textproduct: Indianapolis

KEY MESSAGES

- Hot and humid conditions through Monday

- One or more thunderstorm complexes possible tonight into Monday night, with damaging winds and heavy rainfall the primary threats, though uncertainty on exact details remains high

- Temperatures nearer normal and less humid mid week

FORECAST UPDATE

Issued at 1020 PM EDT Sun Jul 26 2026

Latest update has overall dropped convective chances through the overnight with both limited storm initiation so far over Upper Midwest and reflection thereof in latest CAMs....with a better opportunity for at least 1-2 storm complexes from midday Monday and especially later on into Monday night. Near term threat will maintain couple showers and non-severe TRWs along a NNW-SSE axis from near Sullivan down to Washington and west through 04Z which may include an isolated 40-50 mph gust per highest towers up to 20-25 kft. Stray convection may linger over these far-west/ southwest zones into the overnight where 3000+ J/kg MUCAPE will nudge eastward from Illinois. Despite light winds, dewpoints in generally the low to mid-70s will guide overnight temperatures...with lows by early Monday ranging from 68 in Winchester to 74 in Vincennes.

DISCUSSION (This evening through Sunday)

Issued at 340 PM EDT Sun Jul 26 2026

This Afternoon into Monday Night...

A highly uncertain forecast scenario remains the case again today, particularly with respect to the severe thunderstorm threat from late today into Monday night, with multiple scenarios on the table. As is often the case with these depth of the warm season setups, the exact evolution of each convective round will be largely thermodynamically driven and heavily influenced by the prior rounds, resulting in low confidence in the exact details as time goes on.

A volatile airmass is in place this afternoon to our southwest across the mid Mississippi and far lower Ohio Valleys, along and west of a frontal zone, characterized by temperatures in the mid 80s to mid 90s and dewpoints as high as the low 80s, resulting in MLCAPE values near 5000 J/kg, along with modest to strong effective shear values of 25-40KT overlapping. This should promote thunderstorm development late this afternoon into this evening as a subtle upper level disturbance slides southeast along the periphery of the upper level ridge, and this activity may nudge into the southwestern portions of the forecast area this evening. Will stick with chance PoPs for now, as it is unclear how far east this activity will make it, as the instability gradient will likely result in storm motion with a largely southerly component, and substantial convective inhibition remains across central Indiana on the milder side of the cloud-reinforced differential heating frontal boundary.

Additional severe convection is likely to develop over the upper Midwest, and this activity could make it into central Indiana as early as the pre-dawn hours Monday, though the unfavorable diurnal timing may limit the severe threat should this come to pass. With both of these possible rounds of thunderstorms, damaging winds would be the primary concern. Trimmed high temperatures back a couple/few degrees with low clouds and fog impacting morning insolation. Clouds are beginning to scatter out however, so do not expect nearly as strong an impact to high temperatures as what occurred yesterday, with the mid to upper 80s still well in reach today, and perhaps even a 90 degree reading sneaking into our far southwest.

Partly cloudy skies can be expected this afternoon with warm and humid conditions driving heat index values into the 90s across portions of the area.Another round of convection appears likely to initiate somewhere over the upper Great Lakes tomorrow afternoon associated with an upper level shortwave and surface cold front, again likely dropping southerly along an instability gradient in a continued volatile airmass characterized by ample shear and instability, along with precipitable water values at times in the vicinity of 2 inches. This will present again a primarily damaging wind threat, though an isolated tornado cannot be ruled out. Additionally, the aforementioned moist airmass along with deep warm rain processes as the wet bulb zero height remains seasonably high will present a heavy rainfall and localized flash flood threat, limited by the relatively progressive nature of any thunderstorm complexes - but a fairly strong westerly low level jet ahead of the cold front could produce some regeneration/training potential on the western flank of any MCS depending upon cold pool orientation.

Temperatures will have the potential to soar well into the 80s or low 90s on Monday afternoon, though this, too, is uncertain as any early day convective debris cloudiness could limit the impact of warm advection and insolation - the more sun, the greater the potential for highs getting to the 90 degree mark, which may couple with dewpoints well into the 70s to produce heat index values at or above 100 degrees Monday afternoon.

Tuesday onward...

Cold frontal passage Monday night into early Tuesday will bring temperatures back down much closer to seasonal normals from mid week onward, with a largely dry forecast until very late in the week as surface high pressure dominates the area. As the ridge aloft retrogrades slightly and the overall pattern amplifies, upper level disturbances late in the week may promote rain chances, though significant disagreement on these systems precludes more than a slight chance to low chance PoP in any one period from Friday into the weekend.

AVIATION (00Z TAF Issuance)

Issued at 646 PM EDT Sun Jul 26 2026

Impacts:

- Lingering MVFR ceilings at KBMG and KHUF possible this evening

- MVFR fog possible overnight

- Thunderstorms may impact KHUF for a short time late this evening

- Storm complexes may impact the area mid morning through mid afternoon and again Monday evening into the overnight

Discussion:

Lower clouds have been stubborn to mix out at both KBMG and KHUF but should see ceilings rise to VFR over the next few hours. Convection has fired quickly early this evening from south central Illinois southeast into western Kentucky along the instability gradient. This may drift east a bit this evening and potentially could see convection approach KHUF for a short time.

There remains a highly conditional thunderstorm threat late tonight and especially Monday morning as a storm complex over the upper Midwest dives into the region. Will maintain a PROB30 at all sites over a 6 hour window through early afternoon with confidence still too low to justify a more specific risk. Additional convection may impact the terminals through the rest of the day with the possibility for another complex Monday evening and night. Any storms that do impact the area will have the potential to be intense.

With plentiful low level moisture and light to calm winds tonight expect fog development again...though not quite to the same degree as this morning as mid and high clouds will work against radiational cooling. Will take the outlying sites down to 3-4SM. Winds will be fairly light and frequently variable through the period.

IND WATCHES/WARNINGS/ADVISORIES

None.