textproduct: Indianapolis

KEY MESSAGES

- Light rain chances tonight through Sunday with minimal accumulations

- Unseasonably warm conditions Monday and Tuesday, reaching the low 70s

- Active weather with thunderstorms and heavy rain Tuesday night into Wednesday

DISCUSSION (This evening through Saturday)

Issued at 124 PM EDT Sat Oct 31 2026

Overview.

A quiet start to the week will gradually transition to active and much warmer weather by midweek before colder, drier air returns next weekend. A weak disturbance brings a slight chance of light rain tonight and Sunday, though most areas will see very little measurable precipitation. Cloud cover will persist into early next week as winds turn southerly, driving temperatures well above normal into the low 70s by Tuesday. A strong low pressure system and accompanying cold front will bring widespread rain, gusty winds, and thunderstorms late Tuesday night into Wednesday. High pressure builds in behind the front for Thursday through Saturday, bringing dry conditions and seasonal temperatures back to central Indiana.

Tonight Through Sunday.

A broad 500mb shortwave ridge continues to shift into the eastern Ohio Valley as a low-amplitude trough lifts northeast out of the lower Mississippi Valley. Ahead of this weak impulse, 850mb warm air advection and isentropic lift will continue to transport mid-level moisture across central Indiana. Model soundings and the 12Z HREF mean indicate a substantial dry layer below 700mb, characterized by surface dewpoint depressions in excess of 15 degrees. HREF component members consistently demonstrate that initial radar echoes will struggle against this sub- cloud dry air, resulting predominantly in virga during the evening hours. As top-down saturation gradually occurs overnight, dew point depressions will drop sufficiently to support scattered sprinkles and light rain showers, primarily across the southern and western portions of the CWA. Measurable QPF will remain minimal, with ensemble means generally showing less than 0.05 inches through 12Z Sunday.

Extensive multi-layered cloud cover and light southeasterly winds around 5 to 10 mph will limit diurnal cooling overnight, with low temperatures holding in the mid 50s. On Sunday, the weak mid-level vort max dampens as it traverses southern Indiana. Weak boundary- layer convergence along an inverted surface trough will sustain isolated to widely scattered light rain showers through early afternoon, primarily east of the I-65 corridor. Weak subsidence aloft behind the wave should allow precipitation to diminish from west to east late Sunday afternoon, though abundant low-level moisture trapped beneath a strengthening subsidence inversion will keep skies mostly cloudy. Sunday high temperatures will remain muted by cloud cover, peaking in the mid to upper 60s.

Monday Through Saturday.

The synoptic pattern becomes amplified and highly progressive early in the week. A deep, positively tilted longwave trough establishes over the western CONUS on Monday, inducing strong downstream height rises across the eastern states and setting up deep southwesterly flow through the central CONUS. A surface warm front will lift northward across central Indiana on Monday, placing the forecast area securely in the warm sector. The pressure gradient will tighten in response to cyclogenesis over the central Plains, establishing a robust 40 kt low-level jet that advects an anomalously moist airmass from the Gulf. WAA will support 850mb temperatures rising to +14C to +16C, supporting surface highs reaching the lower 70s on Tuesday, roughly 10 to 15 degrees above seasonal normals.

Active and potentially severe weather remains focused during the Tuesday night into Wednesday timeframe as the primary synoptic cyclone deepens over the upper Midwest and drives a potent cold front eastward. Deep convective dynamics will be heavily supported by upper-level divergence within the right-entrance region of an intense 130 kt 250mb jet streak, coupled with strong differential PVA ahead of the trough axis. 500mb southwesterly flow is expected to be around 60 to 75 kt and an 850mb jet intensifying to 50 to 55 kt with the system. This wind field generates 0-6 km bulk shear values of 50 to 65 kt and 0-1 km storm-relative helicity values between 150 and 250 m2/s2, which are more than sufficient to organize convection.

The primary limiting factor regarding severe convective hazards will be the thermodynamic profile, characterizing this setup as a classic cool-season HSLC regime. Deterministic GFS and ECMWF runs along with GEFS and EPS ensembles continue to show poor mid-level lapse rates around 5.5 to 6.0 C/km. Surface dewpoints in the low 60s will provide modest boundary-layer destabilization, but nocturnal timing will temper surface heating, holding MLCAPE generally within the 300 to 750 J/kg range. Given the strong linear forcing along the advancing pre-frontal trough and cold front, convection will favor upscale growth into a linear system. The main convective hazard will be damaging straight-line wind gusts generated by momentum transfer within convective downdrafts tapping the 50 kt ambient flow at 850mb. An isolated tornado risk cannot be ruled out within bowing segments or line breaks where low-level shear vectors orient perpendicular to line segments. Deep moisture and flow parallel to the frontal boundary could support localized training and minor hydrological issues, though rapid frontal translation should cap total rainfall between 1.00 and 1.75 inches.

The cold front is expected to clear eastern Indiana by midday Wednesday, bringing an end to precipitation and initiating strong cold air advection on brisk northwest winds. Broad Canadian surface high pressure will build southeastward into the Ohio Valley for Thursday through Saturday. Mid-level flow transitions to a dry, low- amplitude northwest regime, promoting widespread subsidence and clear to partly cloudy skies. Temperatures will return to seasonal late-autumn levels, with 850mb temperatures falling below 0C. Daytime highs will fall back into the upper 50s to lower 60s on Thursday, and further into the low to mid 50s by Friday and Saturday. Nighttime lows will settle into the upper 30s to lower 40s across central Indiana through the end of the period.

AVIATION (18Z TAF Issuance)

Issued at 124 PM EDT Sat Oct 31 2026

Impacts:

- None

Discussion:

VFR conditions expected through the TAF period with only minimal chances for brief vsby restrictions towards BMG after 12Z Sunday due to scattered showers.

Mid and high clouds are expected to continue to advect across central Indiana through tomorrow with ceilings dropping to around 050 after 06Z. There may be a few sprinkles during the overnight with better chances for rain after 12Z, especially towards BMG.

Winds will generally out of the east at 5 to 10 kt through the TAF period.

IND WATCHES/WARNINGS/ADVISORIES

None.