Marine Weather and Tide Forecast for Apple River, IL

SHORT TERM /THROUGH THURSDAY NIGHT/
Issued at 152 AM CDT Wed Aug 5 2026

An active Wednesday ahead! A shortwave trough is expected to dive into the base of a longwave trough over the region and help spawn widespread showers and storms (70-90% coverage) along and north of a stationary boundary draped across our southern CWA The ingredients are there for heavy rainfall: enhanced diffluent flow aloft, PVA at 500 mb, F-gen in the 850mb-700mb layer, and 1-2 inch PWATs oriented northwest to southeast. Interstate 80 will be the dividing line for the heaviest rainfall with areas south seeing 1-3 inches across two rounds of storms (one in the morning and a second in the late afternoon/evening) while areas north could only see 0.5-1 inch mostly in the morning round. In terms of severe weather, the threat appears limited and uncertain as morning convection and cloud cover is expected to dampen diurnal heating and cut into the available energy for storms; however, areas along and south of Interstate 80 that see breaks in the clouds during the early afternoon could see some modest destabilization in the form of 500-1000 J/kg. There is greater confidence though on the 0-6 km bulk shear with a 80-100% chance for it to exceed 35 knots Wednesday afternoon along and west of the Mississippi River. With all these factors, the SPC does have a Marginal Risk (Level 1 of 5) for the areas along and south of Interstate 80 in the low CAPE, high shear environment. Primary threats will be gusty winds, lightning, and heavy rainfall, but small hail and an isolated tornado cannot be ruled out.

Heading into tonight, the shortwave trough and convection pushes the surface boundary southeastward out of our CWA as dry air advection in the mid-levels begins and high pressure builds in. Isolated showers and storms (20-30% coverage) could still continue into the overnight hours Wednesday along and south of Highway 34, but coverage should decrease by Thursday morning.
Despite the frontal passage, lows will only drop into the 60s with residual surface moisture and cloud cover cutting into the radiational cooling.

Thursday will be mostly dry as surface high pressure camps over the area as the shortwave trough moves to the east. Highs are forecast to barely climb into the 80s with light and variable winds areawide. These conditions are not expected to last long though as the next shortwave dives into the Northern Plains late Thursday night, pushing another weak cold front southward into Minnesota and the Dakotas.

LONG TERM /FRIDAY THROUGH TUESDAY/
Issued at 152 AM CDT Wed Aug 5 2026

Friday...Isolated to scattered storms (20-40% coverage) are back on the table as a surface trough moves through the area.
Limited instability due to the lack of prolonged return flow and WAA should dampen the severe threat with these storms, but the northwesterly flow aloft does put the shear vector perpendicular to the front, leaving the door open to a possible MCS development as noted in the SPC's Day 4-8 Convective Outlook.
By Friday night, the boundary clears the CWA as another weak high pressure moves in.

Saturday...A rinse-and-repeat of Thursday is likely on Saturday as convergence aloft on the backside of Friday's shortwave trough and low-level CAA keep things dry. Highs and lows should be seasonable, but once again, these pleasant conditions will not last.

Sunday-Tuesday...There is a lot of uncertainty in PoPs heading into early next week as persistent west-northwesterly flow aloft prevents any significant moisture advection into the region. What is a little more certain is the shift in low-level flow. Another weak shortwave is forecast to deepen a low pressure on the leeward side of the Northern Rockies and move eastward towards Iowa and Minnesota on Monday. General consensus among ensemble models is a southerly wind shift which will kick off a warming trend Sunday and into early next week with highs likely (60-80% chance per 04.12z LREF guidance) in the mid-80s to low 90s. Any residual boundary left across the region on Tuesday will also play a huge role on the northward expansion of the heat.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
Issued at 621 AM CDT Wed Aug 5 2026

Very short term models are struggling with storm complex along the IA/MO border. Said complex will move east and slowly weaken as it moves away from the better support. The LLJ is forecast to shift east toward the Mississippi River and develop a new storm complex around 18z/05. This new storm complex will then move east into central Illinois. Outside of SHRA/TSRA VFR with pockets of MVFR. MVFR/IFR conditions in the rain and TSRA.

DVN WATCHES/WARNINGS/ADVISORIES
IA...Flood Watch through this evening for IAZ076>078-087>089-098- 099.
IL...Flood Watch through this evening for ILZ024>026-034-035.
MO...Flood Watch through this evening for MOZ009-010.