textproduct: Indianapolis

KEY MESSAGES

- Scattered thunderstorms possible today with the potential for strong to severe storms, primarily across far SE portions of central Indiana

- Damaging wind gusts are the primary threat, but large hail, localized flooding, and an isolated tornado threat are also possible

- Noticeably cooler and less humid for the second half of the week

FORECAST UPDATE

Issued at 916 AM EDT Tue Jul 21 2026

Surface analysis late this morning shows low pressure over northern Ontario with a cold front that extended SW to NW Indiana and Central IL. Water vapor imagery shows an associated deep upper trough over Ontario, with a trough axis moving through the Great Lakes. Water vapor shows some storm development beginning over northern Indiana on the leading edge of some subsidence. Radar shows some scattered precipitation ahead of the front over NW Central Indiana and across northern Indiana. Mainly SW flow was in place across central Indiana with high dew point values in the lower 70s.

The cold front is expected to progress southeast across Central Indiana late this morning and this afternoon. The air mass ahead of the front remains warm and humid, favorable for convective development. Forecast soundings early this afternoon show favorable CAPE ahead of the front along with high pwats over 1.9 inches. HRRR continues to suggest convective development through the late morning and early afternoon hours, particularly across eastern parts of Central Indiana within the warm sector ahead of the front. Given recent radar trends and the ingredients in place, thunderstorm development is expected. Will focus high pops mainly across the east and southeast parts of the forecast area. HIgh temperatures this afternoon should be reached early, and precipitation and a change in air mass should allow temperatures to fall back to the lower 80s in the afternoon.

DISCUSSION (Today through Monday)

Issued at 304 AM EDT Tue Jul 21 2026

Today through tonight...

Current KIND Radar imagery depicts quiet weather conditions across central Indiana as weak surface ridging remains in place. Upstream convection is ongoing across portions of MO/IL with an approaching system. Look for the disturbance along with an associated cold front to move in later today promoting scattered thunderstorm development, primarily from mid-morning into the afternoon hours. Moderate to strong destabilization ahead of the cold front and strengthening deep-layer wind shear supports the potential for severe thunderstorms.

Organized convection and supercells are expected with effective shear values around 35-50 kt, mainly over southeast portions of central Indiana as the cold front will likely move through the northwest half of the forecast area before sufficient destabilization occurs. Damaging wind gusts are the primary hazard, but large hail, localized flooding, and an isolated tornado threat also appear possible. Forecast soundings depict gradually veering low-level hodographs during the afternoon hours while a LLJ pushes through supporting the isolated tornado threat.

Look for the cold front and associated convection to quickly move out by the early evening hours. Cold air advection from surface high pressure building in behind the departing front will then promote quiet weather conditions. Expect cooler temperatures in the low to mid 60s overnight.

Wednesday through Friday night...

Another embedded shortwave and associated cold front will advect even cooler-drier air into the area late Tuesday night into Wednesday. Stronger surface high pressure building in favors quiet weather conditions during the period. Expect an upper wave approaching from the west on Friday to result in increasing mid-high clouds. Most guidance suggest subsidence induced dry air from the surface high should inhibit any precipitation chances from the weakening disturbance so will keep the forecast dry. Look for temperatures to remain cooler than normal with highs generally in the 70s to near 80F.

Saturday through early next week...

Long range guidance depicts weak surface high pressure remaining the dominant weather feature for much of the weekend providing mostly quiet weather conditions. Aloft, northwesterly flow should allow for a few shortwaves to pass through the region. These disturbances along with deeper moisture advecting into central Indiana will return low rain chances to the forecast at times late Sunday into early next week.

Diverging model solutions leads to lower confidence in exact details towards the end of the period. Widespread severe weather is not expected at this time, but ensemble guidance suggest at least moderate destabilization both Sunday and Monday afternoon. This along with enhancement of mid-upper level flow from the passing shortwaves could support a threat for severe weather. Uncertainty will remain high until models become better aligned.

Warm air advection ahead of the aforementioned disturbances should warm temperatures well into the 80s to possibly near 90F in some spots Sunday and Monday.

AVIATION (12Z TAF Issuance)

Issued at 644 AM EDT Tue Jul 21 2026

Impacts:

- Chance for TSRA at KIND/KBMG within 14Z-19Z, where brief MVFR/brief IFR will be possible - Brief MVFR ceilings cannot be ruled out 12Z-18Z outside of convection - Winds gradually veering through the period, gusting 17-21 kt today

Discussion:

Mainly VFR to prevail over central Indiana terminals through most of the TAF period with brief periods of MVFR possible within 12Z-18Z from both lower ceilings and at times scattered convection near KIND/KBMG, as slowly passing cold front -SHRA/isolated TSRA and associated lower decks progress from NW to SE.

Winds will slowly increase through the day with sustained flow of 8- 14KT and gusts to 17-21 kt possible during the day. Winds then diminish to 3-8KT by late this evening. Wind direction will veer through the period.

IND WATCHES/WARNINGS/ADVISORIES

None.