textproduct: Indianapolis

KEY MESSAGES

- Clouds and isolated light showers/drizzle today

- Warming trend through the weekend...additional periods of light to possibly moderate rain likely Friday into Sunday...and again around Tuesday

SHORT TERM (Today and tonight)

Issued at 300 AM EST Thu Dec 26 2024

Today.

Light rain is expected to continue through the rest of the overnight hours with a gradual tapering down in coverage and intensity towards daybreak with the loss of isentropic lift and as weak subsidence works its way into central Indiana. By mid to late morning any precipitation should be limited to western Indiana with southeasterly surface flow gradually bringing in drier air.

Skies will also begin to clear across the southeastern counties by mid to late afternoon with model soundings showing dry air through around 5kft but saturation above that layer will likely keep at least some cloud cover around through sunset. Temperatures are expected to be warmer today with the expected breaks in the clouds combined with the strengthening southerly flow as highs top out in the low 50s.

Tonight.

Any breaks in the clouds will quickly begin to fill back in tonight ahead of the next rain producing system that is expected to impact central Indiana Friday. The nose of the LLJ will remain southwest of the forecast area through the night, but strong moisture advection between 900mb and 700mb will quickly saturate the low levels again and bring a return to cloudy skies by the morning hours Friday. Rain should hold off until after daybreak with additional details on the rain in the long term section below. Lows will again be mild tonight with temperatures ranging from around 40 near Muncie to the mid 40s towards Vincennes.

LONG TERM (Friday through Wednesday)

Issued at 300 AM EST Thu Dec 26 2024

A winter-like synoptic pattern will be the rule through the long term with a broad, yet rather zonal trough trending slowly eastward across the CONUS. This flow will be progressive, however, with various short waves advancing from the Pacific/western US...and through the central US before lifting northward over eastern North America. Corresponding areas of surface low pressure should be rather weak and track near or northwest of Indiana, with critical temperatures/thicknesses for frozen precipitation gradually trending from southern Canada to the Midwest by the end of the period.

Friday through Sunday...

Another tandem of waves will lift from the Lower Mississippi Valley into the Midwest...bringing more generally damp conditions and probably a couple 6-18 hour periods of more organized light-moderate rainfall. Perhaps the greatest variable will be the potential for heavy rain/storms near the Mid-South which would zap any better precipitable water over 1.00 inch from reaching the CWA. Expect best chances for rain Friday and again Saturday night into Sunday. Confidence in overall moderate rainfall of 0.50 to 1.00 inch is greatest south of I-70 and especially towards the Ohio Valley...with hopefully many northern tier locations still picking up 0.30-0.50 inches of rain by the end of the weekend.

No isolated flood concern so far following removal of ground frost amid recent milder conditions...although will continue to refine low chances for this threat over far southern zones with further updates. SOutherly breezes through Saturday will continue to moderate readings through unseasonably mild levels. The record high max/min for Saturday at Indianapolis are 65/58...the current forecast high/low is 60/51. Low pressure departing into eastern Ontario on Sunday will bring more west-northwesterly moderate breezes in its wake and a modest downward temperature trend.

Monday through Wednesday...

Mainly dry conditions expected for early next week and going into New Years...surrounding what should be briefly widespread light rain for 1-2 periods from another wave, which should this time pass to our northwest into the Great Lakes. A switch from Pacific maritime to more typical northwest flow to start 2025 should return readings to near normal by the end of the long term. Looking past the end of the long term...the pattern may stay somewhat active with further chances for precipitation...although this will be contingent on the position of a broad trough spinning near Ontario...and how its orbiting waves phase while tracking through the CONUS.

AVIATION (12Z TAF Issuance)

Issued at 519 AM EST Thu Dec 26 2024

Impacts:

-Brief periods of MVFR vsbys through 16Z with light rain/drizzle

Discussion:

Light rain will lessen in coverage through the morning with brief periods MVFR to possibly IFR vsbys. There may be a few residual showers after 16Z, but coverage will be minimal afterwards. Cigs will gradually continue to lift into late afternoon with some breaks by mid to late afternoon. Cloud cover will then begin to fill back in late tonight ahead of morning rainfall tomorrow. Winds will generally remain southeasterly at 4-8kts through the TAF period.

IND WATCHES/WARNINGS/ADVISORIES

None.