Marine Weather and Tide Forecast for Elsah, IL

SHORT TERM
(Through Tuesday Night)
Issued at 247 AM CDT Mon May 12 2025

Water vapor imagery this morning shows that the Rex Block that has been driving our weather the last couple of days is beginning to break down as the block's cutoff is moving northward toward the Middle Mississippi Valley as a trough edges into the ridge across the Intermountain West. With the northward drift of the cutoff, moisture is deepening and lift is increasing across the CWA, resulting in the arcing band of showers and thunderstorms moving into the area from the southeast. As the cutoff moves north- northeastward through the day, scattered showers and thunderstorms will continue to move southeast to northwest across the CWA, with the greatest coverage expected across southeastern Missouri and southwestern Illinois where moisture and lift are greatest.

As the greater lift moves eastward this evening and instability wanes with the setting sun, convective coverage will decrease, with a lull expected overnight. With the cutoff drifting into the Ohio Valley tomorrow and weakening, lift will continue to decrease across the CWA However, there may be enough lift paired with afternoon instability to produce widely scattered showers and perhaps a thunderstorm if convection can break the cap noted in several model soundings. As with Monday, convection will diminish as instability decreases with the onset of evening.

Elmore

LONG TERM
(Wednesday through Sunday)
Issued at 247 AM CDT Mon May 12 2025

As the cutoff continues to move northeastward away from the region on Wednesday, southwesterly flow will become increasingly established over the Middle Mississippi Valley. Within this southwesterly flow, warmer air will advect into the region aloft, with 850 mb temperatures climbing to right around 15 degrees C per ensemble means. This is a degree or two cooler than previous initializations, and surface temperatures have correspondingly come down as well, with ensembles clustering in the mid 80s for most locations Wednesday afternoon. Heat only builds on Thursday as 850 mb temperatures surge to around 20 degrees C ahead of a system moving through the Midwest, correlating with surface temperatures around 90 degrees.

The system on Thursday continues to be reflected in the majority of guidance, as a leading shortwave within an upper-level trough quickly moves through the Northern Plains and Upper-Midwest, its surface low following a similar trajectory. A Pacific cold front associated with this low is set to sweep through the Middle Mississippi Valley during the day Thursday. Ahead of this front, guidance consensus remains that SBCAPE could climb as high as 3,000- 4,000 J/kg among deep layer shear of 40 kts or more - a potent environment for severe thunderstorms. However, there still remain several limiting factors for convective initiation, such as capping, poor low-level lapse rates, lack of moisture in the low to mid- levels, and upper-level clouds seen in several soundings. Therefore, confidence in convective initiation, and therefore severe thunderstorms, remains very low. However, if storms are able to form, the environment will support strong to severe storms.

The trough continues to phase eastward on Friday as subsequent shortwaves round its base. A second cold front looks to move through the region, but whether or not convection forms along it in our CWA will depend on its speed and thusly, its location during peak heating or when the low level jet ramps up in the evening.
Confidence is increasing that this cold front will make it through the CWA Friday before it stalls, as ensemble means continue to cool temperatures Friday through Sunday relative to Thursday's warmth.
Given quazi-zonal flow aloft through the weekend, the front is likely to drift about the region, leading a threat for repeated rounds of convection if the front is close enough to the region.

Elmore

AVIATION
(For the 12z TAFs through 12z Tuesday Morning)
Issued at 536 AM CDT Mon May 12 2025

A slow moving weather system is moving into the area this morning, and will bring periods of rain chances to the local terminals today. The best chances through the day are at KSUS, KSTL, and KCPS. There is also a low chance for thunderstorms at all local terminals this afternoon, which could bring visibilities lower than what is currently in the TAFs. While the chance for showers and thunderstorms ends this evening, ceilings will gradually decrease overnight, with MVFR flight conditions expected area wide early tomorrow morning. Fog is also possible for some of the local terminals tomorrow morning, but confidence in where and when this might occur is very low.

Elmore

CLIMATE
Issued at 1048 PM CDT Sun May 11 2025

Record maximum temperatures and warmest minimum temperatures for May 14 and 15.

MAY 14 MAY 15

ST Louis: MAXIMUM 93 2013 94 1944 WARMEST MIN 73 1915 72 2013

Columbia: MAXIMUM 90 2022 90 1944 WARMEST MIN 67 1941 71 1941

Quincy: MAXIMUM 94 1915 93 1944 WARMEST MIN 66 1932 69 1962



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