textproduct: Indianapolis

KEY MESSAGES

- Multiple rounds of showers and scattered thunderstorms today through Thursday night

- Isolated strong to severe storms are possible this afternoon and Thursday, damaging winds and heavy rain the main threats

- Sharply colder conditions arrive Friday, accompanied by northwest wind gusts of 30 to 40 mph

- Widespread frost is likely late Saturday night into early Sunday morning

DISCUSSION (Today through Tuesday)

Issued at 131 AM EDT Wed Oct 14 2026

Today Through Thursday.

An approaching upper-level shortwave trough over the northern Plains will flatten the downstream ridge, forcing a surface cold front to sag southward into central Indiana through the day. Gulf moisture will pool along and ahead of this boundary, driving PWAT values upward into the 1.4 to 1.7 inch range, which sits well above the 90th percentile for mid-October.

As of early this morning, elevated showers associated with the aforementioned moisture advection continues to move across northern Indiana and portions of Illinois. These showers may impact the northwestern counties, but otherwise expect convection to hold off until later in the day. Modest mid-level lapse rates will limit buoyancy with model soundings showing a skinny CAPE profile, but with SBCAPE values of 500 to 1200 J/kg updrafts will be strong enough to allow for thunderstorm development. Effective bulk shear around 35 to 45 kt will provide sufficient organization for multicell clusters and isolated transient supercell structures. The primary convective threats will be localized damaging wind gusts and brief torrential rainfall, though widespread severe weather is not expected given extensive cloud debris limiting stronger diurnal heating.

The frontal boundary will decelerate and oscillate across the region tonight as an open shortwave ejects northeastward from the middle Mississippi Valley. This will at least some convection through the overnight, but much less than during the daytime hours.

On Thursday, a deeper, amplifying mid-latitude trough over the Upper Midwest will induce surface cyclogenesis along the frontal wave, dragging a secondary, stronger cold front across central Indiana Thursday afternoon and evening. Pre-frontal warm sector recovery will support renewed thunderstorm development. While shear profiles remain strong with 0-6 km bulk shear exceeding 50 kt, thermodynamic profiles will be conditionally dependent on morning cloud clearance. Any pockets of surface heating will enhance low-level lapse rates, maintaining an isolated strong-to-severe risk along and ahead of the frontal line before dry slotting and strong cold advection scour out precipitation from west to east Thursday night.

Friday Through Tuesday.

A sharp pattern transition will occur Friday in the wake of the cold frontal passage as a broad, amplified longwave trough settles over the eastern half of the CONUS. Robust low-level cold air advection will cause 850mb temperatures to tumble from near +10C Thursday evening to between -2C and -4C by Friday afternoon. Efficient boundary layer mixing in steep low-level lapse rates, combined with a tight surface pressure gradient behind the departing surface low, will generate sustained northwest winds of 20 to 25 mph with frequent gusts of 30 to 40 mph Friday afternoon. Lingering stratocumulus under the cyclonic upper flow will keep daytime highs capped in the upper 50s.

A sprawling 1028-1030mb surface high pressure will build from the northern Plains into the lower Ohio Valley over the weekend. Diminishing winds and clearing skies Friday night will yield lows in the upper 30s but winds should remain just elevated enough through the night to avoid frost formation outside of very sheltered areas.

The primary frost and freeze concern arrives Saturday night into early Sunday morning. The surface ridge axis will center directly across central Indiana, setting up optimal conditions for radiational cooling with calm winds, a clear sky, and surface dewpoints dropping into the low 30s. Both deterministic GFS/ECMWF runs and the EPS/GEFS ensembles indicate high confidence in overnight lows dropping into the lower 30s across most of the area, with subfreezing minimums possible likely in traditional cold drainage areas. Frost headlines will likely be required for this period.

By Monday and Tuesday, the upper-level trough will lift into the Canadian Maritimes as low-amplitude ridging and quasi-zonal flow overspread the mid-Mississippi and Ohio Valleys. The surface high will shift toward the mid-Atlantic coast, establishing southerly return flow. Low-level warm air advection will drive 850mb temperatures back toward +8C to +10C, allowing daytime temperatures to moderate into the upper 60s and lower 70s. Subsidence under the surface ridge will ensure dry conditions across central Indiana through Tuesday ahead of the next upstream disturbance.

AVIATION (06Z TAF Issuance)

Issued at 131 AM EDT Wed Oct 14 2026

Impacts: - MVFR cigs after 18Z - Scattered convection, mainly from 18Z to 02Z - Wind shift from southwest to north after 17Z

Discussion:

High and mid clouds will increase into the overnight ahead of a cold front. Some scattered showers may impact LAF towards daybreak, but confidence is low. Greater storm coverage is expected for the afternoon hours, especially at HUF and BMG. Cigs will drop to MVFR with the arrival of showers and storms along with a wind shift from the southwest to north. There are some signs that cigs will drop to IFR late Wednesday night, but confidence is low that it occurs.

IND WATCHES/WARNINGS/ADVISORIES

None.