textproduct: Indianapolis

KEY MESSAGES

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

- Strong front with wind gusts possibly over 50 mph Sunday night into Monday morning along with a few thunderstorms

- Rapidly falling temperatures into the 20s on Monday with wind chill values near zero at times

- Much colder weather through next week with highs at or below freezing

SHORT TERM (This evening through Sunday Night)

Issued at 108 PM EST Sat Dec 27 2025

Rest of Today and Tonight.

The primary focus for the short term period will be tracking a potent system Sunday into Sunday night which will bring showers and storms, strong gradient winds, and a 40+ degree temperature drop over 6 to 9 hours. Through the rest of today, stubborn low-level moisture will remain trapped beneath a persistent subsidence inversion which will help to keep widespread cloud clover locked in place. Satellite imagery shows a broad expanse of low stratus across central Indiana, though a high-pressure system passing to our north is beginning to introduce some slightly drier air aloft . This should allow the inversion to weaken enough to permit some scattered breaks in the cloud deck by late afternoon or evening. However, this recovery will be brief as a deep upper-level low organizes over the Northern Plains which will help to bring increasing strong warm air advection to the area. This moisture surge will help to bring a return to nearly saturated temperatures in the low levels and could bring some drizzle or light fog by daybreak Sunday.

Sunday and Sunday Night.

Sunday will feature a significant synoptic transition as central Indiana enters the warm sector of a rapidly deepening mid-latitude cyclone. A powerful LLJ of 45 to 55 knots will pump an anomalously moist airmass into the region, with moisture content values approaching 1.25 inches. Temperatures will soar into the mid-to- upper 60s with these values at or above records. The forecast high for Indianapolis is currently 68 which is 3 degrees above the record set in 1984. While there may be some daytime precipitation, especially in the northwest ahead of the arrival of better forcing, much of the precipitation looks to be at or after sunset. The overall threat for organized severe weather remains low with extensive cloud cover and poor lapse rates helping to limit surface- based instability and keeping much of the instability elevated. That being said, a line of showers and storms looks increasingly likely which could help to mix down some of the jet level winds and bring a few thunderstorm wind gusts of 50-60 mph. Total QPF with the event will range from around 0.25" to 0.5" in the south to around 0.5" to 0.75" in the north.

Outside of storms, strong gradient winds will also occasionally mix down with gusts of 35 to 45 mph. Confidence in the strongest winds will be across the northeastern counties where the LLJ will be maximized. A Wind Advisory may be needed, but with uncertainty as to the extent of 45+ mph winds will hold off at this time.

After the frontal passage another window for impacts arrives late Sunday night. A sharp non-diurnal temperature curve will see values crash from the 60s into the 20s in around six hours. This presents a risk for a flash freeze. While strong post-frontal winds will help evaporate some surface moisture, any residual standing water on untreated surfaces, particularly bridges and overpasses, will likely freeze rapidly before it can dry along with areas where water had ponded earlier in the night. There also may be a brief period of snow on the backend of the system as temperatures fall, but this increasingly looks brief with only very minor snow accumulations.

LONG TERM (Monday through Saturday)

Issued at 108 PM EST Sat Dec 27 2025

Monday Through Tuesday.

Monday will be a day of transition into a more traditional winter pattern. Central Indiana will reside firmly within a cold air advection regime as the aforementioned surface low departs toward the Great Lakes. Tight pressure gradients will maintain blustery northwest winds with gusts continuing to reach 40 mph through the morning. When combined with ambient temperatures struggling to reach the mid-20s, wind chill values will likely drop to near or slightly below zero. Within the cyclonic flow on the backside of the system, wrap-around moisture will interact with the arrival of the cold air to produce scattered snow showers and flurries. The best chances for minor accumulations will be focused north of the Interstate 70 corridor, where deeper moisture and better lift are expected.

Wednesday Through Saturday.

The middle of the week features a period of relative quiet as a large polar high-pressure system slides across the Midwest. This will keep temperatures well below seasonal averages on Wednesday, though the airmass will be significantly drier, leading to more sunshine. The main concern for midweek will be the potential for some lake-effect cloudiness or a stray flurry to drift into our northernmost counties, though the fetch across Lake Michigan appears unfavorable for any significant inland penetration.

Looking toward the end of the year, New Years Eve is shaping up to be frigid but dry. Clear skies and light winds associated with the center of the high pressure will facilitate efficient radiational cooling, likely dropping overnight lows into the lower teens for the midnight celebrations. A weak clipper-like system may approach the region by Friday or Saturday, potentially bringing a return of light wintry precipitation. However, there is significant ensemble divergence regarding the timing and strength of this system, so for now, the forecast reflects only low-end chances for light snow or rain to kick off the first weekend of 2026.

AVIATION (18Z TAF Issuance)

Issued at 108 PM EST Sat Dec 27 2025

Impacts:

- IFR cigs briefly MVFR late this afternoon before IFR returns after 02Z - Brief MVFR vsbys due to non-dense fog and light rain late tonight - Showers possible towards LAF tonight and early tomorrow - Southerly wind gusts to 20kts tomorrow morning, to 30kts in the afternoon

Discussion:

IFR cigs continue across central Indiana with a persistent stratus deck. Vsbys have improved to VFR and will remain VFR for much of the period outside of some light rain and non-dense fog late tonight. Cigs will briefly improve to MVFR late this afternoon with a low- chance for VFR before dropping back to IFR after 06Z. There may be a few showers towards LAF tonight and early tomorrow but otherwise rain chances look minimal until later in the day. Southerly winds will begin to gust tomorrow morning with wind speeds increasing through the day.

IND WATCHES/WARNINGS/ADVISORIES

None.