textproduct: Indianapolis

KEY MESSAGES

- Showers and thunderstorms expected this morning with minor flooding possible

- 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, with frost possible Saturday morning.

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

DISCUSSION (Today through Tuesday)

Issued at 232 AM EDT Wed Apr 29 2026

Today and Tonight....

A weak surface low is passing to the south this morning ahead of a secondary shortwave. This has led to numerous showers and thunderstorms, of which will push into southern Indiana, mainly forced by marginal deformation within the 850-700mb low. Broad isentropic lift ahead of the wave is also leading to light showers over central IL, of which should continue into central Indiana this morning as well. The greater forcing within the deformation to the south is allowing for some elevated convection and lightning creation. This should remain confined to areas south of the I-70 corridor, with heavier rain rates in the area as well. Due to the more confined area of forcing, greater QPF is expected, and with prior rainfall of 3-5" across this same area yesterday, minor flooding is possible within flood prone areas.

The wave should slowly exit throughout the day with isentropic induced showers leaving the area early this afternoon. NW flow will arrive behind this wave, with much cooler air aloft. Moisture will be limited but pockets of shallow convective showers may develop during the afternoon with gusty surface winds as the PBL becomes well mixed. Although not hazardous a few instances of graupel within these convective showers cannot be ruled out.

The cold air advection within this NW flow will slowly build surface pressure to end the work week, with clearing skies by tonight. The resulting airmass will be only slightly cooler than normal, but with high pressure and clear skies, efficient diurnal cooling tonight could allow for a few areas in the Wabash Valley to fall below 40 degrees tonight into tomorrow morning. While widespread frost is not expected, patchy frost cannot be ruled out on elevated surfaces over this same area.

Thursday through Friday...

While entrenched within shortwave ridging and surface high pressure exiting to the east, skies should be mostly clear throughout the daytime hours on 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. Strong zonal flow aloft on Friday will likely lead to quiet conditions with frequent cirrus cloud cover.

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 (12Z TAF Issuance)

Issued at 653 AM EDT Wed Apr 29 2026

Impacts:

- Showers with MVFR VIS through 14Z at KIND and KBMG - Isolated showers this afternoon, with a low chance of thunder at KIND and KLAF - Gusty winds this afternoon out of the NW, peak gusts around 25kt

Discussion:

Showers ahead of a departing wave will continue into the mid morning at KIND and until late morning at KBMG. At these sites, IFR ceilings may remain initially before improving throughout the morning. All TAF sites are expected to be VFR by early this afternoon. Isolated showers are expected at KIND this afternoon (less than 30% chance at KLAF). Cannot rule out lightning completely, but chances were too low to include at this time.

Winds will become gusty this afternoon, with routine gusts between 18-23kt. Gusts within showers may be a bit higher. Winds will decrease overnight to less than 10kt. A scattered to broken deck around 4000ft is expected to accompany these showers before becoming mostly clear tonight.

IND WATCHES/WARNINGS/ADVISORIES

None.