textproduct: Indianapolis

KEY MESSAGES

- Near daily rain and occasional thunderstorm chances this week into early next, with an additional 2 to 4 inches of rainfall likely through Saturday, will produce widespread minor to moderate flooding across central Indiana creeks and rivers.

- A few strong to severe storms possible into tonight generally south of I-70.

- Much warmer late week into next week, with near record warmth likely Friday and potentially early next week as well.

FORECAST UPDATE

Issued at 850 PM EST Wed Mar 4 2026

Convection that was aided by an MCV will continue to diminish and shift eastward and out of central Indiana by 02Z. Recent cell training and heavy rainfall (amounts around 1.5 in/hr) has lead to localized flood/flash flood threat in SE portions of central Indiana that will last a few hours beyond the end of the rainfall.

In the wake of the MCV, ACARs soundings show subsidence layers centered between 650 and 800 mb which have become well established over western Indiana back towards St. Louis. Although a few convective showers have recently developed along the IN/IL border, these are not expected to intensify to thunderstorms owing to the 50- 100 j/kg of mucinh shown on recent mesoanalysis and a result of the subsident layers. Patchy fog has recently developed over far western IN in this region of subsidence aloft. Visibilities have not yet fallen to less than 1/2 mile, but have done so in IL recently. We will continue to monitor trends and may issue a Dense Fog Advisory before 10 PM if dense fog conditions develop and increase.

Convection over MO which has developed in the last few hours will continue to increase in coverage as it moves towards central Indiana owing to increasing deep layer moisture convergence along the leading edge of intensifying 850 mb jet, as well as DCVA ahead of plains shortwave trough. A renewed threat for heavy rainfall/minor flooding will develop after 05Z as high PWATS (1.2 to 1.3 inch per soundings) combine with convection focusing along and just north of stationary front over southern portions of central Indiana. The threat for flash flooding may increase yet again late tonight, if sustained cell training can become focused over the same areas that received heavy rainfall this evening, namely along the U.S 50 corridor.

SHORT TERM (This evening through Thursday)

Issued at 323 PM EST Wed Mar 4 2026

Tonight through Thursday....

Surface frontal boundary extends along the Ohio River valley of southern Indiana just south of central Indiana. A weak-moderately unstable airmass exists across the region, with elevated MUCAPE values on the order of 500-1000 J/KG north of the front. A well defined MCV in the vicinity of STL has supported recent convective line development over the MS valley of Southern IL. This activity is expected to be maintained and strengthened as it rides along and just north of the surface frontal boundary into southern portions of central Indiana late this afternoon/early evening. With 30-40 kts of deep layer shear, updraft rotation will be sufficient for organized multicells and weak supercell structures. Mid level lapse rates are not overly steep (6.5-7 C/km) but sufficient to enhance the potential for marginally severe hail production. There is an outside chance of an isolated damaging wind gusts/tornado along the frontal boundary in far southern counties of central Indiana if sufficient surface based buoyancy can be realized.

An increasing 850mb jet impinging on stationary front over the central Plains/Ozarks along with an approaching mid level shortwave trough will lead to regeneration and increase in a large area of convection west of central Indiana later this evening moving into central Indiana overnight.

Recent rainfall of 2-4 inches has lead to fairly saturated grounds and rivers to rise into minor to moderate flooding generally along and south of I-70. Expectation is for additional 1-3 inches of rainfall to occur with these areas as multiple rounds of convection move through Thursday morning. Therefore a Flood watch has been issued through noon Thursday with the potential for minor low lying flooding and continued increase in river/creek flooding.

The mid level shortwave is expected to pass through central Indiana tomorrow afternoon. There is a chance for scattered TS development prior to frontal/shortwave trough passage.

Thursday Night and Friday...

The frontal boundary is expected to become stationary along the Ohio River valley Thursday night before lifting back northward as a warm front on Friday. Areas of fog and or showers will be possible late Thursday night early Friday prior to the warm frontal passage. However, TS coverage appears negligible with building mid level heights in the wake of the shortwave trough. As 850mb temps rise to +13-14C Friday with moderate SW low level flow aiding in mixing, expect temps to rise well into the 70s, with current record temps in jeopardy (Indy's record is 75 in 1973).

Friday night...

A fairly strong cold front will push east through the plains Friday evening before reaching the MS valley by 12Z Saturday. A fairly long and fast line of thunderstorms is expected ahead of this front, possible reaching the border of Indiana by 12Z Saturday. A marginal risk for severe weather seems more than appropriate considering the very warm/moist airmass and strong deep layer shear vectors in place.

LONG TERM (Thursday night through Wednesday)

Issued at 323 PM EST Wed Mar 4 2026

The wet pattern will dry out slightly on Saturday through Wednesday.

Saturday...

Models suggest a moderate trough over the the plains on Saturday morning within the upper levels. This feature will progress toward Indiana through the day. Within the lower levels, Indiana will start the day within the warm sector with a cold front to west poised to push across the state. Showers and Storm chances will be needed given the expected passage of the cold front as ample moisture and forcing will be available. Forecast soundings show pwats over 1 inch, thus confidence is high for rain.

Saturday Night through Monday...

Zonal flow aloft is expected during this time in the wake of the departed upper trough on Saturday. The departed upper trough will lead to subsidence building across the area on Sunday and into Monday. Model response to this with a elongated area of high pressure suggested to build from the southern plains. This system will bring dry and mild weather through this period. Forecast soundings through the period show a dry column. Southwest flow developing by Monday and Tuesday with allow for a warmer air to continue to arrive resulting in mild and warm spring like temperatures.

Tuesday and Wednesday...

Another cold front along with an area of low pressure is expected to settle across the Central Indiana on Tuesday afternoon through Wednesday. An upper trough is will be settling over the Rockies at that time, and this will eject some forcing dynamics toward Indiana as the front is present. Thus given these signals, pops will be needed, with slightly cooler temperatures.

AVIATION (00Z TAF Issuance)

Issued at 649 PM EST Wed Mar 4 2026

Impacts:

- Widespread IFR-LIFR ceilings through Thursday morning.

- Widespread IFR visibilities through Thursday morning.

- Widespread showers with thunderstorms ending from west this evening with more development late tonight.

- Additional scattered thunderstorms possible Thursday afternoon for KBMG/KIND.

Discussion:

Thunderstorm threat has ended for the time being at KHUF AND KLAF. Thunderstorms will end within the hours at KIND/KBMG. Widespread IFR/LIFR ceilings and IFR vsby will continue overnight, although there maybe a brief window for 1-2 hrs of VFR in the immediate wake of the showers/TS this evening.

Another round of showers and thunderstorms currently developing over the Ozarks will move back into the TAF sites between 05-08Z, with little to no impact expected for the cargo ops at KIND. Shower and thunderstorm activity will diminish between 10-15Z Thursday morning. A weak front will move across Indiana during the afternoon hours with a chance for scattered TS to effect KIND/KBMG during the afternoon hours. In additional ceilings are expected to improve to MVFR during the early afternoon hours.

IND WATCHES/WARNINGS/ADVISORIES

Flood Watch through Thursday morning for INZ043>049-051>057- 060>065-067>072.