textproduct: Indianapolis

KEY MESSAGES

- Showers and thunderstorms expected tonight with a threat for heavy rainfall and isolated large hail in southern portions of central Indiana.

- Flooding threat on area rivers will continue across southern Indiana after multiple rounds of heavy rainfall.

- Below normal temps for late this week into the weekend.

- Frost possible this weekend.

- Slow warm up with rain chances returning early next week.

FORECAST UPDATE

Issued at 1020 PM EDT Tue Apr 28 2026

Other than a few isolated showers in the far south, this evening has been dry across central Indiana. However, regional radar shows showers and thunderstorms across southern Illinois moving east toward the southern forecast area. Temperatures were in the lower 50s north to lower 60s south under mostly cloudy to cloudy skies.

Forcing will continue to increase and move into central Indiana tonight with an upper wave as well as surface low pressure to the south of the area. This will bring rain to much of the area, so kept high PoPs.

Locally heavy rain remains a threat tonight, especially south closer to the higher moisture content. Guidance continues to show the potential for a band of heavier rain setting up somewhere in or near the southern half of the area. Will continue to mention a threat of locally heavy rainfall and flooding overnight.

Some elevated instability will move in overnight, mainly south. It appears that the greatest threat for severe hail will remain south of central Indiana based on latest trends, but will continue to monitor closely.

Forecast temperatures look reasonable given expected conditions.

DISCUSSION (This evening through Tuesday)

Issued at 314 PM EDT Tue Apr 28 2026

Tonight....

Scattered to numerous TS over Missouri are associated with a broad WAA pattern ahead of a shortwave trough moving through the central Plains. This activity will continue to be supported by elevated instability (MUCAPE from 1000-2000 J/KG) while shifting eastward into southern half of IL into the evening hours. Recent RAP mesoanalysis shows the northward extent of the moderate elevated instability is further north that most of the CAM/12Z HREF guidance suggested. Therefore, unlike the bulk of guidance which shows less than 500 J/KG of MUCAPE across the far south parts of the central IN, expecting with a feed of 8-8.5 C /KM mid level lapse rates coupled with an increasing low level jet expected to form in the wake of the Ozarks this evening, MUCAPE values will be roughly double these values running from 500 J/KG near I-70 to near 1000 J/KG down near the US 50 corridor. Also as a result of the increased instability, the forecast has gone more bullish with TS chances across the southern portions of the forecast area as well as including the mention of locally heavy rainfall. SPC Day 1 outlook maintains a marginal risk for severe hail in the far southern portions of the forecast area, but believe that the severe hail threat is 50-100 mi further north accounting for the greater instability.

Regarding the heavy rainfall threat, soil moisture values across the southern portion of the forecast area are running between 50 and 70 percent saturated. Thus it will not take much rain for flash flooding. OHRFC flash flood guidance has most of this area in 1.5 to 2 inch/6hr and 1.5 inch/3 hr. A Flash Flood watch was considered, but given some uncertainty in reaching at least 1.25-1.5 inch QPF overnight, opted to not issue and to let later shifts reassess for the potential for more cell training and higher amounts.

Wednesday through Friday...

An unsettled and cool pattern will set in for the remainder of the work week as broad NW flow and several weak mid level perturbations move across the region around a longwave trough centered over eastern Canada/CONUS. Just ahead and in the wake of the first shortwave on Wednesday, CAA and wrap around scattered light showers are expected in eastern zones during the afternoon. Skies should be mostly clear Thursday. Low PoPs were added for Thursday Night to account for the consensus timing of another shortwave which will move SE across the region pinwheeling around the closed low centered south of Hudson Bay.

Saturday/Sunday...

As the closed low/long wave trough move gradually east, surface high pressure will build southward from the northern Plains. The high pressure ridge axis will be just to the northwest of the forecast area on Saturday morning, with the potential for some low clouds and winds remaining 5-10 mph. By Sunday morning, the surface high ridge axis shifts to nearly over central Indiana per the Euro, but slightly south of the central Indiana per the GFS. Either way, temps are expected to be well below normal this weekend with generally light winds and clear skies. A dry airmass with dewpoints near 32F will favor the potential for patchy and possibly more widespread frost, especially in outlying areas both mornings. Highs near 60F (about 10 deg below normal) are expected for afternoon highs.

Early next week...

Guidance is mixed on the timing of additional shortwave energy moving out of Canada. In the wake of high pressure, expect at least a slight warmup to near normal temperatures Monday and Tuesday. NBM has low PoPs for Monday into Tuesday based on smoothing out the timing of weak shortwaves in the W-NW flow aloft. Given a frontal intrusion in the Gulf this weekend, moisture return will be meager and any precipitation should be primarily showers with isolated sub- severe TS possible.

AVIATION (06Z TAF Issuance)

Issued at 1215 AM EDT Wed Apr 29 2026

Impacts:

- Isolated to scattered TS tonight at all but KLAF. - MVFR ceilings return overnight at all sites with IFR conditions expected at KHUF/KBMG. - Gusty winds tomorrow out of the NW, peak gusts around 25kt

Discussion:

Ceilings will gradually lower through the VFR category through 06Z or so, then MVFR and some IFR conditions will develop from the southwest. IFR is expected by 09Z at KBMG and likely at KHUF. Cannot rule IFR out at KIND but am not confident enough to include. Ceilings will gradually improve Wednesday morning, reaching VFR by around 18Z.

Showers and some thunderstorms will push in from the southwest late this evening. Showers will then continue at times into Wednesday morning. Some uncertainty exists on thunderstorm coverage, especially at KIND.

IND WATCHES/WARNINGS/ADVISORIES

None.