textproduct: Indianapolis

KEY MESSAGES

- Flood Watch in effect from 2PM Today through 8AM Thursday across the northern half of central IN with localized flash flooding possible

- Scattered to numerous showers and storms are expected this afternoon into tonight, isolated severe storms are possible

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

FORECAST UPDATE

Issued at 1141 AM EDT Wed Aug 19 2026

Isolated light showers are tracking across parts of south-central Indiana. Later today, another round of showers and storms are expected to move in from the northwest which could produce a swath of 1-2" of rain from this afternoon through tomorrow morning. The question is still where exactly the highest rain amounts fall, but north of Indy is where models continue to highlight. If enough rain falls within the White River basin, points along the river within Indy could back into Action Stage with an outside chance of a brief return to minor flooding by this weekend possible.

Outside of the flooding, some isolated areas of severe weather will be possible this afternoon to evening with damaging winds and hail the main threats. Given how saturated the ground is across the forecast area, even sub-severe winds could lead to tree damage.

Made a few adjustments to the PoPs to better match ongoing isolated showers and minor tweaks to the late day PoPs.

DISCUSSION (This afternoon through Tuesday)

Issued at 618 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 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 supports the potential for multicell line segments and possibly even a few transient supercells.

The greater concern will 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. A Flood Watch is in effect from 2 PM today through 8 AM Thursday across the northern half of central Indiana where training storms over saturated soils appears most likely. 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 (12Z TAF Issuance)

Issued at 618 AM EDT Wed Aug 19 2026

Impacts:

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

- Fog development possible tonight

Discussion:

Patchy fog cannot be ruled out 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 through tonight. 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 during the 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 and clouds clear out. Winds should increase slightly 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

Flood Watch through Thursday morning for INZ021-028>031-035>049- 054>057.