textproduct: Indianapolis

KEY MESSAGES

- Near seasonal temperatures today; potential first 40 degree day for Indainapolis since November 26th.

- Numerous light rain showers tonight into Wednesday, transitioning to occasional snow showers late Wednesday through Friday

- Arctic outbreak expected this weekend with low temperatures down to near zero and potentially dangerous sub-zero wind chills

SHORT TERM (Today and tonight)

Issued at 237 AM EST Tue Dec 9 2025

Central Indiana is currently in a transition zone with strong SW flow impinging on a departing area of high pressure. This has resulted in very weak frontogenetic forcing just north of the area, of which is producing low clouds and light snow. This area of snow may clip far northern portions of central Indiana between 08-11Z this morning, but a majority should fall to the north. Any snow that does fall will likely not accumulate much, and therefor no impacts are expected.

Following this, SW flow will increase rapidly, with surface winds expected to become sustained at 10-15mph with gusts up to 30MPH beginning shortly after dawn, but continuing throughout the day. There will be strong WAA within this SW flow, leading to near seasonal tempertures for the first time since before Thanksgiving. Current expectation is for afternoon highs around 40 degrees near Indianapolis, with slightly high temperatures to the south and lower to the north.

Despite the strong SW flow, the upper level pattern will remain similar, with clipper lows forming downstream supergeostrophic jet streaks in the Canadian Rockies. Tonight's low, will be much stronger than previous iterations, but will pass well to the north minimizing impacts to central Indiana. Still, numerous showers are expected to pass through most of central Indiana tonight ahead of a strong cold front (more on this in the long term). Total rain amounts for central Indiana are likely to be less than a quarter inch.

LONG TERM (Wednesday through Monday)

Issued at 237 AM EST Tue Dec 9 2025

Wednesday through Friday...

Wednesday's robust winds, gusting over 30 MPH, will veer from southwest to west-northwest, bringing a transition from seasonably cool and damp conditions, back to mainly subfreezing, yet reasonably cold conditions through the end of the workweek.

A potent 990 mb surface low, tracking east across the southern Great Lakes Wednesday, will quickly drag its cold front across central Indiana during the morning. Light rain will mix with and change to snow showers through the midday and afternoon hours from north to south, as temperatures fall through the 30s during the afternoon. Vort max embedded within backside of the departing wave should help coverage of flurries and snow showers increase around the late day and evening timeframe, especially over northeastern zones that may catch a lake-enhanced fetch. Very light or no accumulation is expected, with minor impacts possible on untreated roads Wednesday night.

Wednesday's earlier-day maximum readings, in the low to mid-40s, will be the last near-normal highs for at least a week as stagnant cold to very cold pattern returns through mid-month. A less pronounced polar surface ridge will slowly build into the Midwest for the late workweek, with higher confidence in afternoons peaking near 30F/overnights down to upper teens to mid-20s, and lower certainty in timing/coverage and amounts/light accumulations of any snow showers around the Thursday night timeframe that could produce a thin coating for some areas.

Friday night through Monday...

Continued cold pattern to turn frigid this weekend as elongated arctic air mass slowly builds into Indiana from its southeastern corner on Friday night to the ridge's center by the Sunday night timeframe. A bit of overriding Gulf moisture will likely provide considerable cloudiness through at least the first half of the weekend, including flurries to possibly light accumulating snow from what should be an embedded clipper-type weakness crossing the northern Midwest Saturday, ahead of the core of cold air.

Less cloud cover for the Sunday-Monday timeframes as the dome slides east over the region should assist the lowest temperature readings. Highs to be as low as 15-25F for most areas on both Saturday and Sunday, with probably three very cold nights into the early workweek featuring generally single digits north and 10-15F south. Corresponding wind chills will range between values as low as the negative single digits to single digits. Assuming the arctic high continues progressing eastward through the end of the long term, hopefully a noticeable moderation back to near the freezing mark will be on tap for the early week.

AVIATION (06Z TAF Issuance)

Issued at 1237 AM EST Tue Dec 9 2025

Impacts:

- Mixed precip possible late tonight at KLAF.

- MVFR ceilings lowering to IFR tomorrow at KLAF.

- MVFR ceilings developing elsewhere tomorrow morning.

- Gusty winds from the SW at 20-23 kts developing between 12-16Z at at all terminals.

Discussion:

Ahead of a storm system moving through the Great Lakes, winds will increase aloft late tonight. Speeds will generally be between 25-30 kts only 1kft AGL, not quite sufficient for LLWS. With the increase in winds will come increasing warm/moist advection and increasing clouds. Forecast soundings indicate ceilings falling to lower end MVFR during the morning hours at all terminals with IFR conditions expected to develop at KLAF. Despite the presence of cloud cover, sufficient mixing of the winds is expected to develop towards the surface during the morning hours with gusts from 20-23 kts until late afternoon.

In addition to the increase in cloud cover, sufficient moistening will support some scattered precip developing near KLAF, with a rain/snow mix between 08-12Z. Another round of precip is expected to develop later tomorrow evening, just in time for the freighter push at KIND. Soundings indicated ceilings will be just above IFR for IND at this time.

IND WATCHES/WARNINGS/ADVISORIES

None.