textproduct: Indianapolis

KEY MESSAGES

- Wind gusts of 30 to 40 MPH at times again Thursday.

- Wet pattern through the week and into the weekend, with multiple rounds of showers and storms expected, which may produce renewed flooding along area waterways

- A few strong to severe storms and locally heavy rainfall are possible mainly northern portions of central Indiana tonight.

- Potential for additional heavy rainfall and severe weather for late Thursday and again late Saturday.

- Drier and cooler weather for early next week.

FORECAST UPDATE

Issued at 948 PM EDT Tue Mar 31 2026

Some showers and thunderstorms have finally entered portions of the northwest forecast area this evening. These are along a cold front, with convection now stretching southwest into central Illinois. Temperatures in northwest Indiana behind the front were in the mid 40s, but ahead of the front readings were in the lower and middle 70s.

With convergence continuing along the front, along with some instability (MUCAPEs less than 1000 j/kg), expect showers and thunderstorms to become more widespread into the overnight. Current trends indicate that the northern forecast area will have the most coverage, so kept PoPs high there. Did tighten the gradient from the high PoPs north to the chance PoPs south based on latest trends seen in guidance. (Did not cut as much as the HRRR would suggest, as its coverage looks underdone based on what's on radar now).

With the instability and weak shear, a strong to potentially severe storm cannot be ruled out into the early overnight. Have seen gusts near 50mph in central Illinois with the convection this evening but nothing severe. As instability weakens overnight, odds of strong convection will decrease.

Locally heavy rain from storms remains a threat, mainly across the northern forecast area where multiple rounds of convection are possible.

Temperatures will get into the 40s in the northwest behind the front, with readings remaining in the 60s south ahead of it.

MESOSCALE UPDATE

Issued at 806 PM EDT Tue Mar 31 2026

Central Indiana remains convection free near 00Z this evening, with convection across northern Indiana and across portions of Illinois.

Some weak CIN remains across the local area, with MLCAPE below 1000 J/kg. Better shear remains across northern Indiana, where convection there is being assisted by an upper wave.

Convection to the north and northwest of central Indiana is firing along a cold front, which with assistance from cold advection from Lake Michigan has pushed south of KRZL. At least scattered convection should continue to fire along the front thanks to deeper convergence and the available instability.

This convection hasn't become severe, and with the better shear off to the east and north, feel that any severe threat across the northern forecast area in the next couple of hours would be isolated.

SHORT TERM (This evening through Wednesday)

Issued at 329 PM EDT Tue Mar 31 2026

Rest of this afternoon...

Subtle shortwave trough will continue to push east through the lower Great Lakes. Ample elevated instability (MUCAPE around 1000 j/kg) and limited instability will support a threat for scattered thunderstorms with small hail, gusty winds up to 45 mph and locally heavy rain for the next 1-3 hrs before weakening and ending from the west by 22Z.

Tonight...

Thunderstorms have begun to develop along a line from the western Chicago Suburbs back towards the Quad Cities. This activity is forming in a region of deep moisture convergence ahead of the main frontal boundary. Expected storm motions and current location agree with bulk of CAM guidance which moves this activity into far NW portions of central Indiana around 00Z. Similar to this mornings activity, threat will initially be large hail thanks to steep mid level lapse rates up to 7.5 C/KM. Elevated TS activity that moved through NW portions of the forecast area in the last 1-2 hrs has stabilized the BL. However, sufficient heating should redevelop before 00Z that near surface based parcels will support an additional threat for damaging winds. Activity will also be working with around 1.3 inch PWAT, which combined with slow storm motions will lead to threat for locally heavy rainfall. The threat for severe down to I-70 per recent SPC day 1 outlooks seems a little too far south given the slow storm motions and increasing cinh with southward extent. However the WPC day 1 marginal location looks reasonable. As the cold front accelerates southward later tonight, aided by CAA of Lk. Michigan, expect the greatest the for heavy rain to gradually shift south towards I-70 by 12Z Wednesday.

Wednesday...

Given strong convective overturning and weakening mid level lapse rates owing to building heights and latent heat processes, thunderstorm activity will continue to weaken and diminish in coverage during the morning. However, strong deep convectively enhanced frontal convergence aided by 30-40 kt 850mb jet will support the threat for multiple rounds of heavy showers along the frontal boundary during the day. Uncertainty exists on the exact QPF amounts, so decided to not hoist a Flood Watch, but over 1 inch of QPF is possible between 12-00Z. Expecting the frontal boundary to push much further south than NBM guidance and thus have undercut highs by 1-2 categories, remaining in the 40s/50s along and north of I-70.

Wednesday night...

Frontal boundary will lift northward as a warm front as strong pressure falls develop associated with another shortwave trough digging southward through the rockies and surface low pressure intensifying over the high plains. Showers and isolated TS chances will end quickly from the south early in the period as the front moves north of the CWA by 06Z. In fact Wednesday's high temps for most areas north of I-70 will occur just before 04Z.

Thursday and Thursday night...

As the next shortwave kicks eastward into the plains into the western Great Lakes, an associated frontal zone will push eastward to near the upper MS river by Thursday afternoon. Early morning TS over the Ozarks may move far enough east to aid in a convective outflow boundary ahead of the primary frontal forcing to support renewed convection along this boundary by afternoon just west of central IN. With little to no mid level height falls, soundings indicate substantial inversion centered around 500 mb robbing a deeper CAPE profile. Thus the slight risk has a lot of conditional nature to it, with many negatives limiting the threat at the moment. NBM Pops were lowered some, but possibly not enough given the limited deep forcing and marginal instability.

LONG TERM (Wednesday night through Tuesday)

Issued at 329 PM EDT Tue Mar 31 2026

Unseasonably warm and anomalously humid pattern to continue into the late week amid continued chances of rain/thunder..before mid-weekend transition to dry and much cooler conditions early next week. Indiana's position, Friday and into Saturday, in the subtropical warm sector south of a rather quick zonal mid-level flow near the CONUS-Canada border...will provide a quasi-continuous ribbon of anomalously high precipitable water off the Gulf, separated by perhaps a shorter period of drier mid-levels between passing. rounds of forcing. Steady S/SSW surface flow will hold 55-65F dewpoints over the CWA, promoting high-POPs of low-QPF around the Friday timeframe. Overall breezy conditions will likely include one more windy day Thursday where gusts to at least 25-35 mph will be possible.

Final period of steadier rainfall is expected to precede a regime- changing cold front expected to cross Indiana around the late Saturday-Saturday night timeframe. Widespread moderate rainfall and isolated to scattered thunder would be the most likely solution, with potential for an additional 1.00-2.00 inches of rainfall under heavier downpours/storms...as the boundary takes a slower passage across the region. This final round of rain may be the one to take a few local creeks and river points from Action Stage into Minor Flooding, or at least prolong ponding of low-lying areas into early next week.

A distinct transition to below normal temperatures will follow into Sunday, with rain-free conditions and dewpoints falling to around 30F as seasonably strong surface high pressure builds into the Great Lakes/Midwest into Monday. Current NBM timing would only allow maximums 10 degrees below normal Sunday...with subsequent clearing and diminishing winds promoting frost late Sunday night. Any moderation into the mid-week to be modest and towards near normal conditions. The normal max/min at Indianapolis through the long term is 60/40.

AVIATION (00Z TAF Issuance)

Issued at 706 PM EDT Tue Mar 31 2026

Impacts:

- Convection may reach KLAF 01-02Z with weaker convection expected at KIND by 04-05Z - Showers/light rain with perhaps embedded thunder after 08Z . Wind shift to the north will impact KLAF by 03Z with later sites after 06Z - Widespread MVFR conditions developing overnight with IFR in the north

Discussion:

Convection across IL could reach KLAF by 01-02Z but it will take a while to reach the other sites. Convection is expected to weaken during the later evening into the overnight. More widespread rain with perhaps embedded thunder will impact most sites after 08Z, with uncertainty highest at KBMG.

Winds will shift as a cold front moves south through the area tonight. There remains some uncertainty on the timing of the wind shift at the southern sites as a surface wave may move along the front. MVFR and some IFR will develop overnight and persist Wednesday.

IND WATCHES/WARNINGS/ADVISORIES

None.