Special Weather Statement, NWS Indianapolis, IN

Area Forecast Discussion
National Weather Service Indianapolis IN
450 PM EDT Tue Jul 7 2020

.UPDATE...
The Aviation Section has been updated below.

&&

.SYNOPSIS...
Issued at 124 PM EDT Tue Jul 7 2020

A very warm and humid air mass will remain over Central Indiana
through Friday. This will result in daily chances for afternoon
showers and thunderstorms along with above normal temperatures.

A brief break in the hot weather is expected this weekend before
reverting back to the hot and humid pattern early next week.

&&

.NEAR TERM /Tonight/...

Issued at 124 PM EDT Tue Jul 7 2020

Surface analysis early this afternoon shows a large but poorly
organized area of high pressure over Illinois and Indiana. A warm
and humid air mass remained in place across the forecast area with
dew point temps in the lower 70s. GOES16 shows CU popping across
Central Indiana and radar is beginning to light up with isolated
showers and storms. Aloft water vapor shows ridging in place
across the southwestern states...steering the upper flow and any
associated forcing across the upper midwest and Great Lakes.

Little change is expected tonight in the overall pattern. Ongoing
diurnal showers and storms are expected to diminish as heating is
lost later today. Will still need to carry a few hours of evening
showers and storms possible through 00Z...but will drop pops
rapidly after that as all forcing mechanisms are lost...trending
toward partly cloudy skies. Will keep overnight lows close to
persistence.

&&

.SHORT TERM /Wednesday through Friday/...

Issued at 124 PM EDT Tue Jul 7 2020

Wednesday and Wednesday night look quite similar to the past few
days as the warm and humid air mass will remain in place across
Central Indiana. Models indicate a rather stagnant flow aloft.
Thus will continue the trend of afternoon and evening showers and
storms. This diurnal storm development is supported by forecast
soundings showing over 2400 J/KG of CAPE...pwats over 1.7 inches
and attainable convective temps. Again after heating is lost in
the evening...dry weather will return.

On Thursday the upper flow begins to change a bit as a short wave
is suggested to begin an approach on Central Indiana from IA.
Again...the very warm and humid air mass will be in play ahead of
this extra forcing. This combined with an easily triggered air
mass should result in more showers and thunderstorms on Thursday
afternoon and evening. Since the best forcing looks to arrive on
Thursday evening...we will hold onto pops a little longer on
Thursday evening than the past few nights. Overall there remains
little change in the air mass.

The GFS shows the short wave still exiting the area on Friday
Morning as the upper flow is suggested to become more northerly as
the day progresses. This is leads to some subsidence in the
afternoon in the wake of the upper wave and this is seen within
the forecast soundings and the mid and upper levels are
considerably dry by Friday afternoon than the previous few days.
Pwats fall under 1 inch by late Friday. Thus for now will focus
best pops on Friday during the earlier part of the day when upper
support is expected to be present. Will trend highs on Friday a
bit cooler also as NW surface flow takes shape late in the day in
the wake of the upper wave.

&&

.LONG TERM /Friday Night through Tuesday/...
Issued at 250 PM EDT Tue Jul 7 2020

The strong upper level ridge will retrograde into the southern
Rockies late week into the weekend...with a northwest flow regime
aloft taking hold over the Upper Midwest...Great Lakes and Ohio
Valley through this weekend. At least initially in the wake of the
primary upper wave late Friday...additional ripples in the flow
aloft will warrant at least a chance for scattered convection
again Saturday and possibly Sunday too.

By early next week...drier conditions will develop as the region
resides between the ridge to the west and a developing upper low
to the east. The upper low appears poised to cutoff from the mean
flow by the middle of next week across the central Appalachians...
and its presence to our east will slow the eastward expansion of
the heat ridge until later next week. Expect a cooler and less
humid surge of air this weekend into early next week with highs
focused in the mid and upper 80s. Daytime temperatures in the 90s
are set to return by next Tuesday and Wednesday with height rises
in advance of the ridge expansion. Still appears potential exists
for the heat to really turn up by late next week with mid to
upper 90s in play if model trends hold.

&&

.AVIATION /Discussion for 072100Z TAF Issuance/...
Issued at 450 PM EDT Tue Jul 7 2020

With the earlier update, added TSRA at KIND due to radar and
satellite loops and adjusted the winds. Still looking at VCTS for
the remainder of the evening through about 1z, with potential for
development pretty much any time. Previous discussion follows...

VFR conditions expected through the forecast period.

More of the same in this stagnant summer pattern that has set up
across the Ohio Valley. Cu has popped with the convective temp
being met along with widely scattered storms. Both should grow in
coverage through the afternoon and will handle simply with a VCTS
at all terminals. Any direct impact by convection to a terminal
will produce brief restrictions and will update with tempo groups
as needed.

Skies will clear tonight with loss of heating before doing this
all over again on Wednesday. Expect diurnal cu and convection to
develop again by midday. Winds will be light and variable
throughout the period.

&&

.IND WATCHES/WARNINGS/ADVISORIES...NONE.

&&

SYNOPSIS...Puma
NEAR TERM...Puma
SHORT TERM...Puma
LONG TERM....Ryan
AVIATION...Ryan/CP

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Special Weather Statement
National Weather Service Indianapolis IN
133 PM EDT Tue Jul 7 2020

INZ047-048-071815-
Hancock IN-Marion IN-
133 PM EDT Tue Jul 7 2020

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN HANCOCK AND
NORTHEASTERN MARION COUNTIES UNTIL 215 PM EDT...

At 133 PM EDT, Doppler radar was tracking a strong thunderstorm near
Lawrence, or 11 miles east of Indianapolis. This storm was nearly
stationary.

Nickel size hail and wind gusts up to 50 mph will be possible with
this storm.

Locations impacted include...
Indianapolis, Lawrence, Greenfield, Cumberland, McCordsville, New
Palestine and Spring Lake.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 3972 8603 3989 8600 3989 8576 3972 8585
TIME...MOT...LOC 1733Z 275DEG 4KT 3980 8592

Ryan

Special Weather Statement
National Weather Service Indianapolis IN
218 PM EDT Tue Jul 7 2020

INZ047-048-071900-
Hancock IN-Marion IN-
218 PM EDT Tue Jul 7 2020

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN HANCOCK AND SOUTHERN
MARION COUNTIES UNTIL 300 PM EDT...

At 217 PM EDT, Doppler radar was tracking a strong thunderstorm near
Beech Grove, or 9 miles east of Indianapolis. This storm was nearly
stationary. Additional storms were developing to the southwest
of this storm along the outflow over southern Marion County.

Nickel size hail and wind gusts up to 50 mph will be possible with
any of these storms.

Locations impacted include...
Indianapolis, Greenwood, Beech Grove, Speedway, Southport,
Cumberland, New Palestine, Warren Park, Homecroft and Monument
Circle.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 3970 8595 3964 8595 3963 8623 3977 8624
      3982 8592 3970 8587
TIME...MOT...LOC 1817Z 264DEG 2KT 3974 8597

Ryan

Special Weather Statement
National Weather Service Indianapolis IN
410 PM EDT Tue Jul 7 2020

INZ055-056-072045-
Johnson IN-Shelby IN-
410 PM EDT Tue Jul 7 2020

...SIGNIFICANT WEATHER ADVISORY FOR WESTERN SHELBY AND EASTERN
JOHNSON COUNTIES UNTIL 445 PM EDT...

At 409 PM EDT, Doppler radar was tracking a strong thunderstorm near
Franklin, or 12 miles west of Shelbyville, moving east at 15 mph.

Penny size hail and wind gusts up to 50 mph will be possible with
this storm.

Locations impacted include...
Shelbyville, Greenwood, Franklin, New Whiteland, Whiteland,
Bargersville, Fairland, Marietta and Boggstown.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 3938 8610 3956 8617 3968 8582 3942 8572
TIME...MOT...LOC 2009Z 258DEG 14KT 3952 8600

CP

Special Weather Statement
National Weather Service Indianapolis IN
427 PM EDT Tue Jul 7 2020

INZ046-047-072100-
Hendricks IN-Marion IN-
427 PM EDT Tue Jul 7 2020

...SIGNIFICANT WEATHER ADVISORY FOR EAST CENTRAL HENDRICKS AND
WESTERN MARION COUNTIES UNTIL 500 PM EDT...

At 426 PM EDT, Doppler radar was tracking a strong thunderstorm near
Speedway, or 7 miles southwest of Indianapolis, moving east at 5 mph.

Half inch hail and wind gusts of 50 to 55 mph will be possible with
this storm.

Locations impacted include...
Indianapolis, Greenwood, Plainfield, Beech Grove, Speedway,
Southport, Avon, Meridian Hills, Clermont, Homecroft, Rocky Ripple,
Williams Creek, Wynnedale, Spring Hill, Crows Nest, North Crows Nest,
Monument Circle, Indianapolis Int'l Airport, and Camby.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 3990 8614 3965 8602 3963 8610 3963 8634
      3978 8643
TIME...MOT...LOC 2026Z 249DEG 6KT 3973 8626

CP

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