Severe Thunderstorm Warning 56, NWS Indianapolis, IN

Area Forecast Discussion
National Weather Service Indianapolis IN
309 PM EDT Tue Apr 2 2024

.KEY MESSAGES...

- Scattered to widespread showers and thunderstorms through mid-
morning; Primary convective threats are damaging wind gusts and
large hail with a few tornadoes possible.

- Flash Flood Watch in effect through Tuesday afternoon. Repeated
rounds of heavy rainfall. Additional 1 to 3 inches of rainfall is
possible, with locally higher amounts.

- Severe thunderstorms are possible again late this afternoon
through early evening, with all severe hazards possible.

- A significant temperature drop is expected post frontal passage on
Tuesday evening. Potential impacts in the cold sector include
scattered snow showers and overnight frost/freeze.

- Rain/Snow chances on Thursday

- Dry and cool Friday through Sunday Morning

- Rain chances return Sunday afternoon through Monday Morning

- Dry on Tuesday

- Early forecast thoughts on the April 8th eclipse covered in the
  CLIMATE section at the bottom

&&

.SHORT TERM (This evening through Wednesday)...
Issued at 308 PM EDT Tue Apr 2 2024

All eyes in the short term period are on severe weather potential
this afternoon. On the synoptic scale, a very positively tilted
trough axis extends from the Great Lakes southwestward to
northwestern Mexico. A secondary shortwave trough is currently
diving southward out of Mexico, and is in the beginning stages of
phasing with the larger trough. This phasing is inducing rapid
cyclogenesis over Missouri and Illinois, and the resulting low
pressure system is responsible for today's severe weather potential.
Additionally, gusty non-convective winds upwards of 35 to 45 mph are
possible this afternoon. We have issued a Wind Advisory through 8pm
across our northwestern counties to accommodate this.

CONVECTIVE POTENTIAL AND HAZARDS

In the low's buoyant warm sector, storms across southern Illinois
are rapidly developing in a surface-based environment. The
environment is characterized by strong shear at all levels, steep
lapse rates, and abundant low-level moisture. MLCAPE values are
between 1000-1500 J/Kg, effective shear is over 50 knots, and
hodographs are long and straight. Some curvature in the 0-1km layer
exists from the Ohio River southward into Kentucky. At least
initially, the primary threat appears to be large hail. This could
be mitigated by a shear vector nearly parallel to the initiating
boundary...which would encourage line segments and storm clusters,
and therefore competition between numerous hail embryos.

A tornado threat may gradually evolve, especially as one heads
further south and east where the greater low-level curvature exists
in the hodographs. Though, given the magnitude of 0-1km shear (20 to
30 knots), it wouldn't take much to induce rotation closer to the
surface. Still, there are some inhibiting factors for tornado
potential on the Indiana side of the severe threat area. Aside from
the greater influence of crosswise vorticity, some low-level
stability from earlier convection remains across central Indiana.

The potential for strong damaging winds likely also increases with
time, as the 850mb low-level jet intensifies. Simply put, there will
just be more momentum for downdrafts to transfer to the surface. Per
SPC sounding analysis, dry air remains in the mid-levels, so this
downward transfer process could be quite efficient.

TONIGHT AND WEDNESDAY

By tonight, the system's cold front will be through and strong cold
air advection begins. Temperatures are expected to fall into the 30s
by morning. Precip chances increase again towards morning as
moisture wraps around the back side of the low while it occludes
just north of us. Thermal profiles suggest that snow may mix in at
times during the day Wednesday. Accumulations are not currently
expected, mainly due to very marginal surface temperatures and
insufficient rates to overcome a very warm ground. Some graupel is
possible at times as a shallow layer of instability develops in the
afternoon. Additionally, a tight MSLP gradient will help induce
gusty winds through the day Wednesday (up to 35 mph).

&&

.LONG TERM (Wednesday night through Tuesday)...
Issued at 308 PM EDT Tue Apr 2 2024

Thursday...

Models show a deep, closed upper low expected to be over Ohio on
Thursday morning. This is a large system, that will impact weather
across the eastern half of the United States. Strong cyclonic flow
will be in place across Indiana through the course of the day. An
associated surface trough axis will be found stretching across PA to
lower MI, poised to push across Central Indiana through the course
of the day. Forecast soundings on Thursday, as this cyclonic upper
flow remains in place, show saturated mid and lower levels, with
much of the column below freezing. Thus a mix of rain and snow or
just snow will be possible. Forecast soundings reveal steep lapse
rates with attainable convective temperatures, favorable for precip
development. With pwats rather low, only around 0.40 inches each
day, precip amounts will be light, however confidence for precip
will be high given the moisture and forcing signals. Thus a high
pop, but low amount of precip, type forecast will be expected.

Ongoing cold air advection will be in play on Thursday, resulting in
below normal temperatures, with highs only in the 40s.

Friday through Sunday Morning...

By Friday morning the upper pattern will have become highly
amplified. The previous deep upper low will have moved east toward
New England, while another deep trough and upper low moves into the
western CONUS, over California. This results in a sharp ridge in
place aloft over the plains. This feature will provide subsidence to
Central Indiana along with cool northwesterly flow. Forecast
soundings show a relatively dry column through the weekend as the
strong ridge axis slowly passes across the region by late Sunday
morning.  This will result in partly cloudy and cool temperatures,
below seasonal normals. As we progress from Friday to Saturday and
Sunday, expect a slow warming of daily high temperatures. This will
be due to the gradual eastward progression of the ridge aloft and
the associated area of high pressure, slowly shifting east through
Sunday and allowing the arrival of warmer southerly winds by Sunday.
Thus daily highs around 50 on Friday should rise to around 60 by
Sunday.

Sunday Afternoon through Monday Afternoon...

The previously mentioned west coast upper low is expected to
progress toward the plains by Sunday, pushing a warm front into the
Ohio Valley on Sunday Night. Southwest flow aloft ahead of the upper
low is suggested to provide upper forcing amid a diffluent flow. This
will be a favorable pattern and signal for showers and thunderstorms
through Monday morning as an associated negatively tilted upper
trough axis passes across Central Indiana through Monday. Thus
chances for showers and storms will need to be included at that
time. A speedier passing of this upper trough would probably result
in less cloud cover on Monday afternoon, while a slower passing
would result in more cloud cover at that time. For more
information/discussion on Monday afternoon cloud coverage see the
CLIMATE section.

Tuesday...

Here the models continue to suggest a continuation of a quick moving
spring like pattern across Central Indiana and the Ohio Valley. A
quick moving ridge is expected to pass on Tuesday, with forecast
soundings showing a dry column and subsidence in place. Thus a dry
forecast at that time for now.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 110 PM EDT Tue Apr 2 2024

Impacts:

- Scattered to numerous showers and scattered thunderstorms through
  20Z-22Z
- Ceilings mostly MVFR and worse
- Southerly winds shifting to westerly this evening.
- Wind gusts to 40+ knots possible.

Discussion:

Radar trends early this afternoon shows scattered to widespread
convection found within the warm sector across southern central
Indiana. These showers and storms will continue to impact IND/BMG
and HUF through the first 3-4 hours of the TAF period. LAF was found
north of the warm front and with its easterly flow there,
trajectories of current precipitation should keep Thunder away from
LAF.

HRRR suggests the scattered convection across the area impacting the
TAF sites will continue through the mid to late afternoon. Thus have
used a large window of VCTS at most TAF sites, along with a tempo
group to account for prevailing, stronger storms that may strike a
TAF site.

Cold front east of St. Louis marching east will mark the end of the
thunder event. Cold air advection amid westerly flow is expected to
result in trapping stratocu by this evening and continued MVFR Cigs
overnight.

A moderate pressure gradient in the wake of the front will allow for
gusty winds overnight. Wind gusts to near 30 mph will be possible.

&&

.CLIMATE...
Issued at 300 PM EDT Mon Apr 1 2024

It is now about a week out from eclipse day and as stated in
previous iterations of this discussion, a few signals can be
deciphered from long range guidance.

As mentioned in the discussion above, a deepening/occluding low
pressure system is anticipated to develop over the eastern US. As
this low deepens, it should act to bottle up the upstream wave
pattern. This can be seen in guidance as a deepening trough over the
western US. It's this trough that could be the determining factor as
to what kind of weather we see on Monday April 8th.

Taking a step back, global teleconnections show strongly negative
phases in both the NAO and AO. This means that the synoptic scale
will dictate our weather going forward, and with a very strong and
occluded low over the east coast...it is likely that the position
and longevity of this system will determine the evolution of the
west coast trough.

Latest ensemble guidance depicts both the eastern and western
troughs becoming highly amplified with an increasingly squeezed
ridge in between. A flow pattern similar to a classic omega block
looks to take shape by Friday. With strongly negative
teleconnections, a pattern featuring blocking is not a surprise.
Guidance begins to diverge over the weekend as models struggle to
depict how the aforementioned features interact within the bottled up
flow. Guidance typically struggles in blocking patterns, and can be
too fast with synoptic-scale features. This can be seen in recent
trends with today's system that has been gradually shifting westward
with time.

It's tough to downscale this pattern into a cloud cover forecast for
the 8th. The primary questions are how much does the occluded east
coast low affect the upstream pattern, and in what form the western
trough ejects eastward. As guidance comes into greater consensus,
the answers to these questions will likewise come into focus. Stay
tuned for further updates.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 8 PM EDT this evening for INZ028-035-043-044-
051.

Flood Watch until 8 PM EDT this evening for INZ042>049-051>057-
060>065-070>072.

&&

SHORT TERM...Eckhoff
LONG TERM...Puma
AVIATION...Puma
CLIMATE...Eckhoff

Hazardous Weather Outlook
National Weather Service Indianapolis IN
323 PM EDT Tue Apr 2 2024

INZ021-029>031-036>042-045>049-052>057-060>065-067>072-031930-
Carroll-Tippecanoe-Clinton-Howard-Montgomery-Boone-Tipton-Hamilton-
Madison-Delaware-Randolph-Putnam-Hendricks-Marion-Hancock-Henry-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, Greencastle, Plainfield,
Brownsburg, Danville, Indianapolis, Greenfield, New Castle, 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
323 PM EDT Tue Apr 2 2024

This hazardous weather outlook is for central Indiana.

.DAY ONE...Through Tonight.

Weather hazards expected...

 Lightning, large hail, damaging wind gusts, isolated tornadoes,
 heavy rain and flooding

DISCUSSION...

Thunderstorms will move across central Indiana at times through
this evening. Severe storms are possible. Windy conditions are
expected away from thunderstorms this afternoon and evening as
well.

In addition, heavy rain may lead to flooding.

Storm movement will be from the west and southwest 40 to 50 mph.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Rainfall totals of up to around 2 inches through Wednesday will lead
to an increased flooding threat.

Freezing temperatures are possible for all or parts of the area
during the early mornings of Thursday into Sunday.

.SPOTTER INFORMATION STATEMENT...

 Spotter activation may be needed at times today.

&&

This product in graphical format...along with other weather...
hydrological and climate information...at:

http://www.weather.gov/erh/ghwo?wfo=ind
http://www.weather.gov/ind

INZ028-035-043-044-051-031930-
Warren-Fountain-Vermillion-Parke-Vigo-
Including the cities of Williamsport, West Lebanon, Attica,
Covington, Veedersburg, Clinton, Fairview Park, Rockville,
Montezuma, Rosedale, and Terre Haute
323 PM EDT Tue Apr 2 2024

This hazardous weather outlook is for central Indiana.

.DAY ONE...Through Tonight.

Weather hazards expected...

 Lightning, large hail, damaging wind gusts, isolated tornadoes,
 heavy rain and flooding

DISCUSSION...

Thunderstorms will move across central Indiana at times through
this evening. Severe storms are possible. Windy conditions are
expected away from thunderstorms late this afternoon and evening as
well.

In addition, heavy rain may lead to flooding.

Storm movement will be from the west and southwest 40 to 50 mph.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Rainfall totals of up to around 2 inches through Wednesday will lead
to an increased flooding threat.

Freezing temperatures are possible for all or parts of the area
during the early mornings of Thursday into Sunday.

.SPOTTER INFORMATION STATEMENT...

 Spotter activation may be needed at times today.

&&

This product in graphical format...along with other weather...
hydrological and climate information...at:

http://www.weather.gov/erh/ghwo?wfo=ind
http://www.weather.gov/ind

Special Weather Statement
National Weather Service Indianapolis IN
144 PM EDT Tue Apr 2 2024

INZ037-039-045>047-052>054-021815-
Clay IN-Owen IN-Morgan IN-Putnam IN-Hendricks IN-Boone IN-
Hamilton IN-Marion IN-
144 PM EDT Tue Apr 2 2024

...Strong thunderstorms will impact portions of central Morgan,
Hendricks, central Clay, northern Owen, western Marion, southeastern
Boone, southern Hamilton and southeastern Putnam Counties through 215
PM EDT
...

At 144 PM EDT, Doppler radar was tracking strong thunderstorms along
a line extending from 7 miles west of Danville to 9 miles southeast
of Brazil. Movement was northeast at 70 mph.

HAZARD...Wind gusts up to 50 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

Locations impacted include...
Indianapolis, Carmel, Fishers, Noblesville, Plainfield, Brownsburg,
Zionsville, Speedway, Greencastle, Mooresville, Danville, Westfield,
Avon, Pittsboro, Cloverdale, Meridian Hills, Brooklyn, Clermont,
Monrovia, and Clayton.

This includes the following highways...
 Interstate 65 between mile markers 114 and 130.
 Interstate 70 between mile markers 28 and 78.
 Interstate 74 between mile markers 57 and 73.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3986 8668 4007 8593 3943 8645 3931 8719
TIME...MOT...LOC 1744Z 244DEG 63KT 3975 8665 3939 8704

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH

KF

Preliminary Local Storm Report
National Weather Service Indianapolis IN
151 PM EDT Tue Apr 2 2024

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

0429 AM     Tstm Wnd Dmg     Lake Lemon              39.27N 86.39W
04/02/2024                   Monroe             IN   Public

            Thunderstorm winds lifted and flipped boat
            and blew down softwood pines on north side
            of Lake Lemon. Appears to be microburst.
            Time estimated by radar.

&&

AGM

Special Weather Statement
National Weather Service Indianapolis IN
215 PM EDT Tue Apr 2 2024

INZ039>041-046>049-054-021845-
Morgan IN-Henry IN-Hendricks IN-Madison IN-Delaware IN-Hancock IN-
Hamilton IN-Marion IN-
215 PM EDT Tue Apr 2 2024

...Strong thunderstorms will impact portions of southern Madison,
western Hancock, southwestern Delaware, north central Morgan,
southeastern Hendricks, northwestern Henry, Marion and southern
Hamilton Counties through 245 PM EDT
...

At 215 PM EDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Noblesville to near Plainfield. Movement
was northeast at 70 mph.

HAZARD...Wind gusts up to 50 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

Locations impacted include...
Indianapolis, Muncie, Anderson, Carmel, Fishers, Noblesville,
Lawrence, Plainfield, Greenfield, Beech Grove, Speedway, Mooresville,
Southport, Westfield, Avon, Yorktown, Cumberland, McCordsville,
Pendleton, and Fortville.

This includes the following highways...
 Interstate 65 between mile markers 103 and 124.
 Interstate 69 between mile markers 200 and 238.
 Interstate 70 between mile markers 56 and 103.
 Interstate 74 between mile markers 70 and 98.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3970 8589 3958 8656 3999 8620 4025 8535
TIME...MOT...LOC 1815Z 244DEG 60KT 4001 8597 3968 8641

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH

KF

Special Weather Statement
National Weather Service Indianapolis IN
237 PM EDT Tue Apr 2 2024

INZ067-021900-
Knox IN-
237 PM EDT Tue Apr 2 2024

...A strong thunderstorm will impact portions of Knox County through
300 PM EDT
...

At 237 PM EDT, Doppler radar was tracking a strong thunderstorm near
Albion, moving northeast at 80 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 hail damage to vegetation is
         possible.

Locations impacted include...
Vincennes, Bicknell, Oaktown, Monroe City, Wheatland, Bruceville,
Decker, and Vincennes University.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3848 8775 3851 8765 3855 8767 3859 8761
      3864 8762 3870 8752 3878 8749 3882 8753
      3890 8741 3874 8725 3869 8728 3868 8725
      3861 8724 3850 8749 3850 8753 3852 8754
      3845 8760 3846 8766 3843 8767 3841 8774
TIME...MOT...LOC 1837Z 234DEG 67KT 3839 8794

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

KF

Special Weather Statement
National Weather Service Indianapolis IN
259 PM EDT Tue Apr 2 2024

INZ060-061-067>069-021930-
Daviess IN-Knox IN-Martin IN-Greene IN-Sullivan IN-
259 PM EDT Tue Apr 2 2024

...A strong thunderstorm will impact portions of southeastern
Sullivan, Knox, northwestern Martin, western Greene and northern
Daviess Counties through 330 PM EDT
...

At 259 PM EDT, Doppler radar was tracking a strong thunderstorm over
Vincennes, moving northeast at 85 mph.

HAZARD...Wind gusts up to 50 mph and penny size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

Locations impacted include...
Vincennes, Linton, Bloomfield, Bicknell, Odon, Lyons, Elnora, Monroe
City, Wheatland, Bruceville, Plainville, Sandborn, Edwardsport, Switz
City, Newberry, Crane, Freelandville, Vincennes University, and Burns
City.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3859 8764 3859 8761 3861 8763 3862 8762
      3864 8762 3867 8759 3868 8754 3869 8753
      3871 8752 3874 8750 3876 8750 3913 8705
      3887 8678 3852 8757 3858 8764
TIME...MOT...LOC 1859Z 233DEG 72KT 3867 8751

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH

KF

Special Weather Statement
National Weather Service Indianapolis IN
326 PM EDT Tue Apr 2 2024

INZ053-055-061>063-067>070-022000-
Johnson IN-Daviess IN-Brown IN-Knox IN-Owen IN-Martin IN-Lawrence IN-
Greene IN-Monroe IN-
326 PM EDT Tue Apr 2 2024

...Strong thunderstorms will impact portions of Monroe, southwestern
Johnson, western Brown, eastern Knox, southern Owen, Martin, eastern
Greene, western Lawrence and Daviess Counties through 400 PM EDT
...

At 326 PM EDT, Doppler radar was tracking strong thunderstorms along
a line extending from 6 miles east of Bloomfield to near Oakland
City. Movement was northeast at 75 mph.

HAZARD...Wind gusts up to 50 mph and penny size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

Locations impacted include...
Bloomington, Bedford, Washington, Bloomfield, Shoals, Ellettsville,
Loogootee, Odon, Oolitic, Lyons, Elnora, Monroe City, Wheatland,
Plainville, Montgomery, Newberry, Crane, Cannelburg, Alfordsville,
and Smithville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3851 8700 3850 8706 3854 8711 3852 8715
      3855 8720 3851 8730 3854 8735 3854 8737
      3851 8737 3854 8739 3853 8742 3908 8701
      3939 8615 3869 8657 3869 8668 3853 8668
      3853 8683 3849 8688 3851 8693 3849 8695
TIME...MOT...LOC 1926Z 239DEG 64KT 3903 8682 3838 8737

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH

KF