textproduct: Indianapolis

KEY MESSAGES

- Unseasonably warm temperatures in the 70s to near 80 expected through Saturday.

- Slight chances of rain late Thursday northern sections.

- Higher chances of rain Saturday Night into Sunday.

- Mild and wetter pattern likely next week.

DISCUSSION (This evening through Wednesday)

Issued at 309 PM EDT Wed Oct 28 2026

Tonight through Thursday night...

A broad area of surface high pressure extending from New England into the Srn Appalachians will slowly give way to a low pressure area and cold front moving from the northern Plains into the western Great Lakes region. Winds will remain light southerly overnight with lows in the upper 40s to lower 50s area wide. On Thursday, expecting another day of large diurnal changes in temps, with temperatures quickly rising into the 70s by noon thanks to a shallow inversion, increasing SW winds and steep low level lapse rates. Thermal ridge takes aim at central IN with +13C at 850mb by 18Z. High temperatures as a result are expected to be 15-20 deg above normal from the upper 70s to near 80. For reference the record high for Indianapolis on Thursday is 82 set in 1927.

As the cold front pushes south from northern Indiana, sufficient moistening of the BL combined with frontal ascent suggests the potential for light rain showers to occur over northern portions of central Indiana during the late afternoon/evening. NAM is the most bullish of the suite of model guidance, but inspection of the NAM forecast soundings suggest this may be due to the normal NAM over saturation bias in the BL. It does appear prudent to carry slight chance PoPs given the degree of available moisture (dewpts in the mid-upper 50s) and fairly strong convergence along the front. Poor mid level lapse rates owing to mid level subsidence in the wake of the primary shortwave trough axis moving into the eastern Great Lakes will preclude any TS chances.

Friday through Friday Night...

The surface frontal boundary is expected to undergo frotolysis across the Ohio Valley early on Friday. The presence of upper ridging building in from the west ahead of weak shortwave trough moving through the southern Plains, combined with surface high pressure centered over the Great Lakes, will lead to much more quiescent weather on Friday across central Indiana. By Friday night, the lead shortwave is expected to approach the MS valley. There is some signal for enough mid level saturation to occur where the greatest height falls/weak FGEN forcing occur, that some light showers will be possible across northern zones Friday night.

Saturday through Sunday...

As the lead shortwave trough moves through the upper ridge, with limited low level response seen on guidance, the consequent effect will be widespread mid-high level cloud cover on Saturday with little to no precip chances expected except early in the far north. There is a high degree of model uncertainty with regards to the precip potential for Sat night into Sunday. The GFS has a much stronger secondary shortwave (current well west of the Baja CA coast) moving across the MS valley into the Ohio Valley Sat night into Sunday. In particular the GFS has a much stronger 850 mb jet that develops over the Gulf Coast, somewhat convectively enhanced, but also supported by barrier jet processes on the fringes of the surface ridge in the Carolinas. As a result, more rapid moisture return by the GFS would support greater QPF across central Indiana. However, ensemble data and the OP Euro are much weaker with the mass fields and consequent QPF amounts and coverage through Sunday. In fact the OP Euro has almost no precip for central Indiana as the shortwave trough undergoes greater deamplification. For now, will play the middle ground with moderate PoPs for the entire forecast area Sat night into Sunday.

Monday through Wednesday...

Not too unsurprising, the differences in guidance becoming amplified with the upcoming phasing/pattern amplification over the western and central CONUS early next week. The GFS is much more bullish with a large closed cyclone developing over the Plains by Monday with strong phasing of the northern and southern streams/shortwaves. While the Euro and other ensemble guidance keep the streams slightly out of phase and pattern more progressive. As a result, the forecast leans more towards the progressive solutions with rainfall chances increasing by Tuesday-Wednesday. Moisture return and quality of instability are the main questions regarding TS coverage and severe potential this far out. However, kinematics will be favorable for some potential severe if instability is higher than currently progged.

AVIATION (18Z TAF Issuance)

Issued at 1258 PM EDT Wed Oct 28 2026

Impacts:

- SW winds gust 18-20 kts Thursday afternoon.

Discussion:

Areas of mid level clouds have dissipated across central Indiana in the last few hours. More mid level clouds associated with a weak disturbance will move eastward overnight with just scattered to brief broken coverage expected. With low pressure far to the north- nw and high pressure centered nearby in the Appalachians, expect light southerly winds through tonight along with VFR conditions.

A stronger storm system over the northern Plains and associated cold front will move into the western Great Lakes on Thursday. Ahead of the front, winds will become more southwesterly with sustained speeds increasing to 10-15 kts with gusts 18-20 kts at KIND/KLAF by midday/16Z lasting through the afternoon. The cold frontal wind shift to NW along with lower VFR ceilings are expected to reach KIND shortly after the end of the TAF period.

IND WATCHES/WARNINGS/ADVISORIES

None.