Marine Weather and Tide Forecast for Winchester, MO

SHORT TERM
(Through Late Thursday Night)
Issued at 156 PM CDT Wed Apr 23 2025

Quasi-zonal flow aloft will persist across a large portion of the CONUS east of the Rockies tonight with the passage of several shortwaves through the Nation's midsection. The most prominent trof will track well to our south across the lower MS Valley bringing high clouds to the region, while other weaker low- amplitude disturbances will track from central MO eastward this evening with another moving into central MO overnight. The western extent of surface ridging will be maintained across the area tonight resulting in largely east-southeast surface flow veering to weak southerly flow through the lowest few kms and this will allow for meager moisture return at best. As such any precipitation is expected to remain well west of the area with mild and dry conditions prevailing.

Heights aloft will be weakly rising on Thursday with flow becoming a bit more southwesterly in response to upstream amplification and a deepening upper trof moving into the West Coast. Several weak disturbances will traverse the region within the southwest flow aloft in the Thursday-Thursday night time frame. More uniform southerly low-level flow will ensue during this period as the last bit of surface ridging erodes and this will promote improving low- level moisture return and more instability, especially Thursday afternoon and night with the greatest concentration west of the MS River. In additional to above normal temperatures via the attendant WAA, this flow will support an increasing chance of showers and a few thunderstorms (isolated-scattered) starting tomorrow afternoon with the diurnal instability peak. The threat/coverage of precipitation is expected to increase Thursday night, especially across central/northeast MO into west-central IL in association with an increasing southwesterly LLJ and increasing larger scale forcing located ahead of an advancing cold front.

Glass

LONG TERM
(Friday through Next Wednesday)
Issued at 156 PM CDT Wed Apr 23 2025

The greatest threat/coverage of showers and thunderstorms should be centered on Friday and last into the evening in response to forcing with a cold front advancing across the CWA, and a migratory trof moving through the upper-mid MS Valley region.
Model projections of MLCAPE vary on Friday afternoon but generally range from 500-1000+ J/KG, and this will likely be modulated by ongoing precipitation and clouds limiting heating, while the ensemble guidance is showing the mean deep layer shear in the 20-25 kt range. This instability/shear spectrum would favor pulse or loosely organized multicell clusters, and it's not out of the question we could see a strong-severe storm where instability is locally maximized.

Cooler and drier weather will dominate on Saturday as weak northwest flow aloft prevails in the wake of the migratory upper trof and due to expansive post-frontal surface high pressure. Temperatures will be near to slightly below normal.

A pattern change will commence late Saturday into Sunday as a deep upper trof/low evolves over the western U.S. and an upper ridge builds and moves into the Mississippi Valley. A good warm-up will begin with this evolution as a low-level WAA regime gets underway Sunday and intensifies Monday with south-southwesterly lower tropospheric flow resulting in well above normal highs on Monday.
If we overachieve with warming, the 90th percentile of the NBM probabilistic temperature guidance would have Monday highs in record territory.

Eventually in the late Monday-Tuesday time frame the weakening western upper trof moves into the mid-upper MS Valley. There are differences in the LREF guidance with the upper trof location/structure and how amplified it is when in moves through the region. Ultimately this would impact the timing of the cold front passage and the overall shear profiles. That said, the mean LREF SBCAPE currently is in the 1000-1500 J/KG range (which is likely conservative) with the 75th percentile 1500-2000 J/KG, and mean deep layer shear 40-45 kts. This parameter space which would support potential for strong-severe thunderstorms with the advancing cold front which is highlighted in much of the machine learning guidance and the SPC DY7 Outlook.

Glass

AVIATION
(For the 00z TAFs through 00z Thursday Evening)
Issued at 623 PM CDT Wed Apr 23 2025

Dry and VFR conditions will persist through at least 18z Thursday.
A low (15-20% chance) for showers and thunderstorms begins to materialize in central Missouri in the 20z-00z timeframe and in the St. Louis metropolitan area in the 02z-06z timeframe. That said, confidence on convection impacting areas near the terminals is currently low and thus PROB30s were not included in these TAFs.
Winds will remain generally light out of the south through the TAF period outside of any convection.

MRB

CLIMATE
Issued at 218 AM CDT Wed Apr 23 2025

Unseasonably warm temperatures are expected on Monday, nearing daily records for late April. Here are the daily record highs for April 28.

LOCATION RECORD ST LOUIS 92 set in 1970 COLUMBIA 88 set in 1970 QUINCY 88 set in 1970



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