textproduct: Indianapolis

KEY MESSAGES

- Patchy fog possible through daybreak with additional fog development possible late tonight

- Scattered to numerous showers and storms are expected this afternoon into tonight

- Localized flash flooding will be possible this afternoon into tonight, isolated severe storms are also possible

- Generally drier late this week through early next week, but there is a chance for showers and storms late Friday into Saturday

DISCUSSION (Today through Tuesday)

Issued at 312 AM EDT Wed Aug 19 2026

Today through tonight...

Patchy fog will be possible through daybreak as winds remain very light across central Indiana. Any fog that develops should quickly mix out in typical diurnal fashion. Regional radar mosaic depicts an MCS currently moving across eastern MO and western IL. This system will continue to propagate southeastward along an instability gradient, keeping precipitation mostly confined to southwest portions of the forecast area through the morning. Isolated thunderstorms cannot be ruled out given weak elevated instability.

Greater chances for convection are expected this afternoon into tonight as a mid-upper level wave pushes across the region. At the surface, a weak west to east oriented cold front should gradually push south providing greater low-level convergence. These features along with daytime heating over an abundantly moist environment supports the potential for scattered to numerous showers and thunderstorms. Convection could continue well into the overnight, but expect generally decreasing coverage late tonight as the the strongest forcing shifts east.

Deep-layer wind shear is supportive for organized convection, but there remains some uncertainty on the degree of destabilization later today which limits confidence on the overall severe threat. Isolated damaging wind gusts or severe hail appear possible if sufficient destabilization occurs as favorable deep-layer wind shear could support multicell line segments and possibly even a few transient supercells.

The greater concern appears to be localized flash flooding given soils remain very saturated from recent rainfall. Model guidance continues to suggest the potential for training storms with the west to east oriented cold front slowly pushing south. Warm rain processes and PWATs around or over 2 inches will also promote efficient rainfall rates. Latest CAMs generally suggest the potential for 1 to 3 inches of rain where training occurs. Additional fog development is possible late tonight once convection dissipates.

Thursday through early next week...

Surface high pressure building in will provide mostly quiet weather conditions Thursday and Friday. A few upper level disturbance will move in late Friday into Saturday supporting at least low rain chances with sufficient moisture advecting into central Indiana. Long range guidance generally depicts surface high pressure building in once again late weekend into early next week providing mundane weather conditions. Expect temperatures to remain slightly below normal during the period.

AVIATION (06Z TAF Issuance)

Issued at 312 AM EDT Wed Aug 19 2026

Impacts:

- Patchy fog possible at LAF, HUF, BMG through 12Z today.

- Scattered to numerous showers and thunderstorms possible, mostly after 18Z.

Discussion:

Patchy fog is possible through 12Z today, mainly at the outlying TAF sites. A shortwave trough approaching from the northwest is expected to bring scattered to numerous showers and thunderstorms to central Indiana this afternoon into the evening hours. Some uncertainty remains regarding timing, and thus a Prob30 group was included to cover this potential initially after 18Z.

A TEMPO was included for some sites from 00-04Z this evening when greater coverage can be expected. Convection could linger during much of the overnight, but uncertainty remains. Fog development also appears possible late overnight if convection clears out. Winds should increase from the WSW as the shortwave approaches later today with speeds remaining under 10kt. Look for winds to become northeasterly tonight.

IND WATCHES/WARNINGS/ADVISORIES

None.