textproduct: Indianapolis

KEY MESSAGES

- Strong to severe storms this evening into tonight, greatest threat after midnight

- Generally dry Thursday and Friday with low rain chances Thursday afternoon

- Near record warm temperatures expected through Saturday with multiple days in the 80s and lows in the 60s

- Much cooler Sunday into early next week with the potential for frost

DISCUSSION (This evening through Wednesday)

Issued at 103 PM EDT Wed Apr 15 2026

Overview.

An active and progressive spring pattern remains firmly in place across the Ohio Valley with a weak MCV moving across northern Indiana and a broader surface low currently across Iowa. This system is embedded within a broad southwesterly flow regime that is characterized by an 80-90 kt upper-level jet. As the LLJ ramps up this evening into tonight, thunderstorms are expected with the potential for damaging wind gusts with the strongest storms. While a brief period of ridging will bring a temporary reprieve on Friday, a strong cold front is expected to sweep through the region on Saturday with additional thunderstorms expected. This transition will usher in a much cooler airmass for the early part of next week, introducing potential frost concerns for the local area.

Through Tonight.

The latest water vapor imagery and regional radar mosaics highlight an MCV currently moving through northern Indiana. This feature is expected to remain north of the forecast area with a dissipating boundary closer to the I-70 corridor. Recent high-resolution model guidance keeps the convection this afternoon north of the forecast area associated with the MCV with additional development across Missouri and western Illinois towards 18-20Z as skies gradually clear and instability increases. Diabatic heating is already pushing temperatures into the upper 70s with dewpoints in the low 60s. This environment should yield MLCAPE values of 1200 to 1800 J/kg by peak heating. Effective bulk shear of 35-45 kts will be sufficient for organized multicellular structures if convection can hold together as it moves further into Indiana after 00Z.

The primary threat with this activity will be damaging wind gusts. High DCAPE values exceeding 800 J/kg and steep low-level lapse rates will support efficient downward momentum transfer in collapsing cores. A secondary round of convection is likely as the LLJ cranks up to 40-50 kts after 06z. This will sustain elevated convection through the overnight hours, though the severe threat should gradually wane as the boundary layer stabilizes after sunset.

Thursday through Friday Night.

The aforementioned MCV is forecast to exit to the east by late this evening, leaving behind a trailing surface trough. While scattered showers remain possible on Thursday, the overall trend will be toward drying as subsidence increases across the region. Friday looks to be the warmest and driest as strong warm air advection ahead of the next major trough pushes 850mb temperatures toward the 90th percentile of climatology. Highs in the low to mid 80s are probable, and record high minimums in the 60s are also at risk as a humid airmass remains entrenched across the state.

Saturday through Wednesday.

GEFS and EPS output shows high confidence in a significant pattern shift beginning on Saturday. A deep longwave trough will eject out of the Rockies, and ensembles are in good agreement on a strong cold front crossing Indiana during peak heating. Given the robust dynamics associated with this system, another round of severe weather is possible, although timing differences between the faster GFS and slower ECMWF solutions still need to be resolved. On the backside of the front, a 1030mb surface high will slide south from Central Canada. Ensemble means indicate temperatures dropping 15-20 degrees below normal for Sunday and Monday. Lows Sunday night and Monday night are currently projected to be in the low to mid 30s. Those with sensitive vegetation should prepare for potential frost or freeze headlines as the seasonably cold air settles in. The EPS members suggest a gradual moderating trend by Tuesday and Wednesday as the high shifts east, returning the region to southwesterly flow and more tranquil conditions to start the mid- week period.

AVIATION (18Z TAF Issuance)

Issued at 103 PM EDT Wed Apr 15 2026

Impacts:

- Southwesterly wind gusts to 30kts through the TAF period - Low chances for TSRA as early as 23Z, more likely after 06Z - MVFR cigs and MVFR to IFR vsbys during convection

Discussion:

VFR conditions expected for much of the TAF period with increasing chances for MVFR cigs during and after periods of convection that could begin as early as 23Z. Convection chances look low through much of the evening hours but as the LLJ ramps up during the late evening and overnight, convection chances will increase. Confidence is highest in the 06Z to 11Z timeframe with cigs dropping to around 015 during periods of convection. Southwesterly winds will frequently gust up to 30kts through 00Z, then more towards 20 to 25kts after 00Z through the remainder of the TAF period.

IND WATCHES/WARNINGS/ADVISORIES

None.