textproduct: Indianapolis

KEY MESSAGES

- Scattered to numerous showers tonight

- Below normal temps to continue through the weekend with frost likely Saturday and Sunday

- Slow warm up with rain returning early next week, potential for heavy rain at times

FORECAST UPDATE

Issued at 959 PM EDT Thu Apr 30 2026

Showers continue ahead of a low pressure system, with showers now having arrived into the northwest forecast area. Most showers were light, with visibilities at or above 7 miles, but a few stronger cells were around, especially back with the cold front in Illinois.

Forecast is in decent shape, so mainly tweaked hourly PoPs to match recent trends. While there is some weak instability near the cold front, which is likely currently helping the stronger cells, weakening lapse rates will help lower the odds of thunder. Thus, feel the odds of thunder will be less than mentionable and have removed thunder mention.

Forecast low temperatures look reasonable so made no significant changes.

DISCUSSION (This evening through Thursday)

Issued at 127 PM EDT Thu Apr 30 2026

Overview.

Central Indiana will experience a persistent period of below-normal temperatures through the upcoming weekend as a deep upper-level trough remains anchored over southeast Canada. While scattered light showers and isolated rumbles of thunder are possible through this evening, the primary focus shifts toward a significant frost threat for Saturday and Sunday mornings as surface high pressure settles over the region. Looking into next week, a transition to a more active and humid pattern is expected as the synoptic flow shifts, bringing an increasing threat of heavy rainfall by midweek.

This Evening through Saturday Night.

The current mesoscale environment is defined by a lingering northwesterly flow behind a departing frontal boundary, with high- resolution model guidance such as the HRRR and NAM indicating a weak shortwave ripple moving along the broader cyclonic flow. While low- level moisture is limited, a narrow window of mid-level saturation and modest lapse rates around 7 C/km will support spotty showers and perhaps a few isolated thunderstorms late this evening, though instability remains too meager for any severe concern. As the shortwave exits, residual mid-level moisture will keep clouds across the area through near daybreak which will keep temperatures slightly more mild with lows in the low to mid 40s. Friday will be dry and seasonably cool, but by Saturday morning, the proximity of a surface high-pressure ridge will promote better radiational cooling conditions. With areas of frost expected along and north of the I-74 corridor with a low-end potential for a freeze near Muncie and areas to the northeast. Radiational cooling becomes most favorable on Sunday morning as the axis of the surface high pressure moves directly over central Indiana, resulting in nearly calm winds and clear skies. This setup will allow the boundary layer to decouple efficiently, with high confidence in widespread frost as temperatures bottom out in the lower 30s across most of the forecast area with the main uncertainty being the timing of the shift to stronger southerly flow which could advect just enough warm air to limit frost formation.

Sunday through Thursday.

Another dry day is expected for Sunday with southerly flow gradually strengthening ahead of the pattern shift for early next week. Transitioning into Monday and Tuesday, the high pressure departs to the east, allowing for a slow warming trend as low-level flow turns southerly and begins to draw moisture from the Gulf of Mexico. Broad ensemble runs, including the GEFS and ECMWF, highlight a deepening longwave trough over the Central Plains by Wednesday, which will significantly increase precipitable water (PWAT) values toward 1.40 to 1.60 inches. This surge in moisture, combined with a quasi- stationary frontal boundary draped across the Ohio Valley, creates a notable threat for heavy rain and training convection toward the end of the period. Current probabilistic guidance suggests a 20-30% chance of rainfall totals exceeding 2 inches in some basins, necessitating a close watch on river levels and potential flash flooding concerns for the middle of next week.

AVIATION (00Z TAF Issuance)

Issued at 645 PM EDT Thu Apr 30 2026

Impacts:

- Showers tonight at times - MVFR ceiling after 06Z, low chance of IFR - Isolated gusts to 20kt Friday afternoon

Discussion:

Scattered to numerous showers will move across the sites mainly in the 03-09Z time frame. Brief visibility restrictions to MVFR are possible in the showers. Most coverage will be at KLAF/KIND. Odds of thunder are too low to mention.

VFR ceilings will become MVFR overnight, and these ceilings will persist into the mid-morning to early afternoon at KLAF/KIND. Cannot rule out brief IFR ceilings, but odds are not high enough to include.

Winds will become west then northwest overnight into Friday morning.

IND WATCHES/WARNINGS/ADVISORIES

None.