textproduct: Indianapolis

KEY MESSAGES

- Above normal temperatures through the weekend, with near record highs on Sunday

- Showers and thunderstorms possible on Sunday, a few strong to severe storms cannot be ruled out.

- Mostly dry and warmer than average conditions expected next week.

SHORT TERM (Today and tonight)

Issued at 312 AM EDT Sat Mar 21 2026

A cold front passed through yesterday evening with brisk northerly winds. These winds are already diminishing as surface high pressure moves in overhead. By morning, high pressure will already be passing to our east with winds becoming southerly.

A surface low, embedded within northwesterly flow aloft, approaches from the northwest this afternoon. An increasing MSLP gradient ahead of this feature should promote increasing winds and warm air advection through the day today.

High cloud cover associated with a subtle vort max aloft may linger into the morning hours, but should diminish with time. Mainly clear skies are anticipated during the afternoon hours. This should allow for efficient diurnal mixing. Combined with the warm air advection, temperatures likely trend higher than guidance similar to previous days. Our forecast will reflect this, with highs in the mid to upper 70s for the majority of our CWA.

A potent low-level jet develops overnight as the aforementioned low makes its approach. A persistent breeze at the surface likely limits the effectiveness of radiational cooling overnight. With continued warm air advection, low temperatures are expected to be quite warm with readings falling to near 60 for most.

LONG TERM (Sunday through Friday)

Issued at 312 AM EDT Sat Mar 21 2026

Our attention continues to be focused on Sunday with the surface low mentioned in the short term. This system becomes rather disorganized as it moves southeastward, elongating into a broad surface trough extending from Texas to Pennsylvania. Of particular interest is the system's cold front which may be quite strong.

SUNDAY TEMPERATURES

Focusing on the cold front first, we'll take a look at expected temperatures on Sunday. The air mass ahead of the front is warm with 850mb temps near 18-20 degrees. Assuming ideal adiabatic mixing, this would place high temperatures into the 80s. However, the high temperature forecast tomorrow is tricky due to the approaching front. Guidance has trended a bit faster with the front arriving across our northern counties as early as 21z.

This would limit how long these locations have to warm up before the front arrives. In the scenario of a faster front, temperatures failing to climb out of the 60s is possible. The greatest likelihood of high temperatures below 70 are from Lafayette to Kokomo and points northwestward. Further south, a rapid warm up under mostly sunny skies is expected. Diurnal mixing may be very efficient, with surface temperatures reaching their full potential. As such, highs in the 80s are likely. A few locations may even climb into the mid to upper 80s, especially further south and west.

SUNDAY THUNDERSTORM POTENTIAL

Next, we will take a look at the potential for showers and thunderstorms with the approaching front. Since guidance has trended towards a slightly faster front, our threat for storms has shifted southward. The threat remains conditional, as forcing aloft is subtle at best...confined to slightly favorable jet dynamics. At the surface, the strong cold front will act at the primary forcing mechanism. However, this brings about its own problem as the mean flow is east-southeasterly and the front is moving due south. Given the strength of the front, it may quickly undercut developing updrafts and prevent them from reaching maturity.

However, given tall and wide CAPE profiles, this may not be a huge issue for storm potential. As long as a few updrafts can sustain, they may simply become elevated and continue to mature within the unstable air above the shallow surface front. Storms that do form would have ample shear to work with, and so severe weather would be possible even with elevated storms. Shear profiles show long curved hodographs. However, if storms are not surface based then the effective shear profile becomes rather straight. As such, large to very large hail would be the primary hazard. Strong wind gusts are possible as well, since downdrafts may still be able to penetrate the shallow surface cold layer via momentum. The most probable timing would be late afternoon into the early evening hours.

Gusty gradient winds between 25-35 mph are expected behind the front.

NEXT WEEK

Anomalous ridging out west continues to dominate the large-scale pattern. Our weather is therefore expected to be similar to recent days with broad northwesterly flow aloft and southerly flow at the surface. Overall, warmer-than-average temperatures and dry conditions are favored. Occasional systems embedded within the northwesterly flow may periodically drag a cold front across the region leading to brief cool-downs. Showers and thunderstorms may accompany these fronts but that depends on the quality of moisture return prior.

AVIATION (06Z TAF Issuance)

Issued at 134 AM EDT Sat Mar 21 2026

Impacts:

- Generally light winds veering from NNE to ESE by 14Z Saturday - Winds continuing to veer through midday/afternoon hours, to SSW, while increasing slightly

Discussion:

VFR conditions to prevail through Saturday night over central Indiana terminals. TAF period starts with weak cool frontal zone stretched over the region...which overall zonal pattern will quickly return northward during morning and midday hours. Mainly dry column and better Gulf moisture staying south of the Ohio River will promote mainly high cloud into late Saturday night.

Generally lighter winds will veer from north-northeast to easterly by 13Z and southerly by 18Z...with 190-230 degrees prevailing Saturday evening and overnight. Winds sustained around 5-10KT on Saturday after 14Z.

IND WATCHES/WARNINGS/ADVISORIES

None.