textproduct: Central Illinois

KEY MESSAGES

- Drizzle, overcast skies, and occasional fog will be common through this evening.

- Mild temperatures and daily chances for precipitation will continue through early next week followed by temperatures moderating back to near normal by midweek.

DISCUSSION

Issued at 330 AM CST Thu Dec 26 2024

Water vapor imagery early this morning shows upper ridging centered over the Great Lakes Region with troughing over the western US. Surface ridging extends west through the middle Mississippi Valley with a stationary/warm front draped over central Illinois from roughly north of Macomb to Hoopeston. Low-level moisture remains trapped beneath a subsidence inversion, which has kept skies overcast the last couple of days. Broad isentropic ascent between the 280-290K surfaces continues to support widespread patchy drizzle, with similar conditions expected to persist through this evening. Visibilities have fallen with drizzle and also with fog. The lowest visibilities reside west of the Illinois River where observations show 1 to 3 miles as of 3 am, though sub 1 mile observations are within reach of the county warning area. There is at least a 50% chance that visibility could fall below 1 mile or lower through mid morning, and if this occurs a Dense Fog Advisory may be needed.

A much wavier pattern sets up late this week through early next week as an upper trough emits several shortwave impulses toward the area. The first will bring light rain late tonight into Friday with another right on its heels Friday night into Saturday morning. Additional waves will bring rain showers Saturday night into Sunday morning (for some) and Monday night. Deterministic guidance still favors the Saturday night wave's surface low tracking through the Ohio Valley, which would keep any threat for storms east and southeast of here. Total rain through early next week will be beneficial with 0.5-1 inch currently forecast.

Temperatures will remain above normal through Monday then begin to moderate back to seasonal normals by midweek. Upper flow will transition to northwesterly later in the week as surface high pressure settles into the Plains states. Temperatures turn colder late next week, with colder than normal temperatures favored into the first week or two of the New Year.

NMA

AVIATION

(For the 12z TAFs through 12z Friday Morning) Issued at 505 AM CST Thu Dec 26 2024

A combination of low stratus, drizzle, and fog will keep ceilings and visibilities poor much of today. Some improvement should arrive this afternoon as ceilings begin to improve to MVFR, and then eventually VFR briefly overnight. A surface low will approach the middle Mississippi Valley late tonight into Friday, bringing the return of MVFR or worse conditions. Light rain will lift north out ahead of the low with PROB30 groups added at KSPI and KDEC between 10-12Z. Winds will be light out of the southeast through the TAF period.

NMA

ILX WATCHES/WARNINGS/ADVISORIES

None.