Marine Weather and Tide Forecast for Olmsted, IL

DISCUSSION
Issued at 229 PM CDT Sun Jun 15 2025

The synoptic setup remains unsettled through the middle of the week as mid-level troughing prevails. A 500 mb shortwave will approach the FA from the west tonight bringing increasing chances of showers and thunderstorms into the day on Monday.
Spatial coverage this afternoon will remain more sparse across southwest Indiana and western Kentucky, but turns more numerous and widespread over the entire FA during the morning hours. The 12z HRRR and HRRR PMM continue to indicate the potential for a narrow swath of 2 to 4 inches over southeast Missouri with up to 1 to 2 inches across the rest of the FA. Given PWATs in the 99th percentile around 2 inches and a warm cloud layer of 13-14 kft AGL, torrential downpours will be probable with the potential for localized flash flooding due to poor drainage and runoff in prone low-lying locations. While the RAP supports 500-1000 J/kg of MLCAPE, the lapse rates are very meager with about 20-30 kts of sfc-6km shear at best. This should inhibit the potential for organized strong storms in the afternoon during peak heating, but a brief stray gusty storm cannot be ruled out.

Moist southerly flow with dewpoints in the lower 70s will support additional chances for showers and thunderstorms on Tuesday and Wednesday with heavy rainfall and localized flash flooding remaining a concern. With that said, Wednesday afternoon into Wednesday night will be more favorable for strong to severe storms as a more amplified 500 mb shortwave ejects across the central Plains with increasing forcing for ascent. In the wake of a sfc cold front that will begin to approach from the northwest, models support 340 to 345K of 0-3km theta-e combined with 2000-3000 J/kg of MLCAPE and a modest 30 kts of deep-layer shear. Given 3-6 km lapse rates between 7.0 to 7.5 C/km and a 25 to 30K max theta-e difference, damaging winds and large hail will be the main hazards of concern as storms will be parallel to the 0-3 km shear vectors. SPC currently has a slight risk progged in their D4 outlook in the far northwest while the CSU-MLP and NSSL-ML guidance is higher with severe weather probabilities for the entire FA. With the better forcing lifting northeast Wednesday evening, uncertain how far southeast severe storms will reach, especially in the vicinity of the Ohio River with waning kinematics and thermodynamics. Overall, the severe risk looks to be more of a lower end one that is typical for the summer months.

While shower and thunderstorm chances may linger into Thursday, a dry weather pattern settles over the FA Friday as a 594 dam ridge of high pressure builds into next weekend. Although this week will certainly be more hot and humid with highs trending into the mid to upper 80s with lows in the upper 60s to lower 70s, the first 90s remains on track to arrive Saturday for much of the region with a 60 to 80% probability progged by the NBM.
Lows at night do not provide much relief in the mid 70s. In fact, NBM heat index values in the lower 100s are not far off from reaching advisory criteria as the heat looks to persist into early next week. The Heat Risk index supports at least moderate heat related impacts.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
Issued at 1155 PM CDT Sun Jun 15 2025

Rain and embedded thunderstorms are working in from the southwest. Impacts at POF and vicinity should continue for a few hours eventually moving into CGI. Its less likely to see bigger impacts through the overnight further east although fog and low stratus could become a factor by around 10z everywhere.

A brief break before another round of showers and storms fires up by 16-18z is anticipated, with most sites in the area getting at least a piece of that. Left it at prevailing shower activity although there will likely be lulls, it definitely appears to be a more on than off type day right now.

PAH WATCHES/WARNINGS/ADVISORIES
IL...None.
MO...None.
IN...None.
KY...None.