Indiana’s Weather For Tuesday

HEADLINES
– Showers and storms today, with a break for a few hours in the midday.
– A few severe storms possible for Central and South Central Indiana this afternoon and evening.
– Below normal temperatures through the week with light rain chances continuing tomorrow and Thursday
– Shower chance Race morning.

RACE DAY SUNDAY
Partly to mostly cloudy, spotty showers, mainly in the morning.
East/north-east wind 5-10 mph.
– 6am 51
– 9am 55
– 12pm 63
– 3pm 68

TODAY’S MAP

NWS TECHNICAL DISCUSSION

An active, rainy day ahead for all of Central Indiana. Widespread
showers and storms expected this morning with additional chances for
thunderstorms again this afternoon and evening.

This morning...

This morning an area of low pressure is over the Central Plains with
a warm front extending from near Kansas City to Evansville, IN.
Strong upper level diffluence ahead of a jet streak rounding the
base of a negatively tilted trough places much of the Ohio Valley in
an area of enhanced lift. A 30-45 kt SSW low level jet is pumping
ample moisture northward over the warm front and maintaining
effective bulk shear values of 40-55kts within this warm sector.
This set up has resulted in a large complex of showers and storms
ahead of the low along the warm front and triple point. Satellite
and radar imagery depict the large area of convection over the
majority of Illinois at this hour, pushing north and eastward toward
Indiana. Short term guidance keeps the warm front south of Central
Indiana through the morning hours, potentially reaching up into
Southwest Indiana around Knox County, where a few storms could be
strong this morning with gusty winds as the main threat. Further
north for the majority of Central Indiana, the lower levels should
remain stable enough to inhibit surface based severe storm
development; however elevated instability and shear should be enough
to support convective showers and elevated thunderstorms with heavy
rain, flooding, and lightning as the main threats.

PW rising to near 1.60-1.80 inches this morning, in addition to
strong moisture advection northward and skinny CAPE aloft are a good
recipe for very heavy rainfall. Nearly unidirectional flow aloft
and a northward component to storm motion may lead to the
possibility of training storms over the same areas this morning and
a localized flash flooding threat. HREF localized probability
matched mean QPF through this evening shows widespread 1.00-1.50"
inches of rain for Central Indiana with localized higher amounts of
2.00-3.00 for portions of South Central and Southwest Indiana.

This afternoon and evening...

Hi-res guidance indicates the warm sector of the aforementioned low
will overspread the southwestern half of Central Indiana. While the
chances for renewed convection this afternoon and evening appear
likely, the severe threat does look conditional with marginal
confidence on severe weather. Will have to watch if the atmosphere
can recover after the morning round of showers and storms exist the
state mid to late morning. Any dry breaks allowing for boundary
layer heating early to mid afternoon should allow for the atmosphere
to destabilize enough to support a few strong to severe storms this
afternoon and evening. Nearly uniform SW flow from 925mb to 300mb
suggest storm clusters or line segments are favored. Long hodographs
do suggest the potential for a few discrete cells or supercells
along and south of the warm front as well which could produce an
isolated tornado. The primary threats with any storm are damaging
wind gusts and localized flooding. Relatively weak low-level shear
may tend to limit the overall tornado threat. Look for showers and
storms to diminish in coverage overnight as stronger forcing shifts
east.

BUFKIT cross sectional profiles indicate saturated low levels
through the overnight hours tonight, despite the best forcing for
ascent and storm threat shifting east. Would not be surprised to see
leftover showers persist into the overnight hours especially along
and north of I-70 closer to the low.

.Wednesday...

Cold air advection aloft and waves of energy wrapping around the
upper trough within a saturated environment will support scattered
showers and a few storms through the day on Wednesday, and
especially during peak heating of the day. Steep low level lapse
rates during the afternoon may support an isolated lightning threat.
Severe weather is not expected. Clouds and showers with cold air
advection will keep temperatures below average for this time of year
with highs only in the 60s.

&&

.LONG TERM (Wednesday through Monday)...
Issued at 339 AM EDT Tue May 20 2025

A much cooler week ahead is in the forecast for Central Indiana with
highs struggling to get out of the 60s most days. Rain chances
remain highest through Thursday, then a few days of drier conditions
arrive for the first half of the week. Sunday is being monitored
very closely for Indianapolis as the threat for rain showers may be
increasing.

Troughing over the great lakes region with a slow moving surface low
over Lake Ontario will support cloudy, cool, and at times wet
conditions mid week. 850mb and surface temperature anomalies will be
well below normal for mid to late May as highs struggle to get out
of the low to mid 60s. Clouds and the presence of showers will keep
overnight lows slightly elevated, yet still below average in the mid
40s. Higher pressure moving overhead Friday and Saturday should
result in much drier conditions for the first half of the weekend
with clearing skies. A very cool airmass still remains overhead;
however stronger surface heating should allow for better low level
mixing and highs to make a run for 70 degrees.

There are also low chances for precipitation (30% or less) over the
weekend including Sunday, but confidence is lower due to diverging
model solutions. Most guidance shows a few complexes of storms
developing over The Plains and weakening as they propagate ESE.
There has been a shift in guidance over the past 24 hours, shifting
the storm track northward into Central and South Central Indiana for
the Sunday morning timeframe. Will continue to watch this trend and
adjust rainfall chances upward in later forecast issuances as
confidence increases.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 659 AM EDT Tue May 20 2025

Impacts:

- MVFR to IFR cigs and vis through the day, likely going up and down
depending on showers and storms

- E/SE winds 10-15kts, with sporadic gusts 20-25kts

- Multiple rounds of rain and storms today. Evening convection could
be severe

Discussion:

Multiple rounds of rain and storms expected today, with cigs and vis
likely bouncing between IFR and low VFR through the day. First round
of convection is beginning to push off to the east with leftover
lower clouds and showers around. Another round of showers is
expected midday, then another round of convection this evening. Due
to multiple rounds of showers and storms, exact timing of each
individual shower or storm is going to be difficult. Expect varying
conditions throughout the day.

There is likely to be a period with little to no rainfall mid
afternoon but renewed convective development will occur over eastern
Illinois and western Indiana by 19-21Z spreading east into the
evening. Winds will veer to southeast and remain gusty...with a
further veer to southwest by the evening as the cold front moves
through. There`s lower confidence if cigs and vis will briefly
become VFR midday in between rounds of convection as a low level
inversion may keep lower cigs and vis stuck near the surface. For
now, remaining pessimistic with the forecast through today.

INDY SEVEN DAY FORECAST
Today: Periods of showers and storms. A few could be severe. High 69.

Tonight: Showers and storms. A few could be severe. Low 58.

Wednesday: Scattered showers. High 66.

Wednesday Night: More scattered showers. Low 49.

Thursday: Partly to mostly cloudy, breezy and cooler. Isolated shower possible, mainly in the morning. High 60.

Thursday Night: Partly cloudy. Low 43.

Friday: Partly sunny. High 64.

Friday Night: Partly cloudy. Low 45.

Saturday: Partly sunny. High 67.

Saturday Night: Partly cloudy. Low 50.

Sunday: Mostly cloudy, with spotty showers, mainly in the morning. High 69.

Sunday Night: Mostly cloudy. Low 52.

Monday: Mostly cloudy. High 67.

NWS CHARTS FOR TODAY/TONIGHT