)...
Issued at 301 AM EDT Wed Jun 22 2016

The best chance for the most widespread thunderstorm activity today
will be this morning as an MCS getting itself together over
southeast Iowa and central Illinois during the pre-dawn hours moves
and propagates to the southeast into southern Indiana and northern
Kentucky during the mid and late morning hours. Models are progging
30-40kt of 0-6km bulk shear this morning, but it will be a
climatologically unfavorable time of day for severe weather. SPC
SREF supports this idea with diminishing severe thunderstorm probs
as the convection enters the region.

Once the morning convection tapers off and/or proceeds to the east
out of the area, the region will become very unstable this
afternoon. However, it is difficult to find a synoptic scale trigger
for storms as we sit in the warm sector ahead of low pressure over
Iowa and a warm front reaching southeastward into the upper Ohio
Valley. Thunderstorm development this afternoon will be concentrated
across northern Illinois ahead of the surface low, a 5H speed max
and 850 jet, and behind the entrance region of an upper jet streak.
Down here in southern Indiana and central Kentucky we will need to
watch out for low level boundaries left over from the morning
convection and differential heating boundaries from the morning
clouds. Further hampering storm development here this afternoon will
be a cap that is expected for form around 700hPa. However, lapse
rates above the inversion are expected to be very steep, so if
something can break through the cap, it could become strong quickly.
Wet bulb zero heights will be rather high, and DCAPE isn't progged
to be all that impressive, but gusty winds and small hail would
still be possible if any storms can get going. The best chance for
storms will probably be from southern Indiana to the northern Blue
Grass closest to the surface warm front and in zone of best deep
layer shear.

High temperatures today will be largely dependent on morning rain
and clouds. Will go coolest in the Blue Grass with highs in the mid-
upper 80s, and warmer southwest with lower 90s in the western coal
fields and Pennyrile.

The storms that erupt over northern Illinois this afternoon will
quickly organize into an MCS, possibly a derecho, and tear ESE
across northern Indiana and into Ohio tonight. This system should
stay just north of the LMK CWA, though we can't rule out some cells
from southeast Indiana into the northern Blue Grass. It will be a
rather uncomfortable night with muggy lows in the middle and upper
70s.

Thursday the Iowa low will be moving into the central Appalachians
and dragging its trailing cold front (or perhaps outflow boundary
from tonight's MCS) into southern Indiana and central Kentucky. We
will once again become extremely unstable by afternoon (SWEAT Index
peaking around 500, steep mid level lapse rates), this time with a
coherent trigger. Moisture will pool along the front, with good
model agreement of precipitable water values above 2 inches. Capping
will be weaker than today and a more pronounced dry layer aloft will
result in stronger DCAPE than what we see today, in the 1100-1400
J/kg neighborhood. Wet bulb zero heights may come down a bit,
especially over the Blue Grass. So, storms are expected to fire in
the afternoon in conjunction with the surface boundary and we will
probably see some severe weather. Highs will be around 90, but
oppressive dew points in the lower and middle 70s will take heat
index readings into the 100-105 degree range in the afternoon.

.LONG TERM (Thursday night through Tuesday)...
Issued at 212 AM EDT Wed Jun 22 2016

Storms will gradually sag south and taper off Thursday night as the
cold front drops down across the region. By Friday all areas should
be dry, with the possible exception of an afternoon thunderstorm
right along the Tennessee border near the old front.

Upper ridging will move in for the weekend, providing us with mostly
dry conditions and very warm temperatures. Can't rule out some
afternoon convection on Sunday as we get into a moist return flow,
but most places should remain dry under the upper ridge. High
temperatures will be in the low to mid 90s.

The ridge will get suppressed Mon-Tue by an upper trof riding along
the U.S./Canada border. A cold front will drop southward through the
region Monday and Monday night, accompanied by scattered
thunderstorms. The fate of the front on Tuesday is in question, but
for now will lean toward the ECMWF solution which depicts a slower,
more typical for summertime, movement and a continuing possibility
of convection on Tuesday.

&&

.AVIATION (12Z TAF Update)...
Issued at 645 AM EDT Wed Jun 22 2016

Convection along the warm front over Illinois has been slow to
expand SE overnight, but finally gaining some confidence in the hi-
res models in the last hour as the boundary is starting to light up
between HUF and BMG. Expect convection to start impacting SDF and
LEX between 13-15Z, and last until early afternoon. Will carry
prevailing SHRA with VCTS/CB mention, but expect ceilings to stay
mainly VFR. Forecast of prevailing MVFR vis may be a bit pessimistic
by the book definition, but seems prudent given that at some point a
brief IFR episode is likely.

Precip should shut off early-mid afternoon as the warm front lifts
to the north. BWG and SDF will end up well under a mid-level cap,
but LEX will have a few hrs of VCTS in the very late afternoon and
evening, given both the possibility of a late-day pop-up, or a
glancing blow from the convective complex that's expected to pass to
the north. Not enough confidence to try to pin down impacts from
that wave, so VCTS/CB mentions will do it for now, but brief
restrictions to vis will again be possible.

Solid warm sector sets up overnight, so SW winds will actually
increase through the night to around 12-15 kt. Planning period at
SDF will see further veering to WSW, and gusts 20-25 kt.

&&

.LMK Watches/Warnings/Advisories...
KY...NONE.
IN...NONE.
&&

Update.........MJ
Short Term.....13
Long Term......13
Aviation.......RAS

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LOUISVILLE KY
738 AM EDT WED JUN 22 2016

INZ076-077-221215-
WASHINGTON-ORANGE-
738 AM EDT WED JUN 22 2016

...A CLUSTER OF STRONG THUNDERSTORMS WILL AFFECT EASTERN ORANGE AND
WASHINGTON COUNTIES...

AT 738 AM EDT...A CLUSTER OF STRONG THUNDERSTORMS WAS ALONG A LINE
EXTENDING FROM 10 MILES SOUTHEAST OF BEDFORD TO 11 MILES NORTHEAST OF
ENGLISH...AND MOVING EAST AT 35 MPH.

WINDS IN EXCESS OF 30 MPH AND PEA SIZE HAIL ARE POSSIBLE WITH THESE
STORMS.

LOCATIONS IMPACTED INCLUDE...
SALEM...BLUE RIVER...NEW PEKIN...STAMPERS CREEK...CAMPBELLSBURG...
HARDINSBURG...LITTLE YORK...LIVONIA...SALTILLO AND FREDERICKSBURG.

TORRENTIAL RAINFALL IS ALSO OCCURRING WITH THESE STORMS...AND MAY
CAUSE LOCALIZED FLOODING. DO NOT DRIVE YOUR VEHICLE THROUGH FLOODED
ROADWAYS.

FREQUENT CLOUD TO GROUND LIGHTNING IS OCCURRING WITH THIS STORM.
LIGHTNING CAN STRIKE 15 MILES AWAY FROM A THUNDERSTORM. SEEK A SAFE
SHELTER INSIDE A BUILDING OR VEHICLE.

LAT...LON 3876 8603 3877 8599 3875 8598 3876 8594
      3875 8590 3858 8588 3857 8586 3852 8587
      3849 8599 3842 8600 3842 8631 3840 8631
      3840 8638 3869 8642 3869 8631 3873 8631
      3876 8628 3878 8620 3876 8614 3878 8609
TIME...MOT...LOC 1138Z 256DEG 29KT 3876 8634 3845 8630

ZT

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LOUISVILLE KY
809 AM EDT WED JUN 22 2016

INZ077-078-090>092-KYZ030-031-221245-
WASHINGTON-SCOTT-FLOYD-CLARK-HARRISON-JEFFERSON-OLDHAM-
809 AM EDT WED JUN 22 2016

...A CLUSTER OF STRONG THUNDERSTORMS WILL AFFECT NORTHEASTERN
HARRISON...SOUTHWESTERN SCOTT...FLOYD...WASHINGTON...CLARK...
JEFFERSON AND OLDHAM COUNTIES...

AT 809 AM EDT...A CLUSTER OF STRONG THUNDERSTORMS WAS ALONG A LINE
EXTENDING FROM 8 MILES EAST OF SALEM TO 8 MILES SOUTHWEST OF NEW
PROVIDENCE TOWN...AND MOVING SOUTHEAST AT 35 MPH.

WINDS 30 TO 40 MPH ARE POSSIBLE WITH THESE STORMS. EXPECT TORRENTIAL
RAINFALL AND LOCALIZED FLOODING IS POSSIBLE IN URBAN AREAS.

LOCATIONS IMPACTED INCLUDE...
LOUISVILLE...JEFFERSONVILLE...NEW ALBANY...JEFFERSONTOWN...ST. MATTHEWS...
LYNDON...LA GRANGE...MIDDLETOWN...SALEM AND DOUGLASS HILLS.

TORRENTIAL RAINFALL IS ALSO OCCURRING WITH THESE STORMS...AND MAY
CAUSE LOCALIZED FLOODING. DO NOT DRIVE YOUR VEHICLE THROUGH FLOODED
ROADWAYS.

FREQUENT CLOUD TO GROUND LIGHTNING IS OCCURRING WITH THIS STORM.
LIGHTNING CAN STRIKE 15 MILES AWAY FROM A THUNDERSTORM. SEEK A SAFE
SHELTER INSIDE A BUILDING OR VEHICLE.

LAT...LON 3849 8533 3830 8544 3829 8546 3828 8545
      3813 8553 3839 8626 3841 8625 3842 8627
      3875 8611
TIME...MOT...LOC 1209Z 296DEG 31KT 3861 8595 3837 8603

ZT

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