textproduct: Indianapolis

KEY MESSAGES

- Wind gusts between 30-40 mph mainly in the afternoon.

- Moderating pattern through the middle of next week with unseasonably mild conditions expected Wednesday-Friday

- Near record high temperatures in the 60s possible on Christmas Day.

FORECAST UPDATE

Issued at 1024 AM EST Sat Dec 20 2025

Minimal adjustments to the ongoing forecast across Central Indiana. The increasing mid-level cloud cover associated with a moisture starved frontal boundary is approaching, but ahead the clouds have arrived and should help to reduce the depth of mixing for this afternoon. There remains a channel of tighter pressure, which in general will allow winds to be breezy at times, but the clouds will help to keep the depth of mixing under control. With low-level flow remaining from the south turning southwesterly, expect a steady rise in temperatures. The clouds may also inhibit temps from climbing quickly and we may not hit peak heating until late in the afternoon. Have held onto mid/upr 40s for the most part this afternoon, could still see a few sites tag 50 but again the cloud cover may inhibit temps from warming much beyond the upper 40s. Frontal passage still appears on track for this evening, which will bring a return to cold- air advection to Indiana. This will cause temperatures to fall back into the 20s.

Upon frontal passage, some added moisture may accompany the cold air but expect any precipitation that does develop to end up as flurries at best. So have held onto a dry forecast at the moment and just mentioning that potential for now.

SHORT TERM (Today and tonight)

Issued at 300 AM EST Sat Dec 20 2025

A strong vort max is currently moving eastward within zonal upper- level flow over the northern Great Lakes. Its corresponding surface cyclone is potent, at roughly 990mb. This system is modeled to race eastward today, dragging a cold front across Indiana this evening. Surface high pressure then builds in bringing quiet weather tonight into Sunday.

Before that happens, however, strong mass response has allowed a potent low-level jet to form. This jet, situated at 925 to 850 mb, will rapidly bring warm air back northward through the morning and afternoon. Despite an Arctic front passing by only 24 to 36 hours ago, we'll see highs climb quickly into the 40s and low 50s.

Additionally, some gusty winds are possible today as weak mixing allows some of the momentum associated with the LLJ to mix downward. Model soundings show a fairly shallow PBL and warm nose aloft, so wind gusts will be limited despite the strong (50-60kt) LLJ just above the surface. Still, a tight MSLP gradient at the surface should promote gusts between 25-35kt at times until the cold front arrives during the afternoon.

Very little moisture advection is shown in guidance, though dew points should gradually push into the low/mid 30s during the afternoon. All the best forcing associated with the trough/low will pass far to our northeast. Thus, no precipitation is expected today.

By tonight, the cold front is expected to pass through between 00z- 06z. Cooler air will slowly seep southward behind the front, allowing for lows in the 20s (low 20s north, upper 20s south).

LONG TERM (Sunday through Friday)

Issued at 319 AM EST Sat Dec 20 2025

Belly of H500 zonal trough to slide east across the Midwest Sunday with corresponding surface polar high pressure keeping a quicker pace while crossing the CWA through the latter half of the weekend. Dry and mostly clear conditions amid lighter breezes will oversee near to slightly below normal temperatures into Sunday night. Progressive pattern will send next, weaker, area of surface low pressure across northern Plains/Great Lakes Monday into Monday night...placing Indiana within a less intense gradient of veering southerly breezes, bringing milder conditions and scattered drizzle/light rain showers for most locations.

The middle of the long term will feature a broad and building upper level ridge that will trend mid-week highs upward through the 50s into possibly the 60s on Christmas Day. Further chances for occasional isolated/scattered rain showers with low-level flow most often from a southerly heading around 10-20 mph...with coverage of showers likely greatest around the late Wednesday/Wednesday night timeframe when deep moisture over 1.00 inch of precipitable water will be most prevalent. Likely a downward trend in POPs around Christmas Day when the upper ridge's heights and associated differential NVA are most likely peaking. Near record high and low readings are possible on Christmas Day.

Seasonably strong dome of polar surface high pressure to grace the north-central US with its southern quadrants by the end of the workweek/period, bringing a more seasonable trend that should equate to slightly above normal readings. Adequate deep Gulf moisture and unseasonably high surface theta-E values will promote at least scattered rain showers, although appears upstream zonal upper pattern would not support any substantive instability. The normal max/min at Indianapolis through the long term are 38/24.

AVIATION (12Z TAF Issuance)

Issued at 631 AM EST Sat Dec 20 2025

Impacts:

- Low level wind shear this morning.

- Gusty S/SW winds peaking between 25 and 30kt this morning into the afternoon.

- Wind shift to NW around 00z.

Discussion:

Passing high and some mid clouds will continue through the period.

A strong low-level jet is developing which will cause a period of low-level wind shear between 45-50kt. Shear will persist into the morning hours.

Surface winds are currently out of the southeast, but will gradually become southwesterly and then westerly this afternoon. Some gusts near 25kt will be common after about 16z with perhaps a gust to 30kt possible.

A cold front is expected to arrive around 00z, which will cause winds to become northwesterly. Speeds may increase a bit behind the front, but should gradually diminish after 06z as surface high pressure moves in.

IND WATCHES/WARNINGS/ADVISORIES

None.