Marine Weather and Tide Forecast for Cuba, MO

SHORT TERM /THROUGH WEDNESDAY/
Issued at 239 AM CDT Tue Aug 4 2026

A surface anticyclone has slid eastward into the northeast, with a ridge axis extending westward into southeast Missouri/southwest Illinois. GOES-19 nighttime microphysics imagery along with surface observations show fog across these areas, mainly confined to river valleys. Similar to yesterday, any fog should quickly evaporate within an hour or so after sunrise. A mostly sunny sky is expected for the remainder of the day, with temperatures a few degrees on average warmer than yesterday.

LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/
Issued at 239 AM CDT Tue Aug 4 2026

(Tonight - Thursday)

Increasing mid/high level clouds are expected by this evening as a midlevel shortwave trough moves into the Upper Midwest. At the surface, a cold front is expected to gradually progress southeastward into northeast Missouri and west-central Illinois after 0600 UTC. A few showers, and possibly a rumble or two of thunder, are expected overnight in these locations. Due to the aforementioned increase in cloud cover, lows tonight will be on the milder side, generally in the mid 60s to low 70s.

Chances of showers and thunderstorms increases by midday on Wednesday as another midlevel shortwave trough moves across the central Plains.
This trough is expected to be further south than its predecessor, with the strongest mid/upper level forcing for ascent focused across northeast Missouri and west-central Illinois. This is also where the surface boundary should be located at this time, so widespread showers and thunderstorms are expected. The exact timing of this wave varies a few hours amongst deterministic guidance, but has sped up compared to what it looked like yesterday. That means there should be quite a bit of showers and storms earlier in the day, which also means a bit less instability to work with. The latest HRRR joint probabilities for at least 1000 J/kg of SBCAPE and 30+ knots of deep-layer shear do peak in the 50-70% range from central Missouri northeastward through west-central Illinois however. Multicell clusters are likely to be the preferred convective mode, though a few transient supercell structures are also possible. Damaging winds are the main threat, though some guidance suggests a weak surface low transversing the surface baroclinic zone. There may be enough low-level shear/helicity near the track of that low to yield a low threat for a brief, weak tornado.

Instability weakens after sunset, with the severe threat likely ending shortly thereafter. A west/southwest 20-25+ knot low-level jet is expected to develop overnight Wednesday night, bringing increasing moisture convergence to parts of the area. The coverage of showers and thunderstorms should increase again as a result overnight, first near the I-70 corridor before activity gradually sinks southward as the low-level jet veers more to the west/northwest. There is a concern for some training, with the jet oriented nearly parallel to the surface boundary in an environment favorable for efficient warm rainfall processes (deep warm cloud depths, precipitable water values > 90th percentile of climatology). Locally heavy rainfall is the main concern late Wednesday night into very early Thursday morning.

There likely will be a lull in activity late Thursday morning into the afternoon as the low-level jet weakens. The location of the surface front may be a focused for additional development by the afternoon as diurnal instability increases. Another midlevel shortwave trough is forecast to move out of the mid-Missouri Valley Thursday night. This feature combined with a strengthening low-level jet is expected to yield another uptick in shower and thunderstorm activity late Thursday night. The best chances (40-60%) are near and just north of the expected location of the surface boundary, which is expected to be across southeast Missouri and southwest Illinois. Guidance suggests that the front may wash out a bit by Friday afternoon, but wherever it is may have enough convergence to produce additional showers and thunderstorms.

(Friday Night - Monday)

Ensemble guidance is in a bit better agreement heading into the weekend, showing an amplifying mid/upper level ridge across the Rockies/Plains. We will be on the eastern edge of the higher heights, but it does look like we are likely to head into at least a short period of hotter and more humid conditions again starting Sunday. Highs in the low 90s with increasing humidity will likely mean 100+ heat index values for much of the area both Sunday and Monday.

AVIATION /18Z TAFS THROUGH 00Z THURSDAY/
Issued at 1228 PM CDT Tue Aug 4 2026

VFR flight conditions and light southerly flow is expected to prevail at least through this evening. May see isolated to widely scattered showers and thunderstorms develop ahead of a cold front late tonight across parts of central and northeast Missouri into west central Illinois. Storms late tonight into Wednesday morning are not expected to be particularly strong, although some could briefly reduce the visibility to 3SM and lower in heavy downpours. Another round of thunderstorms is expected Thursday afternoon.

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