Marine Weather and Tide Forecast for Holiday Shores, IL

SHORT TERM
(Through Late Wednesday Afternoon)
Issued at 406 AM CDT Tue May 13 2025

The Mid-Mississippi River Valley remains beneath the northwestern flank of an upper-level cutoff low still supporting some weakening/dissipating showers across southwestern IL early this morning within low-level moisture converge. With a BL characterized by abundant moisture and light winds, areas of low stratus and fog will continue to increase through the morning. A Dense Fog Advisory is in effect for portions of southeastern, east-central MO and southwestern IL. Fog will dissipate an hour or two after sunrise.

The cutoff low will begin to migrate eastward today, leaving coverage of redeveloping showers and thunderstorms lower than Monday and mainly along/east of the Mississippi River and southeastern MO during midday and afternoon closer to the low. Areas of stratus this morning should lift and become more cumuliform by the afternoon, allowing stronger insolation than Monday and warmer temperatures in the mid-70s to low-80s F. Patchy fog will be possible again late tonight into Wednesday morning with most clouds clearing but with lower coverage since antecedent BL mixing will be relatively deeper.

On Wednesday, a warm front is expected to lift northward through the day, marking the onset of strong low-level WAA and intensifying warming trend with high temperatures reaching the 80s F CWA-wide.
Since an upper-level ridge will be overhead and an arriving EML will begin to intensify a capping inversion, around 20 percent or less of HRRR membership has any precipitation accompanying the warm.
However, a few showers developing below the capping inversion cannot be ruled out within the strong WAA. This strong WAA will support very mild overnight temperatures Wednesday night in the mid-60s to low-70s F, potentially setting the stage for daily record maximum low temperatures to be threatened for Thursday (see CLIMATE).

Pfahler

LONG TERM
(Wednesday Night through Monday)
Issued at 406 AM CDT Tue May 13 2025

A potent upper-level trough will track across the Northern Plains into Upper Midwest on Thursday, forcing a trailing cold front through the Mid-Mississippi River Valley and through the CWA between late morning through early evening. With strong WAA raising 850-hPa temperatures above the 99th climatological percentile, low-level flow veering to southwesterly ahead of the front with some downsloping off the Ozark Plateau, an exceptionally warm start, and upper-level clouds just gradually increasing; well-above average temperatures in the upper 80s to low-90s F are favored, threatening daily records. Although the exact timing of the front varies across model guidance, its timing should not have a significant impact on temperatures due to its Pacific nature and mild post-frontal airmass with very weak low-level CAA. Dry conditions are most likely on Thursday with initiation of any thunderstorms along the front very uncertain due to a strong capping inversion, most robust large-scale forcing passing to the north, and weak moisture converge along the front. These factors aside, IF any thunderstorms can manage to develop, conditions would favorable for them to become severe with very strong instability (MLCAPE of 2500 to 4000 J/kg) and strong deep-layer wind shear of 45 to 60 kt. If any initiation were to occur, ensemble model guidance suggest it would take place across southeastern MO or southwestern IL or locations even further to the east during late afternoon into evening.

On Friday, the front is expected to lift back northward into the CWA ahead of another upper-level trough and associated cold front. With a more southerly track of this trough and weakening of the capping inversion, there is better support for development of showers and thunderstorms during the afternoon and evening with 30 to 50 percent of ensemble model membership depicting measurable rainfall along/south of I-44 (MO) and I-55 (IL). Conditions could again be supportive of any thunderstorms becoming strong to severe with probabilities of 1500+ J/kg of SBCAPE 40 to 60 percent in those areas among 50 to 60 kt of deep-layer wind shear. Exactly when and where thunderstorms initiate is uncertain with the warm front and cold front both potential catalysts. All hazards are on the table but the potential for supercells and favorable thermodynamic profiles for large hail does elevate that hazard.

Global model guidance are in agreement that upper-level flow across the Mid-Mississippi River Valley will become quasi-zonal over the weekend before amplifying again early next week as troughing arrives to the Inter-Mountain West. However, the exact details of this pattern, including mid-level perturbations in the flow and position of a wavering front that impact exact temperatures and when additional opportunities for showers and thunderstorms are present.
Currently, most ensemble model membership has the front south of the CWA on Saturday with the majority having dry conditions accompanying slightly cooler but still above average temperatures. Sunday into early next week, membership with measurable rainfall increases as the more amplified pattern would allow for the front to eventually progress northward and a more active pattern to resume.

Pfahler

AVIATION
(For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1236 PM CDT Tue May 13 2025

MVFR ceilings at UIN will improve to VFR by 19Z. There will be some isolated showers and thunderstorms that could affect UIN/STL/SUS/CPS through 23Z, but coverage will not be great enough to even warrant a PROB30 group at the moment. Fog is expected to redevelop in river valleys again tonight, but is not expected to be as widespread or as dense as it was this morning. I have added 2SM BR to JEF/SUS/CPS between 08-14Z to cover this. Otherwise, just light southeasterly winds are expected through the period.

Britt

CLIMATE
Issued at 227 PM CDT Mon May 12 2025

Record maximum temperatures and warmest minimum temperatures for May 15.

MAY 15

ST Louis: MAXIMUM 94 1944 WARMEST MIN 72 2013

Columbia: MAXIMUM 90 1944 WARMEST MIN 71 1941

Quincy: MAXIMUM 93 1944 WARMEST MIN 69 1962



LSX WATCHES/WARNINGS/ADVISORIES
MO...None.
IL...None.