Special Weather Statement, NWS Louisville, KY

Area Forecast Discussion
National Weather Service Louisville KY
1017 PM EDT Wed Jul 20 2022

.Mesoscale Update...
Issued at 1017 PM EDT Wed Jul 20 2022

Convection has strengthen a bit more over the last hour across
portions of south-central KY.  Two cluster of storms are being
monitored across south-central KY.  The first is across portions of
Marion, Taylor, Boyle and northern Casey counties.  Convection is
within an instability maximum with MLCAPE values in the 3500-4000
J/kg range.  While instability is quite robust, vertical wind shear
remains generally weak in this area.  However, we'll be on guard for
this convection to take on more bowing like structures as they
become more outflow dominated.  Additionally, a localized flood
threat is possible in this corridor as well as storms are training
from west-east.  A Flood Advisory has been posted, but a warning may
be required if continued training occurs.  Further south across
Monroe and Cumberland counties, a cluster of strong storms with
heavy rainfall and lightning will continue to push eastward.

Some additional convection has continued to persist out across the
Pennyrile region of western KY.  This activity will push off to the
east-southeast over the next few hours producing some gusty winds,
intense lightning, and heavy rainfall.

Issued at 907 PM EDT Wed Jul 20 2022

Convection that developed over southwestern IN struggled as it moved
east toward our CWA.  It appears that very marginal mid-level lapse
rates prevented these storms from gaining too much strength.  This
convection has diminished in coverage with only a remnant
shower/storm that will move through southern Perry, IN and northern
Breckinridge counties.  Some additional convection has developed
over southern IN which will affect portions of Clark IN and perhaps
portions of Oldham county over the next hour.

Second batch of convection has developed along an instability axis
from Bowling Green northeast through the Lexington Metro area. This
convection is currently sub-severe.  The latest models suggest that
convection may grow more upscale over the next 1-2 hours across our
southeast sections.  Overall severe threat looks to be low here due
to the lack of vertical wind shear, though instability remains quite
high across the region.  With this convection, we expect wind gusts
of 40-45 mph and possibly some marble to dime sized hail with the
strongest cores that go up.

Lastly, will also do a quick update to the zones to drop the Heat
Advisory and Excessive Heat Headlines that expired at 900 PM EDT.

Issued at 655 PM EDT Wed Jul 20 2022

After a bit of delay due to some capping near 850 hPa, convection
has developed ahead of the approaching cold front along a pre-
frontal confluence.  Activity is developing within a very unstable
atmosphere where MLCAPE values are in the 3500-4500 J/kg range.
Objective analysis has around 25-30kts of shear, though regional
VWP's suggest more of 30-35kts which is sufficient for organized
convection.

Based on environmental parameters and high resolution guidance,
convection looks to remain generally multi-cellular in nature with a
threat of storms becoming more outflow dominant with time.  So a
transition from multi-cellular to bowing segments is likely.  Main
uncertainty here remains overall coverage.  As of this writing, the
highest risk of strong/severe weather will remain west of the I-65
corridor for the next 1-2 hours.  Should overall coverage increase,
and there is some evidence of that already, a SVR box could be
issued for portions of the LMK CWA over the next hour.

&&

.Short Term...(This evening through Thursday)
Issued at 323 PM EDT Wed Jul 20 2022

As a low pressure system in the middle of the Great Lakes continues
its eastern trek, its trailing cold front approaches the Lower Ohio
Valley this evening. This is expected to generate a line of showers
and storms. At first a few cells are expected to fire across
southern Indiana around 23z. The line will continue to the southeast
as it fills in and becomes a mostly solid line of convection across
the rest of central Kentucky. Severe weather chances will come to an
end around 01z. Earlier concerns of low level rotation with the
system have dissipated as low level SRH remain marginal. Plenty of
instability remains with MLCAPE values around 3,500 J/kg. Low level
lapse rates are steep with DCAPE values in the 1,500 J/kg range, so
gusty winds are the the main threat. However,some of the latest CAMs
have increased a low level inversion just off the surface. If this
materializes, this will lower the wind threat. Mid-level lapse rates
are unimpressive, limiting any hail to the lower end.

Our Lake Cumberland region is under a Slight risk for Excessive
Rainfall this evening due to expected heavy rainfall rates.
Widespread flooding isn't expected, but dew to 1-2" per hour rates
and some of the lower Flash Flood Guidance (1.5-1.75 in an hour)in
the area the Slight was placed over the area.

Dew points have been overachieving in our southwestern counties,
resulting in heat indices nearing Excessive Heat Warning levels, so
a warning will be forthcoming for the affected area.

Tomorrow, behind the front, temperatures will be limited to the
upper 80s to low 90s, and dew points will remain in the 60s for most
with a few 70s possible in southern Kentucky. Skies will be clear
and sunny.

.Long Term...(Thursday night through Wednesday)
Issued at 330 PM EDT Wed Jul 20 2022

Synopsis...The first half of the medium range 500-mb pattern will
feature an eastward- expanding ridge, which along with the quasi
stationary Southwest dome of high pressure, will allow positive
height anomalies to pervade from the Great Basin to the central
Plains and the Southeast. On the other hand, deep closed low over
Canada will maintain below-normal height anomalies on the northern
third of the CONUS as low-amplitude shortwave troughs travel from
the Pacific Northwest through the northern Plains to later round the
base of the low in the Great Lakes vicinity. The above scenario will
account for a mostly zonal upper jet oriented across the northern
Plains into the Great Lakes and a vorticity maxima/frontal waves
corridor positioned roughly on the upper Ohio Valley.

Model Predictability...Overall, there is good model agreement on the
large scale pattern throughout the weekend with subtle differences
appearing by next week regarding the intensity and location of the
Canadian closed low, per WPC cluster phase diagram, which will be
considered typical given the lead time. On the mesoscale level, the
Canadian 20/00Z run had low rain chances for the Friday night-
Saturday morning period in southern Indiana and northern Kentucky
versus a dry forecast from the GFS and ECMWF. However, the new
20/12Z run has pushed the rain farther north and clear the area.
Moreover, area-wide Sunday high temperatures populated on the high
end as they compare to the 90th percentile of the forecast MaxT
distribution and slightly above the 75th percentile of the NBM. It
is important to mention that the 20/12Z ECWMF came as the upper
extreme outlier. Therefore, decided to go with the new WPC guidance
for this parameter.

Friday...Weakening cold front will transit trough the area, but no
weather will be associated with it, aside from a NW wind shift and
upper-level clouds, as dry air remains anchored in the mid to low
levels with a shallow inversion later around 950 mb. Highs will stay
well above-normal (low to mid 90s) with dewpoints dropping below 70
after the weak frontal passage, so the heat index will not make it
to the triple digits.

Saturday - Sunday...The previously-mentioned weak cold front will
stall roughly along southern Kentucky/northern Tennessee and then
lifting back up to the upper Ohio Valley during Saturday. This will
allow a higher theta-e airmass to advance northward and eventually
host possible heat advisory headlines both on Saturday and Sunday.
So far, hotter temperatures are expected on Saturday as southerly
wind WAA and solar heating will be maximized under mostly sunny
conditions. The adjustments made to Sunday high temps (see section
above) and the intrusion of high clouds from the west-northwest will
probably limit heating in the afternoon, but there is still
possibility to achieve heat indexes above 100 degrees.

Next Week...A baroclinic frontal boundary will be oscillating
at/near the lower Ohio Valley which will ram up the rain and storm
chances. There is indication that several vort maxes will be riding
this boundary, so the possibility of a low-end severe weather risk
cannot be ruled out, either. Meanwhile, forecast highs range from
the upper 80s in southern Indiana to the low 90s in far south-
central Kentucky as the CWA sits in the warm sector with dewpoints
into the low 70s. However, this might vary as convection potentially
develops following the diurnal cycle.

&&

.Aviation...(00Z TAF Issuance)
Issued at 700 PM EDT Wed Jul 20 2022

IMPACTS:
 -Gusty SW gradient winds subsiding this evening
 -Scattered evening storms

DISCUSSION:

After a bit of delay due to 850 hPa capping, convection has fired
just northwest of KHNB within the last hour.  We expect this
convection to continue to move southeastward this evening and mainly
affect KHNB initially.  Overall convective coverage is uncertain
this evening but will plan on putting in a period of VCTS at
KBWG/KSDF/KLEX to account for storms ahead of the front.  Most of
the activity should diminish after 21/06Z with skies clearing and
winds shifting to the NW.

CONFIDENCE:

Medium on all elements.

&&

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

Mesoscale.....MJ
Short Term....KDW
Long Term.....ALL
Aviation......MJ

Hazardous Weather Outlook
National Weather Service Louisville KY
910 PM EDT Wed Jul 20 2022

INZ076>079-083-084-089>092-KYZ023>043-045>049-053>057-061>067-
070>078-081-082-220115-
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
910 PM EDT Wed Jul 20 2022 /810 PM CDT Wed Jul 20 2022/

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

.DAY ONE...This Evening and Overnight.

Scattered thunderstorms will be possible across the outlook area
this evening and should diminish later tonight. Some of the storms
could be strong to severe with locally damaging winds to most likely
severe weather hazard. Heavy rainfall and some small hail will also
be possible.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Heat could approach dangerous levels Saturday and Sunday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be required this evening.

GENERAL STORM MOTION OF THE DAY:

Storms this evening will move from west to east at 20-25 mph.

Any users of this storm motion must be aware that thunderstorm activity
can be erratic and constantly evolving.  Please use this with caution
and be prepared for changing conditions.

&&

More information, along with other weather, hydrological and
climate information can be found, at weather.gov/louisville.

MJ/KDW

Special Weather Statement
National Weather Service Louisville KY
1052 PM CDT Wed Jul 20 2022

KYZ074-076-210430-
Metcalfe KY-Barren KY-
1052 PM CDT Wed Jul 20 2022

...A strong thunderstorm will impact portions of central Barren and
southwestern Metcalfe Counties through 1130 PM CDT...

At 1052 PM CDT, Doppler radar was tracking a strong thunderstorm over
Glasgow, moving east at 25 mph.

HAZARD...Wind gusts up to 50 mph and nickel 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...
  Edmonton.

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.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3692 8614 3705 8608 3706 8607 3705 8560
      3683 8565
TIME...MOT...LOC 0352Z 283DEG 21KT 3697 8591

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...50 MPH

MJ

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