textproduct: Indianapolis

KEY MESSAGES

- Isolated to scattered storms again this afternoon and evening, severe weather is not expected

- Slow moving storms may produce pockets of flooding

- Gradual cooling trend through the week with daily chances for showers and storms

FORECAST UPDATE

Issued at 948 AM EDT Sun Jul 5 2026

A stubborn low stratus deck lingers over much of central Indiana this morning as deep moisture remains trapped beneath a shallow inversion. 13Z temperatures were in the lower 70s.

The ongoing forecast is in good shape for the rest of the day. Low pressure resides over the region and will drift only slowly east through this evening. As an upper wave axis pivots into the region from the west this afternoon...expect it to interact with the moist and unstable airmass across the Ohio Valley to generate scattered convection focused especially from mid afternoon into the evening. As stratus gradually lifts into a broken cu field...heating will promote increasing instability to around 2000 j/kg MLCAPE. In the absence of shear and with only modest lapse rates present... convection will largely remain disorganized and below severe levels later today. Torrential rainfall and localized flooding will serve as primary concerns with PWATS from 1.5 to 2 inches and sluggish storm motions. Lightning will also be a factor once again for any outdoor activities.

The increased clouds will aid in finally giving the region a break from the excessive heat of the last several days. Low level thermals support highs mainly in the mid and upper 80s this afternoon. Zone and grid updates out.

DISCUSSION (Today through Saturday)

Issued at 131 AM EDT Sun Jul 5 2026

Overview.

Scattered afternoon and evening thunderstorms are expected for today and Monday amid continued warm and humid conditions, albeit not as warm as the last few days. A stronger cold front mid-week will bring more widespread rain chances to central Indiana, followed by a transition to much cooler and drier weather for the latter half of the week.

Through Daybreak.

Patchy to areas of fog will continue through the night with some pockets of locally dense fog. The combination of residual moisture from the afternoon and evening storms is combining with widespread condensation nuclei from firework debris/smoke to enhance the fog potential. This fog will generally remain non-dense at 1-3 miles, but some fog-favored areas such as valleys may see periods of dense fog through 8AM.

Today Through Monday.

Central Indiana will remain positioned on the northern periphery of a suppressed sub-tropical ridge centered over the Gulf Coast states, leaving the local area under a weak northwest flow regime aloft. The boundary layer will remain characterized by high moisture content, with surface dew points lingering in the low to mid 70s. Combined with daytime ambient temperatures rising into the low 80s in the north and upper 80s in the south, a moderately unstable airmass will develop each day. MLCAPE values are forecast to reach 2000 to 2500 J/kg during peak heating.

Given the absence of strong, large-scale synoptic forcing, convective initiation will depend heavily on mesoscale features, such as residual outflow boundaries from previous convection and localized differential heating zones. Consequently, convective timing will be primarily diurnal, maximizing between 19Z and 02Z each afternoon and evening. Kinematic support remains weak, with 0-6 km bulk shear values under 15 knots, ensuring an unorganized, outflow-dominant pulse storm mode. Soundings indicate that while instability is lower than previous days, precipitable water values around 1.8 to 2.0 inches and steep low-level lapse rates will still support localized heavy downpours and transient downbursts capable of isolated wind damage. The primary forecast uncertainty revolves around spatial coverage, as convective-allowing models continue to diverge on exactly where mesoscale boundaries will focus development. Convection should diminish rapidly each evening with the loss of solar insolation.

Tuesday Through Saturday.

The multi-day synoptic transition will begin on Tuesday as a brief period of shortwave ridging ahead of a developing northern stream system keeps scattered, mainly diurnal convective chances in place. By Wednesday, a potent, high-amplitude longwave trough is forecast to dig out of south-central Canada and phase into the Great Lakes region. This feature will drive a sharp surface cold front southward across Indiana Wednesday afternoon and evening. Robust large-scale ascent combined with strong linear low-level convergence along the front will support a high probability of widespread showers and thunderstorms. While deep-layer shear is modeled to increase ahead of the trough axis, the overall severe weather potential will depend on the precise timing of the frontal boundary and the magnitude of pre-frontal destabilization.

In the wake of the frontal passage, an airmass exchange will occur Thursday through Saturday. High-amplitude troughing will establish itself over the eastern United States, while a strong Canadian high pressure center builds southward into the Midwest. This will lead to some cold air advection across the Ohio Valley, gradually bringing a cooler and drier continental air mass. High temperatures for the late-week period will drop into the lower 80s, which is slightly below seasonal averages. That trend looks to continue into early next week with dew points dropping into the 50s and highs near 80.

AVIATION (18Z TAF Issuance)

Issued at 1154 AM EDT Sun Jul 5 2026

Impacts:

- Improvement to VFR this afternoon and evening. - Low confidence for additional showers and storms this afternoon - Potential for additional MVFR to IFR cigs/vsbys tonight

Discussion:

Low pressure over NW Indiana was continuing to provide weak cyclonic flow across the area along with plentiful MVFR cloud cover. Daytime heating should allow the low cloud to dissipate, leading to some isolated afternoon CU development. HRRR shows widely scattered showers and storms with this feature late this afternoon and evening. However, confidence is low at this time as cloud cover is limiting daytime heating and we are running cooler then model temperature trends.

Any storms will dissipate after sunset, however cyclonic along with lingering lower level moisture will once again allow for MVFR/IFR cigs to form overnight with fog.

IND WATCHES/WARNINGS/ADVISORIES

None.