Marine Weather and Tide Forecast for Urbana, IL

DISCUSSION
Issued at 330 AM CDT Wed Jul 15 2026

Weak 1020 mb surface high pressure ridge over Iowa and ridging over central IL has brought clear skies and calm winds to CWA
With temps cooling to near dewpoints in the upper 60s to around 70F, we are seeing patchy shallow ground fog developing past few hours over the area. Latest model guidance like the HRRR, RAP13 and GFSLamp show patchy fog continuing to develop over central IL through sunrise and could get locally dense in spots especially south of I-74 to along I-72. The patchy fog should lift quickly by mid morning similar to past few mornings. May see patchy fog redevelop overnight into early Thu morning, though latest CAMs show less visibilities restrictions over CWA overnight than what they are showing early this morning.

A Rex Block pattern continued over the central and eastern US with a strong upper level ridge over the upper Midwest into the Ohio river valley, and a weak upper level low/trof over the Southern States. This has brought dry and very warm weather to central/se IL during the past few days along with a heat wave at mid week. The strong 500 mb high to remain just north/ne of CWA with our 500 mb heights of 594-597 decameters today (highest ne of I-74). This should continued dry and hot weather today with mostly sunny skies as few to scattered cumulus clouds (3-5k ft bases) appear later morning/afternoon. Isolated convection should stay south of CWA over southern IL this afternoon/early evening mainly south of I-64. Highs in the lower 90s today with dewpoints in the low to mid 70s, giving afternoon heat indices peaking from 97-103F, highest from I-74 north. This will fall a few degrees shy of heat advisory criteria of 105F though heat advisories this afternoon are not too far away in central and northern Indiana along with air quality alerts (air quality alerts go into northeast IL too today and evening). Muggy lows overnight in the lower 70s.

A weak disturbance moving into the mid MS river valley Thu to gradually bring deeper tropical moisture northward into central/se IL later tonight and Thu as PWATs increase to 1.75-2.2 inches Thu afternoon with weak SSW flow. Models continue to show isolated to scattered showers/thunderstorms developing over central/southern IL Thu afternoon. We have 20-40% chance of convection over CWA Thu afternoon, highest over southern/sw CWA with the higher pops over southern/sw IL where WPC Day2 has marginal risk of excessive rainfall. Canadian wildfires near the MN border is sending smoke southward across WI/MI today and into northeast parts of IL/IN tonight into Thu as backdoor cold front moves into northeast IL tonight. We could see some smoke aloft moving over central IL into Thu which will increase our cloud cover some but the surface smoke and air quality issues should mostly stay ne of CWA through Thu. Highs Thu in the lower 90s with afternoon heat indices in the upper 90s/lower 100s again.

The weak upper level trof/disturbances moves over IL on Friday and brings our best chances of convection (60-80%) especially Fri afternoon. WPC Day3 ERO has marginal risk of excessive rainfall over CWA on Friday especially afternoon hours. PWATs are very high on Friday, from 2-2.4 inches. We have quarter to half inch of qpf on Friday from IL river east and tenth to quarter inch west of the IL river. Though some spots may see 1-2 inches or more in a short time with slow moving cells. We have moderately strong instability but weak wind shear Fri, so a few storms could produce gusty winds/wet microbursts. May also see strong cells Thu afternoon though best chance would be sw IL. Highs Friday in the upper 80s to near 90F and afternoon heat indices in the upper 90s to around 100.

Models are trending slower with existing this weak disturbance on Saturday so we will likely continue chances of convection especially eastern IL Sat afternoon. Another hot and humid day Sat with highs in the lower 90s and afternoon heat index readings peaking around or just above 100 degrees. A weakening cold front dropping down through northern/ne IL toward central IL Sunday but still very warm and humid with highs in the upper 80s to around 90F. SW flow on Monday returning the hot /humid air mass over central/se IL before a stronger cold front moves through Mon night into Tue bringing cooler and less humid air back into the region for middle of next week (next Tue-Thu). Also have 20-30% chance of convection Mon and Monday night and may linger chances into Tuesday.

The Climate Prediction Center (CPC) 8-14 Day Outlook for July 22-28 has a 33-40% chance of below normal temperatures over IL while precipitation during this week is trending near normal.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
Issued at 530 AM CDT Wed Jul 15 2026

Patchy shallow ground fog has affect SPI past few hours with visibilities as low as 1-2 miles. Nighttime Microphysics satellite imagery shows this fog over parts of central IL especially near rivers. Have tempo MVFR vsby until 13Z over central IL airports and having vsbys down to IFR at SPI.
Otherwise few cumulus clouds with 3-5k ft bases to appear after 15Z and dissipate around sunset with scattered cirrus tonight.
The smoke plume from Canadian wildfires was drifting southward over central and northern parts of WI/MI and could see some of this smoke layer aloft into central IL overnight into Thu.
Though smoke near surface affecting vsbys will stay ne of central IL closer to Rockford and Chicago area overnight.
Otherwise more patchy ground fog with MVFR vsbys possible overnight especially along I-72 airports. Light and variable winds to prevail next 24 hours through 12Z/7 am Thu with nearby weak surface high pressure ridge over Iowa and ridging over central IL.

ILX WATCHES/WARNINGS/ADVISORIES
None.