textproduct: Indianapolis

KEY MESSAGES

- Rain moves through this morning; additions rain showers transitioning to a rain/snow mix is expected the afternoon

- Wind gusts of 30 to 40 mph throughout the dayinto

- Accumulating snow likely Thursday night into Friday

- Arctic outbreak expected this weekend with low temperatures near or below zero...and potentially dangerous sub-zero wind chills

SHORT TERM (Today through Friday)

Issued at 250 AM EST Wed Dec 10 2025

Today through Thursday afternoon:

Central Indiana will now face a succession of Alberta Clipper lows over the coming days, the first of which reached the Great Lakes region last night, and the last of which will move through on Saturday. Todays low, will be strong, but will pass well to the north, keeping temperatures well above freezing (currently 42 in Indianapolis), minimizing overall impacts to central Indiana. Numerous showers are expected to pass through most of central Indiana throughout the morning hours ahead of a strong cold front. Total rain amounts for central Indiana are likely to be less than a quarter inch. Despite less overall impacts, the strength of this system will still have some, mostly due to strong winds. A robust jet streak will not be far off the surface around 50-60kt, but an inversion will keep the worst of the winds away from the ground; still gusts in the 30 to 40 mph range are possible throughout the morning. As the inversion breaks some late this morning into the early afternoon, a few gusts may exceed 40, but the jet streak should be east of central Indiana by the time greatest mixing occurs.

The bulk of the lift will be east of the area by 15Z today, but there still will be some modest vorticity advection within the parent trough, along with modest lapse rates that likely will lead to scattered showers at times late this morning through the afternoon. This second round of precipitation will be undercut by some strong CAA during the afternoon hours, of which will likely lead to some mix of rain and snow at times. This should not accumulate to much of anything, but a quick light coating of slush within strongest showers is possible. Winds will continue to be gusty with the tight pressure gradient and cold advection promoting mixing down of stronger winds aloft. Wind gusts around 40 mph are likely, especially north.

The strong push of CAA along with lingering stratus in the broader cyclonic flow will likely lead to scattered flurries this evening through early portions of tomorrow. These flurries likely will not cause any impact. That said, further NE, enhanced low level moisture downstream of Lake Michigan could allow for a few stronger snow showers to develop within this same synoptic setup. These snow showers still likely wont cause much impact but a dusting of snow is possible tonight into tomorrow in the Muncie, Winchester region.

Thursday evening through Friday morning:

As stated, central Indiana will remain in the path of strong upper level NW flow, and an efficient set up for quickly developing lows out of the Canadian Rockies. The second of these systems is expected to pass through late Thursday through Friday morning. The previous system brought through strong CAA, of which will sink the baroclinic zone southward placing central Indiana in a goldilocks zone for both cyclogenesis and temperatures cold enough for snowfall. This second low will be weaker than Wednesday's system, but will likely still have just as much forcing as it pushes across a strong baroclinic zone.

These clipper systems along strong temperature gradients typically produce narrow corridors of moderate QPF, and this one is expected to be no different. The emphasis is on narrow, as this will lead to a wide range of QPF outcomes in certain locations, with still almost 48 hours until snowfall onset. This means take each forecast with some potential of error, as the greatest axis of snowfall could move 25-50 miles depending on where the baroclinic zone is placed following the cold push after today's system. Currently, this axis is most likely to be along the I-74 corridor.

Model soundings showcase a deep isothermal layer as the low arrives between -6C and -10C. This isn't the most ideal temperature for efficient dendrite growth, and therefor SLRs are currently expected to be somewhere between 10-14:1 across central Indiana. This in combination with 0.2-0.3 inches of QPF puts the highest likelihood of snowfall to be between 2 and 4 inches. Slightly higher amounts are possible where the strongest frontogenetical forcing occurs as this forcing will likely be slightly further aloft and within more ideal DGZ temperatures.

Forecast timing has a bit more confidence, as the margin of error is larger and ensembles have a tighter spread. Currently snow is expected to reach the Indiana border between 4-7PM on Thursday and continue through 10AM on Friday morning.

LONG TERM (Thursday through Tuesday)

Issued at 250 AM EST Wed Dec 10 2025

Cold pattern to trend from unseasonable to anomalous this weekend, before moderation expected by end of the period...with additional light snowfall possible. H500 cut-off short wave to plunge slightly within polar flow this weekend...from south-central Canada, across northern and eastern Great Lakes. Paving a path for associated elongated arctic surface high pressure to build/track from North American Plains during the early weekend...to the Great Lakes/ Midwest by Sunday night.

Vort max speeding around the bottom of the upper cut-off Saturday, from Quad Cities area into Ohio, will induce another clipper-type system. Additional light accumulating snowfall is likely for most of the region within perhaps a 15-hour period around the Saturday to Saturday evening timeframe. Bursts of moderate to perhaps briefly heavy snow are possible, especially north of I-70 which will be closer to supporting forcing.

Arctic ridge to quickly build into central Indiana on the hind legs of Saturday's disturbance, with what should be clearing skies Saturday night promoting readings near/below zero. Very cold conditions...possibly approaching Indianapolis' record low of negative 4 degrees Sunday morning...should last into Monday morning, with highs Sunday held below 15F across most zones...and consecutive early mornings below zero for most locations north of I-70.

Wind chill values to fall to around zero for many spots Friday night, yet only rebound Saturday to 5-15 degrees for most locations. Advisory criteria wind chills are currently forecast for both Saturday night and Sunday night across portions of the region...with wind chills during the day Sunday likely held below zero for some northern counties.

Early workweek to feature noticeable moderation back to more reasonably cold levels...with Monday's max/min readings hopefully both noticeably higher than Sunday's marks. Low confidence in potential for freezing drizzle/rain given weak overrunning set-up with surface readings most likely in the 20s. Long term to end with temperatures possibly climbing above freezing.

AVIATION (12Z TAF Issuance)

Issued at 631 AM EST Wed Dec 10 2025

Impacts:

- Gusty winds 25 to 35kt tonight through this afternoon

- MVFR ceilings with intermittent IFR within SHRASN.

- Rain this morning, then mix of rain and snow this afternoon.

Discussion:

Gusty winds from 25-35 kts this morning through the late afternoon. Following dusk, gusts should begin to subside.

Ceilings have quickly gone down to 2500, and will slowly decrease to 1500 throughout the morning. SHRA and SHRASN will develop late this morning through the afternoon, of which could push VSBY down to 4SM and CIGs to 800ft. Overnight, scattered flurries will be possible at KIND and KLAF, but confidence in occurrence is too low to include in this issuance.

IND WATCHES/WARNINGS/ADVISORIES

None.