Severe Thunderstorm Warning 55, NWS Indianapolis, IN

Area Forecast Discussion
National Weather Service Indianapolis IN
305 PM EDT Sun Jun 25 2023

.Mesoscale Update...
Issued at 125 PM EDT Sun Jun 25 2023

Skies have quickly cleared across much of the forecast area as of
15Z with low to mid 80s already in the Wabash Valley. Higher
dewpoints continue to advect into the region as well from the
southwest. Starting to see the initial hints of cu formation across
northeast Illinois and northwest Indiana. Winds are already gusting
at 20-25mph as well.

LAPS sounding analysis showing a nice amount of instability present
above the inversion already to the tune of 2000-2500 j/kg with lapse
rates at an impressive 8C/km and higher across eastern Illinois and
western Indiana. To put it mildly...the atmosphere is quickly
aligning itself for the convective fireworks anticipated later this
afternoon.

The bulk of the 12Z data is now in and continues to support a high
end risk for severe storms focused over the eastern half of the
forecast area after 18-19Z. There remains fluctuations in exactly
where the initiation takes place but all signs point to somewhere in
the Kokomo-Marion to Indy metro zone continuing S/SW towards
Bloomington. Timing of initiation is critical. An earlier start
closer to 18Z would support west of the zone mentioned above while a
later start at 19-20Z would support in or just east of this zone.
The atmosphere should start providing clues on this timing over the
next 1-2 hours.

All severe risks are on the table but want to clarify level of
concern for each risk.

1) Large Hail (possibly 2"+): the amount of instability already in
the hail growth zone supports this as the primary risk out of the
gate as convection fires. And with the wind potential accompanying
the storms as well...we need to be talking more about the risk of
wind driven hail in the strongest cells.

2) Damaging Winds and Downbursts: The dry adiabatic flow already
present into the mid levels with steep lapse rates supports
convection having no problem pulling winds to the surface. Current
thinking is that while this will be a threat initially...it should
become the primary threat as storms grow upscale and mature into a
larger cluster...and that may not occur until after it moves out of
the forecast area.

3) A Few Tornadoes: not to diminish the tornado risk at all because
it is enhanced across our eastern counties this afternoon...but it
is not the main risk. Directional shear through 850mb is maximized
over eastern counties later this afternoon with the greatest concern
for tornadoes in a zone from northern Madison Co and Muncie area
south through Rushville and perhaps down to Greensburg then shifting
east into far eastern Indiana and western Ohio. This also correlates
to the area where supercells may remain discrete before congealing
further east. 0-1km SRH values will exceed 100 m2/s2 and combined
with available shear and instability makes a stronger tornado a
valid concern as well.

4) Flash Flooding: it seems weird to be mentioning this considering
the antecedent dry conditions but...there are likely to be
tremendous rainfall rates within the strongest storms. And one
factor many are not thinking about: torrential rainfall over a short
timeframe on dry soils actually could enhance runoff concerns.

One final non-convective risk to mention is the heat and humidity.
Temps expected to peak in the low to mid 90s with dewpoints in the
upper 60s and lower 70s will produce max heat indices in the 95-100
degree range. This does not meet Heat Advisory criteria...but it has
been since Summer 2022 since these heat indices were realized over
central Indiana. Be sure to take precautions for the heat this
afternoon as well.

The next Mesoscale Update will be around 1 pm or shortly after.
Pertinent portions of 934 AM Meso Discussion follows...

The atmosphere has provided clarity finally for the potential severe
threat this afternoon with higher confidence for significant impacts
focused especially across the eastern half of the forecast area. Lot
to get to this morning with the initial mesoscale update and more to
follow through the day.

One mitigating factor for convective coverage and intensity
discussed Saturday was the pocket of drier air noted in the 850-
800mb layer (and really up as high as 700mb) that was drifting
across the region during peak heating today. The overnight model
suite has shifted away from that being as much as a factor and
despite the presence of dry air within that layer noted on the KSTL
ACARS sounding this morning...the tendency to intensify the pocket
of dry air across the region has diminished from Saturday. The one
model that continues to struggle with this is the HRRR...likely the
reason for the hour to hour variability with convective development
noted over the last several hours. For all of its usefulness in
short term forecasting...one known caveat with the HRRR is that it
can overdo mixing within the boundary layer and that may be going on
here. Sounding analysis for mid afternoon over central Indiana shows
the HRRR on the low end of the range for expected surface dewpoints
as low as the mid 60s in some locations. Bulk of the model suite
focuses peak dewpoints more in the upper 60s and lower 70s which
appears quite reasonable.

That being said...the surge of drier near surface air into northern
Missouri is impressive in the mid 50s. As that advects E/NE really
appears that a rare psuedodryline setup could organize in the
vicinity of the cold front by this afternoon which would accentuate
rapid convective development. For instance...dewpoints immediately
behind the front drop into the 50s across the northern Wabash Valley
while low 70s reside over the eastern half of the forecast area.
This is just one more component that has trended towards a higher
confidence in severe convection by mid to late afternoon.

Clearing is rapidly expanding east through the western half of the
forecast area currently...with most if not all of central Indiana
enjoying sunshine by late morning. The KSTL ACARS earlier showed
850mb temps near 25C and that air is advecting in our direction.
Essentially...expect temperatures to warm rapidly as soon as the sun
gets out over the next few hours...with temps potentially knocking
on the door of 90 as early as 16Z in the lower Wabash Valley. While
some of the model guidance again is too aggressive...in our
opinion...in warming temps (HRRR again leads the pack here)...much
of the forecast area is going to make it into the low and possibly
mid 90s before convection initiation. With the dewpoints
expected...it will feel oppressive for the first time this year as
heat indices peak in the upper 90s in spots. Winds will become gusty
by late morning into the early afternoon.

This rapid warming will also enable highly unstable conditions to be
in play by mid afternoon with MLCAPEs in excess of 3000 j/kg...a
deep layer of dry adiabatic flow potential above 700mb and steep
lapse rates. As stronger forcing aloft in the mid and upper levels
pivots around the base of the upper low over the upper Midwest and
850mb flow strengthens...the setup is in place for explosive
convective development to take place in the 18-20Z timeframe in
vicinity of the front and dewpoint gradient. At this time...our
thoughts have not changed on that location to be somewhere across
the central part of the forecast area...from Kokomo to the Indy
metro perhaps down as far south as Bloomington.

Primary severe weather concerns remain focused on damaging winds and
downburst potential as well as significant hail. The steep lapse
rates and huge layer of dry adiabatic flow support the idea of
damaging winds and this is further supported by the impressive levels
of DCAPE in the vicinity of 1500 j/kg. The amount of instability in
the hail growth zone remains impressive as well with any intense
elevated core likely to have no trouble generating large hailstones.

That being said...there is a narrow axis where the tornado threat is
enhanced. As the afternoon progresses ahead of the front...our far
eastern counties should see surface flow back which will produce an
area where directional shear increases through about 850mb. Right
now...see the Muncie to Rushville zone as particularly susceptible
for this risk likely focused in the 19-22Z timeframe before flow
transitions to more unidirectional. Storms will shift E/SE into Ohio
and northern/central Kentucky shortly after 00Z with any severe
threat over for our area.

To recap...all severe weather modes are in play with a timeframe
from 18-00Z. Am most concerned for the eastern half of the forecast
area where all of the above parameters discussed align the best.
Remain prepared and diligent as storms will likely develop and
intensify quickly.

The next Mesoscale Update will be by late morning.

&&

.Short Term...(This evening through Monday)
Issued at 305 PM EDT Sun Jun 25 2023

* Strong to severe storms will continue this afternoon
* Chances for rain return mainly on Monday

For the details about the severe storms this afternoon, please see
the mesoscale discussions.

Tonight...

Much of if not all of the convection will be east of the area by
00Z. Will keep some low PoPs in the east and southeast early tonight
to cover stragglers.

Some additional showers may develop later this evening into the
overnight across mainly the northern forecast area in wrap around
forcing from the system. Will have some low PoPs there.

Lows tonight will be in the 60s.

Monday...

An upper level low near eastern Lower Michigan will swing a trough
through the area on Monday. Enough moisture will remain with the
system to generate scattered to numerous showers, mainly in the
afternoon when some instability builds. Highest PoPs will be in the
northeast, closest to the upper low.

Some thunder will be possible with the instability, but severe
storms are not expected.

Highs will be in the 70s northeast where more clouds will be to the
middle 80s southeast with more sun.

&&

.Long Term...(Monday night through Sunday)
Issued at 305 PM EDT Sun Jun 25 2023

Monday night into Tuesday...

The upper level low to the northeast will continue to influence the
northeast portions of central Indiana with chances for rain
continuing at times. Temperatures in these areas will remain cooler
than average. To the southwest, less influence from the upper low
will bring fewer clouds and temperatures in the 80s.

Tuesday night into Wednesday...

Surface high pressure will provide dry conditions during this
period. Temperatures will be near normal to a bit below normal in
the northeast.

Wednesday night through Friday...

An upper ridge will attempt to move east and influence the area, but
the axis will remain well west. This will put us on the edge and
allow any energy moving around the edge to perhaps bring some
scattered convection. Will have some low PoPs to account for these.

Temperatures will warm as the ridge gets closer, with highs warming
into the middle 80s to middle 90s by Friday, with warmest
temperatures in the southwest closest to the ridge's influence.

Friday night onward...

An upper low to the north of the area will influence the area along
with a low pressure system. Some timing questions remain, so will
just go with chance PoPs through this period. Temperatures will
remain warm.

&&

.Aviation...(18Z TAF Issuance)
Issued at 125 PM EDT Sun Jun 25 2023

Impacts:

* Convection developing shortly after 18Z with greatest impacts late
  this afternoon at KBMG and KIND

* Strongest storms may produce brief wind gusts to 50kts

* Dry after 22Z at all terminals

* Non thunderstorm wind gusts up to 25kts through early evening

* MVFR ceilings possible Monday morning

Discussion:

The region remains in a lull at the moment as the atmosphere
organizes for expected robust convective development to initiate
somewhere between 18-19Z ahead of an approaching boundary over
eastern Illinois. KHUF and very possibly KLAF will not be impacted
as convection likely fires east of those terminals. For KBMG and
KIND though...storms will impact between 19-22Z with the potential
for brief damaging wind gusts...large hail and very heavy rainfall.
With the highest confidence in impacts at KIND...will maintain a
tempo group and adjust as needed. Outside of any storms...southwest
winds will continue to gust to around 25kts at times...gradually
transitioning to westerly behind the boundary this evening before
diminishing.

For the overnight into Monday...skies will largely clear tonight
before expansion of MVFR stratocu towards daybreak as the cold pool
associated with the upper low approaches. Winds will become gusty
again Monday from the west with the potential for a few showers by
later in the afternoon.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&

Mesoscale...Ryan
Short Term...50
Long Term...50
Aviation...Ryan

Hazardous Weather Outlook
National Weather Service Indianapolis IN
328 PM EDT Sun Jun 25 2023

INZ021-029>031-036>042-044>049-051>057-060>065-067>072-261930-
Carroll-Tippecanoe-Clinton-Howard-Montgomery-Boone-Tipton-Hamilton-
Madison-Delaware-Randolph-Parke-Putnam-Hendricks-Marion-Hancock-
Henry-Vigo-Clay-Owen-Morgan-Johnson-Shelby-Rush-Sullivan-Greene-
Monroe-Brown-Bartholomew-Decatur-Knox-Daviess-Martin-Lawrence-
Jackson-Jennings-
Including the cities of Delphi, Flora, Lafayette, West Lafayette,
Frankfort, Kokomo, Crawfordsville, Lebanon, Zionsville, Tipton,
Fishers, Carmel, Noblesville, Anderson, Muncie, Winchester,
Union City, Farmland, Parker City, Rockville, Montezuma, Rosedale,
Greencastle, Plainfield, Brownsburg, Danville, Indianapolis,
Greenfield, New Castle, Terre Haute, Brazil, Spencer, Gosport,
Martinsville, Mooresville, Greenwood, Franklin, Shelbyville,
Rushville, Sullivan, Carlisle, Shelburn, Farmersburg, Linton,
Bloomfield, Jasonville, Worthington, Bloomington, Nashville,
Columbus, Greensburg, Vincennes, Washington, Loogootee, Shoals,
Bedford, Mitchell, Seymour, and North Vernon
328 PM EDT Sun Jun 25 2023

This hazardous weather outlook is for central Indiana.

.DAY ONE...Through Tonight.

A broken line of thunderstorms will move east across the area this
afternoon into early evening. Damaging winds and large hail will be
the main severe threats. A few tornadoes are possible as well. Severe
storms should be east of the area by 800 PM.

Storm motion will be from the west 30 to 40 mph.

Temperatures prior to the storms will warm into the lower and mid 90s
in much of the area with heat indices peaking close to 100 degrees in
some locations.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Thunderstorms will be possible at times through Tuesday and again
Thursday afternoon through Saturday. Lightning and brief heavy rain
will be possible.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is needed this afternoon and early evening.

&&

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

INZ028-035-043-261930-
Warren-Fountain-Vermillion-
Including the cities of Williamsport, West Lebanon, Attica,
Covington, Veedersburg, Clinton, and Fairview Park
328 PM EDT Sun Jun 25 2023

This hazardous weather outlook is for central Indiana.

.DAY ONE...Through Tonight.

A few thunderstorms remain possible this afternoon. Severe storms are
no longer expected, but any storm will be capable of producing gusty
winds, hail, and heavy rain.

Storm motion will be from the west 30 to 40 mph.

Warm and humid conditions will persist this afternoon.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Thunderstorms will be possible at times through Tuesday and again
Thursday afternoon through Saturday. Lightning and brief heavy rain
will be possible.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated.

&&

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

Preliminary Local Storm Report
National Weather Service Indianapolis IN
357 PM EDT Sun Jun 25 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0353 PM     Hail             4 WSW Plainfield        39.68N 86.45W
06/25/2023  E1.00 inch       Hendricks          IN   Public

            Report from mPING: Quarter (1.00 in.).

&&

ELB

Preliminary Local Storm Report
National Weather Service Indianapolis IN
400 PM EDT Sun Jun 25 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0356 PM     Hail             Washington              38.66N 87.16W
06/25/2023  E1.00 inch       Daviess            IN   Public

            The hail lasted about 5 min.

&&

ELB

Preliminary Local Storm Report
National Weather Service Indianapolis IN
401 PM EDT Sun Jun 25 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0359 PM     Hail             Gosport                 39.35N 86.66W
06/25/2023  E1.25 inch       Owen               IN   Public

            Report from mPING: Half Dollar (1.25 in.).

&&

ELB

Preliminary Local Storm Report
National Weather Service Indianapolis IN
402 PM EDT Sun Jun 25 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0400 PM     Hail             1 WNW Plainfield        39.71N 86.41W
06/25/2023  E0.50 inch       Hendricks          IN   Public

            Report from mPING: Half-inch (0.50 in.).

&&

ELB

Preliminary Local Storm Report
National Weather Service Indianapolis IN
403 PM EDT Sun Jun 25 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0350 PM     Hail             Washington              38.66N 87.17W
06/25/2023  E0.70 inch       Daviess            IN   Amateur Radio

&&

ELB

Preliminary Local Storm Report
National Weather Service Indianapolis IN
404 PM EDT Sun Jun 25 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0401 PM     Hail             1 W Cicero              40.12N 86.04W
06/25/2023  E0.25 inch       Hamilton           IN   Public

            Pea size hail 231st Street and Toll Gate
            Road, Hamilton County, 1 mile SW of Cicero.

&&

ELB