textproduct: Indianapolis

KEY MESSAGES

- Hot and humid through at least mid week, with daily chances for showers and storms...especially through Friday morning

- Multiple rounds of severe storms will be possible from early today through at least Wed night...w/damaging winds, heavy rainfall/flash flooding the primary threats

FORECAST UPDATE

Issued at 916 AM EDT Mon Aug 10 2026

Surface analysis late this morning shows southwest flow in place across Indiana. This was due to a weak trough of low pressure stretched from northern Michigan to IA and NRN KS and strong high pressure in place across the southeastern states. GOES19 shows a thunderstorm cluster over NRN Ohio, while a wave of clouds and light rain were found over MI, pushing into IL. Scattered clouds were still found across central Indiana. Dew points were quite high, in the lower 70s. Aloft, water vapor shows mainly a NW flow in place. streaming from MT and WY, across the upper midwest, before slipping slightly south to the southern Great Lakes and northeastern states.

Models through the day show the NW flow to remain in place aloft. Weak embedded short waves within this flow will continue to be possible triggers for TSRA development, particularly across northern parts of the forecast area, closest to the ongoing flow aloft. Models continue to show uncertainty with positioning and timing of these waves, but for the moment, best timing looks to be this evening and late tonight. Latest ACARS soundings show a weak CAP in place at the moment, but plenty of CAPE aloft, over 2000 J/KG. Forecast soundings show even more, and very deep CAPE over 4000 J/KG available this afternoon, but still, a CAPE remains at that time near 800mb. HRRR fails to show much development through the afternoon and peak heating hours. Thus there appears to be many dry hours ahead through the late morning and afternoon hours, but an isolated TSRA late this afternoon cannot be ruled out due to the strong potential instability aloft. Thus will focus some minimal pops through the mid to late afternoon. Given our very warm air mass in place highs in the lower 90s appear on target.

MESOSCALE UPDATE

Issued at 306 AM EDT Mon Aug 10 2026

Smaller yet severe mesoscale convective complex currently crossing into northwest Indiana will enter northern portions of the IND CWA through pre-dawn hours. While overall slow weakening is expected, damaging winds are possible for the Lafayette area and east...with non-zero chances of isolated large hail or a brief, weak tornado. This convection is expected to cross northern counties through 13Z.

Previous mesoscale discussion follows...

Fairly robust convective development has occurred in the past 90 minutes over northwest Illinois along and south of a quasi- stationary front and at the nose of a WSW 25-35KT low level jet associated with a weak shortwave disturbance aloft. Sufficient effective deep layer shear exists in and upstream of central Indiana to support storm organization, with the most likely scenario being initial supercells growing upscale into one or more line segments that push eastward, then gradually more east/southeastward with time through the night. Significant uncertainty exists with how far southward the influence of the complex will extend, but roughly the northeastern third to half of the area, along and NE of the I-74 corridor, appear to have the greatest threat for strong to severe storms during the overnight hours.

Modest effective SRH values suggest a non-zero tornado threat, but upscale growth will likely support primarily an isolated damaging wind threat, and strongly supportive environmental factors (PWAT values around climatological 90th percentile, high freezing levels/deep warm rain processes, and possibly training convection along the upshear flank of the system) will support a threat for heavy rainfall and localized flooding as well. HREF local probability matched means show potential for isolated 1-3 inch amounts, with higher amounts possible in the strongest cores or if/where training occurs.

DISCUSSION (Today through Sunday)

Issued at 316 AM EDT Mon Aug 10 2026

Early today through Wednesday...

Central Indiana will continue to rest amid the northeastern edge of a predominant subtropical ridge occupying most of southern North America...with seasonably modest northwest flow aloft and associated small/weak forcings...maintaining chances of occasional convective clusters. Additionally, a weaker yet broad trough of surface low pressure aligned from the central Plains across the northern Midwest, will promote moderate southwesterly breezes...bringing very warm to hot conditions and increasingly oppressive humidity into the mid-week.

The resultant higher theta-E will contribute to instability gradient, although this will likely be strongest along the local region's far northern/NE zones...if not even closer to the southern Great Lakes. Therefore convective chances within the CWA will be greatest following upstream development (northern IL) that then trends/curls SE-ward. Best chances for organized/severe storms will most likely be Tuesday PM-overnight hours, and again late Wednesday...with general focus I- 74 corridor and northeast, with lowest confidence on severe potential over southwest counties.

That said, cannot rule out isolated RW-s at overall less favorable times given the warm/humid boundary layer...including isolated thunder later today north of a Lafayette to New Castle line, and across much of the CWA tonight. Expect temperatures through Wednesday to range from 68-75F to 85-93F, with a distinct NNE-SSW gradient, which may be increased by greater cloud cover over NE counties Tue-Wed.

Thursday through Monday...

Remainder of the period to most likely feature see-saw of conditions as quasi-stationary surface cool front along the northern side of very broad and very humid subtropical ridge...probably slides south by late Thursday, placing the region in milder easterly flow...with the boundary expected to then push north, returning humid southerly flow for the weekend. Most periods to yield at least low POPs per the corresponding frontal zone never really pushing south of the CWA, although overall convective chances after Thursday night should be much lower than the early/mid-week. Readings to range from mainly 60s to 80s.

AVIATION (18Z TAF Issuance)

Issued at 1250 PM EDT Mon Aug 10 2026

Impacts:

- Convection possible around and after 00z this evening, best chances from LAF to IND northward.

- South-southwest winds gusting to near 20KT this afternoon.

Discussion:

Mainly VFR conditions this TAF period. High uncertainty regarding precipitation chances due to warm and humid air in place with ACARS soundings showing minor capping in place near 875mb. As peak heating is reached this afternoon, Isolated convection cannot be ruled out through the later afternoon and evening, although any coverage should be quite limited.

Better forcing may arrive overnight, mainly impacting LAF and IND as best dynamics should be found across northern Indiana. HRRR suggests best chances for development will remain north of of TAF site and be limited to the overnight hours. Thus have included a VCSH mention for the evening and overnight hours just due the very low confidence for possible storm development.

IND WATCHES/WARNINGS/ADVISORIES

Heat Advisory until 8 PM EDT this evening for INZ051>053-060>062- 067>070.