textproduct: Indianapolis

KEY MESSAGES

- Widespread minor/moderate river flooding continues south of I-70

- Locally heavy rainfall is expected tonight into Wednesday, which will exacerbate or prolong ongoing flooding

- Scattered severe storms with all hazards are possible tonight and Wednesday

- Record warmth today but cooler temperatures expected Thursday

FORECAST UPDATE

Issued at 826 AM EDT Wed Mar 11 2026

Surface analysis late this morning shows low pressure over SW MI. A cold front extended southwest from the low into NW Indiana and eastern IL. This placed much of Central Indiana still within the warm sector as temperatures at many locations continued to remain around 70. Radar shows a QLCS ahead of the front, pushing across western Central Indiana. Water vapor across the CONUS shows a moderate trough in place across the plains states, with moist southwest flow ahead of the trough streaming into the Ohio Valley.

This morning...the ongoing QLCS will make progress across Central Indiana along with a strong LLJ. HRRR suggests 850mb winds of 70 knts pushing quickly across the forecast area this morning, quickly driving the QLCS across Central Indiana. Given these strong winds aloft, severe threat remains valid for any winds that could mix down to the surface. HRRR suggests the stronger thunderstorms should exit the area near 11a-12p, but cold pool rain still may linger into the early afternoon. Thus continued high pops will be used for much of the day.

Additional development across southern and southeastern parts of Central Indiana will possible this afternoon as the front sags southward and begins to interact with the warmer and favorable airmass still in place to the south.

Given the cold air advection expected in the wake of the front, look for temperatures to fall into the 40s by late afternoon.

MESOSCALE UPDATE

Issued at 731 AM EDT Wed Mar 11 2026

An anomalously warm/moist air mass is in place across central Indiana this morning within strong warm advection regime. An upstream QLCS is oriented oblique to the deep shear vector, and given its magnitude it will be favorable for mesovortices and tornado potential. These will be most likely where cold pool-driven surges are most pronounced causing line reorientations to more north- south. From the apex of any bowing segments northward is where the highest threat of tornadoes will be this morning across central Indiana. Otherwise, damaging wind will be the primary threat particularly with any rear-inflow jet/surge structures, given weakly stable lower troposphere and strong momentum aloft (i.e., ~65-knot at 1-km) easily displaced downward to the surface.

SHORT TERM (Today and tonight)

Issued at 230 AM EDT Wed Mar 11 2026

Quiet conditions remain across central Indiana early this morning with gusty S/SW aiding in temperatures hovering near 70 degrees at 06Z. Convection up to this point has remained confined to the northwest of the forecast area in close proximity to the frontal boundary. The approach of a stronger surface wave...now located across northeast Missouri...has enabled storms to track further south over the last few hours into west central Illinois. This will be the area of convection to monitor for impacts across the forecast area after 09Z and continuing into the morning with the potential for additional storms during the afternoon.

Through Late Morning

The ongoing convection across central and western Illinois is highlighted by an impressive bookend vortex that is moving towards KBMI as of 06Z. Mesoanalysis shows the storms in this area are feeding off an environment with ample 0-3km CAPE overlaid by an area with stronger BL shear. A recent VAD profile from KILX also continued to show an impressive elongated right turn to the hodograph in the lowest 1-2km with SRH values in excess of 400 m2/s2 in the lowest 500m. Extrapolation of the bookend could end up clipping the northern Wabash Valley around 0730Z and will be the portion of the forecast area that will need to be most closely monitored over the next couple hours although it has showed a recent weakening trend.

The presence of the strong low level SRH values will support an isolated tornado risk with the bookend but the overall wind profile is not as supportive of a greater tornado threat being further away from the frontal boundary to the north. Remain more confident in damaging wind gusts becoming the primary risk as these storms move into our northwest counties with stronger 850mb flow arriving from the southwest with the jet. 50kt+ winds as low as 2-3kft will not take much to get pulled to the surface by the convective line. Large hail also remains a concern with the steep lapse rates in the mid levels and modest instability within the hail growth zone.

The trailing line of convection from near KSPI back into northeast Missouri is setting up along the spine of the low level jet and will pivot into the western part of the forecast area by 09-10Z and spread east through the first half of the morning. The orientation of the convection introduces more concern for localized flash flooding in addition to the inherent severe weather risk that will impact the forecast area through about 15Z. Any training of convection will have the potential to produce in excess of 2 inches rain quickly this morning. Instability will remain sufficient through the morning but will drop back somewhat from earlier levels with the overall wind profile transitioning to more unidirectional as storms move east across the forecast area. With low level jet winds strengthening...damaging winds will remain the prevalent severe weather threat with large hail and isolated tornadoes becoming secondary concerns. SRH values through the lowest 1-2km remain very strong however and support at least an isolated tornado risk with more intense cells or with any bookend.

Separate from convective winds...an increasing signal with stronger gradient flow develops in the wake of the morning storms but ahead of the frontal boundary set to pass through later today. Growing more confident in the potential for non-convective gusts to peak at 45 to 50mph at times later this morning into the afternoon focused especially across the southeast half of the forecast area. Have issued a Wind Advisory to highlight this threat from 12Z through 21Z.

This Afternoon through Tonight

Showers will linger in the wake of the morning convection with the possibility of a brief lull in rain near midday. By early afternoon the frontal boundary should be bisecting the forecast area with the potential for renewed convective development along the boundary as instability increases and strong shear and SRH through the near surface layer lingers. Hodographs through the lowest 1-2km are more straight as opposed to curved and less favorable for rotating storms. Damaging wind gusts will be the main threat focused across the southeast half of the forecast area for a few hours this afternoon before clearing the region by 21Z. Additional rainfall should be a half inch or less this afternoon with rain ending over far southeastern counties around sunset.

The stronger gradient wind flow and the impact to temperatures across the frontal boundary will become bigger factor throughout the afternoon. While temps from the mid 60s to lower 70s will remain prevalent through daybreak...temperatures will fall steadily from northwest to southeast into the afternoon as the front passes. By late today...expect a 20 to 25 degree difference from the northern Wabash Valley to southeast Indiana. Must of the forecast area will fall into the 40s prior to sunset eventually tumbling into the upper 20s and lower 30s by daybreak Thursday as skies clear and high pressure expands into the region.

LONG TERM (Thursday through Tuesday)

Issued at 259 AM EDT Wed Mar 11 2026

Noticeably cooler trend under quasi-persistent H500 troughiness will return central Indiana to a seasonable mix...of occasionally mild and brief cold conditions. Downstream strong upper ridging over northwest Atlantic will combine will steady flow of short waves amid kicking west-northwest flow over the northern Rockies...to promote more rounds of stronger cyclogenesis...first over the Upper Midwest Thursday night and Friday...and then early next week from the central Plains to the eastern Great Lakes. Late-winter arctic air will most likely follow the early-week system, plunging subfreezing readings into much of the northeastern CONUS.

This will all translate to a bright yet cool Thursday struggling to rebound to 50F amid moderate CAA breezes...a windy late Thursday night and Friday from the passing northern storm...and a typical March day Saturday with lighter breezes bringing mainly low to mid- 50s under considerable cloudiness. Conditions to turn more active Sunday as next system deepens while crossing the Midwest...bringing stronger southerly gusts, mid-April temperatures, and numerous showers/few TRWs. A 40-degree temperature drop is possible going into the next workweek, bringing the region's first hard freeze in two weeks and probably a short burst of mixed precip or wet snow. Quick arctic air mass to end the long term will likely have one daytime only peaking near the freezing mark and one overnight into the teens. Additional chances of low-impact snow towards the mid- week when a weaker clipper system should start transition back to near normal readings.

AVIATION (18Z TAF Issuance)

Issued at 113 PM EDT Wed Mar 11 2026

Impacts:

- MVFR conditions much of this afternoon and into the evening.

- Showers and isolated Thunderstorms will be possible this this afternoon and evening.

- A return to VFR will be expected late tonight.

Discussion:

Radar shows areas of showers and thunderstorms across central Indiana returning along a cold front that is crossing the state. Strongest storms will be across southern Indiana, within the warm sector ahead of the front where dew points remain in the 60s. VFR cigs were present ahead of the front, while cold air advection in the wake of the system was allowing for low MVFR cigs along with scattered rain showers.

The front will sag southeast across Central Indiana this afternoon. This will continue to allow periodic showers and isolated thunderstorms to continue, as winds shift to the northwest. A moderate pressure gradient across the area along with strong winds aloft will continue to allow for gusty winds through the afternoon and into the evening.

High pressure will build across the area late tonight, leading to winds subsiding and skies becoming VFR.

IND WATCHES/WARNINGS/ADVISORIES

Wind Advisory until 5 PM EDT this afternoon for INZ039>042- 045>049-051>057-060>065-067>072.