textproduct: Indianapolis

KEY MESSAGES

- Temperatures warming this week to well above normal

- Rain chances return late week with the potential for a stronger system Thursday into Friday

SHORT TERM (This evening through Monday)

Issued at 308 PM EST Sun Jan 4 2026

Surface analysis shows low pressure developing over the northern Plains this afternoon. Satellite shows extensive cloud cover ahead of the developing system spreading eastward into the Great Lakes. High cirrus has already reached Indiana, and further thickening and lowering cloud bases is expected. No precipitation is anticipated from this system, given its clipper-like appearance. Most of the precipitation will be along and just north of the low's eventual track.

Guidance shows a modest low-level jet (between 30-40kt at 925mb) developing overnight as the system approaches. Though boundary layer stability will limit momentum transfer to the surface, a gradually tightening MSLP gradient will promote a 5-10kt wind overnight. This, combined with cloud cover, should keep temperatures warmer than last night.

Clouds gradually clear on Monday as the system departs, leaving Indiana under mostly clear skies. High cirrus should be present much of the time, however, especially further north. Solar insolation should encourage boundary layer mixing which will finally allow for some downward transfer of faster winds just off the surface. A southwesterly wind gusting to between 15-25kt is likely on Monday. High temperatures will be quite a bit warmer than today, with highs near 50 for most locations except over our far north and northeastern counties.

LONG TERM (Monday night through Sunday)

Issued at 308 PM EST Sun Jan 4 2026

A relatively warmer and more progressive pattern takes shape this week across the Central US; however with this set up comes numerous chances for rain by the end of the week. Upper ridging over much of Central North America shifts to a more zonal flow pattern by the middle of this week before ridging redevelops over the Northeastern CONUS toward the weekend. The overall storm track remains north of Indiana for the next several days with each passing system bringing warmer air further north into the region while colder airmasses remain locked up in Canada and Alaska for the time being. The main focus in the long term will be on the end of the week and into next weekend as a southwesterly flow pattern brings numerous systems into the Ohio Valley and Great Lakes with several waves of rain expected as well as above normal temperatures ahead of a strong cold front.

Tuesday and Wednesday...

Lower pressure over the Plains and high pressure shifting east bring low level westerly/southwesterly flow into the Ohio Valley and lower Great Lakes. Warm air advection aloft will take time to translate to the surface as a strong low level inversion keeps a slightly cooler and damp airmass stuck near the ground. Moisture advection within the "warm" sector Tuesday may be deep enough to saturate the near surface as a vort max overhead and lift from the left exit region of the jet squeeze out drizzle and maybe very light rainfall. Went below guidance for temperatures Tuesday, keeping low clouds around much of the day with the chance for drizzle. Expect highs stuck in the upper 40s to near 50 along and northeast of the I-74 corridor, while highs near 60 are possible further south and west, especially if clouds do break up earlier than forecast.

Weak low level ridging moves in overhead Wednesday with surface high pressure passing by just to the south. Expect low clouds and left over moisture near the surface to stick around at least through Wednesday morning before drier air and boundary layer heating work to clear out low stratus. The overall airmass Wednesday will be a few degrees cooler behind the departing low, but with greater solar insolation and clearing skies, highs may actually be a few degrees warmer on Wednesday with widespread highs in the mid to upper 50s.

Thursday through the weekend...

The main focus in this discussion will be the latter half of the week into the weekend as a strong southwest flow pattern develops over the Central CONUS, setting the stage for numerous systems to bring warmer conditions and rain locally.

Longer range guidance and ensembles continue to portray the phasing of the northern and southern branches of the jet as deep positively tilted trough develops over the Southwest with southwest flow ahead of it. Low level flow becomes southerly Thursday opening up the Gulf for moisture advection northward into the region while a strong surface low develops on the Lee side of the rockies with a warm frontal feature extending northeastward into the Ohio Valley. This is a classic set up for multiple rounds of heavy rainfall in the region. Lower confidence exists in the exact location and timing of the front and associated smaller waves riding along it; however higher confidence exists in the overall synoptic pattern taking shape. WPC has already placed portions of Western Indiana in a marginal risk for heavy rain for the Thursday-Friday timeframe.

Will have to monitor closely where exactly the warm front sets up as waves riding along it may produce several rounds of moderate to heavy rainfall Thursday through Saturday. Indiana does look to be in the vicinity of the front and these features, so keeping rain likely wording in the forecast for now and will fine tune details in the coming days. With the region likely within the warm sector, expect well above normal highs in the 50s and possibly 60s into the weekend despite widespread rainfall around.

There are still several days for details to change, so keep checking back on the latest updates on this week/weekend's warm up and heavy rain threat.

AVIATION (00Z TAF Issuance)

Issued at 612 PM EST Sun Jan 4 2026

Impacts:

- Marginal LLWS between 35-40 kt overnight, transitioning to gusts tomorrow mid-morning into early afternoon.

- Possible MVFR ceilings Monday afternoon/evening.

Discussion:

Despite the relatively far away proximity to the TAF sites, a storm system over the northern Great Lakes will induce a low level jet over the region later tonight. General rule of thumb is 35 kts of shear below 015 for marginal LLWS conditions, or 40 kts below 020. Based on forecast soundings, it does appear we are just in the marginal realm of LLWS to include at all the TAF sites after 06Z until 12Z.

As the boundary layer warms, steeper lapse rates should bring the stronger winds aloft down to surface with SW gusts over 20 kts for at least a few hours between 14 and 19Z. Winds begin to decrease throughout the boundary layer beyond 19Z and insolation also is expected to decrease, therefore expecting surface gusts to drop by then.

The next concern will be the potential for MVFR ceilings. The NAM is the biggest outlier with widespread MVFR ceilings 015-020 developing by midday through the remainder of the forecast period. Granted there is likely to be some moisture advection and even some convergence with the 925 mb trough passage. A blend of RAP/SREF and GFS suggests that SCT025 looks to be the most prudent forecast for the time being. Otherwise, the only other features of note are a high mid deck clouds which will end overnight with increasing cirrus clouds tomorrow afternoon.

IND WATCHES/WARNINGS/ADVISORIES

None.