Marine Weather and Tide Forecast for Jacksonville, IL

UPDATE
Issued at 1028 AM CST Sat Nov 29 2025

16z/10am radar imagery and area observations indicate that snow has spread across nearly the entire KILX CWA ..except for the far SE around Olney and Lawrenceville. Early reports from where the snow has been falling the longest generally show accumulations of 2-5 inches along/south of a Peoria to Decatur line...with as much as 5-7 inches already on the ground across portions of Sangamon and Morgan counties. Current obs show above freezing temps and a rain/snow mix in the Saint Louis metro, but it will take several hours for these warmer readings to arrive in central Illinois due to a continued easterly component to the wind. As a result, snow will continue to fall across the entire area through early afternoon before gradually mixing with rain along/south of a Rushville...to Taylorville...to Robinson line after 21z/3pm. In addition to the falling snow, SE winds gusting 25-35mph will create areas of blowing/drifting throughout the day. The precipitation is expected to rapidly taper off from southwest to northeast across the area this evening as low pressure tracks into north-central Illinois.
At the same time, surface temperatures will climb above freezing everywhere...except perhaps northwest of the Illinois River around Galesburg. This will allow any lingering light precip to mix with rain before coming to an end. It will also aid in melting some of the snow on area roadways. Storm total snowfall is still expected to range from 6-10 inches across a good chunk of central Illinois...with lesser amounts of 2-3 inches along I-70. Further south, am becoming concerned that Richland and Lawrence counties may receive only trace amounts due to the lack of ongoing precip in those counties and the expected warm-up late this afternoon.

Barnes

DISCUSSION
Issued at 356 AM CST Sat Nov 29 2025

Satellite imagery early this morning shows a mid-level trough digging across the Plains, accompanied by a deepening plume of moisture surging northward up the Mississippi Valley. The surface low pressure, currently centered over west-central Kansas, is forecast to lift toward northern Illinois tonight as the associated mid-level wave pivots across the central United States.
Radar exhibits a broad swath of precipitation wrapping around this system, with its eastern edge just beginning to enter west- central Illinois as of 2 AM CST.

While the 00Z sounding from last night indicated a significant layer of dry air below 700 mb, this layer has now eroded. Regional surface observations confirm strong warm and moist advection developing north of the surface low, with upper-jet diffluence contributing to an expanding area of precipitation.

Snow has been the initial precipitation type, and it is expected to remain the dominant type through the afternoon. This is due to the thermal profile and surface wet-bulb temperature remaining cold enough. A notable trend across the last few model cycles is a less aggressive push of warm air into the I-72 corridor by late afternoon. Consequently, the potential for a rain-snow mix (partial melting through a saturated layer) has been shunted further south, closer to the I-70 corridor. This shift means most of central Illinois is now likely to experience a long-duration, all-snow event throughout the afternoon hours.

No changes were made to our winter storm headlines overnight, and forecast snow totals largely remain intact from yesterday's forecast. If anything, our confidence in forecasting warning- criteria snow across east-central Illinois has increased. We continue to support a broad swath of 5-8 inches of snow in areas north of I-70, with the potential for 9-12 inches in areas near and north of a Macomb-to-Bloomington line. At this point, the greatest uncertainty lies in areas near and south of I-70 where there will likely be sharp cut-off in accumulating snow, owing to the potential for a rain-snow mixture by late afternoon. In such areas, we have maintained between a trace and 4 inches of snow.

Gusty southeast winds today will shift to the west tonight as the surface low lifts across the forecast area. Accumulating snow, combined with wind gusts of 25-35 mph, increases the risk of blowing and drifting snow, occasional whiteout conditions, and sporadic power outages.

Precipitation is expected to decrease to flurries or drizzle from west to east after approximately 6 PM this evening as the system dry slot moves across central Illinois. Overnight, additional snow showers are possible near and north of I-74 where wrap-around moisture re-enters the area, though additional snow accumulation is unlikely to exceed one inch.

After today, we will enter a prolonged period of unseasonably cold weather. It won't necessarily be worthy of a Cold Weather Advisory on any given day, but there is a legitimate chance that temperatures do not warm above freezing at all next week as strong surface high pressure builds in and out of the central U.S. At this time, the coldest period appears to be Wednesday night and Thursday night when wind chill values could fall below zero.

Aside from the cold weather impacts, we continue to monitor the potential for a quick-hitting burst of snow Monday night as a pair of jet streaks phase together over the region ahead of a digging trough. At this point, much of the ensemble guidance supports at least a few inches of snow beneath the jet streak. Fortunately, p-type will not be a concern with this event. We will be plenty cold, and with SLRs closer to 12-15:1.

MJA

AVIATION
(For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1156 AM CST Sat Nov 29 2025

1730z/1130am radar shows a band of heavy snow lifting northward toward the I-74 corridor. Visbys beneath the band have been reduced to 1/4 to 1/2 mile...and am expecting these conditions to spread into KPIA/KBMI/KCMI over the next hour or so. Based on the latest radar trends and HRRR/RAP output, have ended the heaviest snow and raised vibsys back up to 1 mile at KSPI by 22z...then further northeast to KBMI/KCMI by 00z. The snow will likely end as a light rain/snow mix at the I-72 terminals...with dry conditions returning across the board after the 03z-05z time frame. IFR ceilings will persist during the snowfall, with ceilings climbing to MVFR overnight into Sunday morning. Winds will initially be SE with gusts of 25-30kt this afternoon...then will become S/SW and decrease slightly this evening. Once low pressure lifts into the Great Lakes and pulls a cold front through the region, winds will veer to NW and once again gust 25-30kt from around midnight through Sunday morning.

Barnes

ILX WATCHES/WARNINGS/ADVISORIES
Winter Storm Warning until 6 AM CST Sunday for ILZ027>031- 036>038-040>057-061.

Winter Weather Advisory until 6 AM CST Sunday for ILZ062-063- 066>068-071>073.