Thursday Evening Forecast 09/26/2024

Thursday Night: Mostly cloudy, slight chance for showers. Low: 60°F
Friday: Mostly cloudy, chance of AM showers. High: 72°F
Friday Night: Mostly cloudy. Low: 61°F
Saturday: Partly sunny. High: 76°F
Saturday Night: Partly cloudy. Low: 60°F
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General Discussion:
Major hurricane Helene approaches landfall bringing humid air and scattered showers throughout the eastern Midwest and Southeast regions. Cloud cover increases throughout the weekend due to moisture advection pushing up from the Gulf, but Northwestern parts of the state will be left dry as high pressure approaches from the West. – Daniel, Franciscus
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Forecasters: Daniel, Nightingale, Franciscus
Date Issued: 09/26/2024 5:00 PM CDT
Technical Discussion:
Key Messages:

• Low pressure systems approach as cloud cover increases rapidly in the surrounding areas.
• Ridging to the west of Missouri helps prevent the active weather involved with the hurricane, leaving us with warmer, dry air.

Major hurricane Helene approaches the Big Bend of Florida overnight bringing low pressure throughout the Southeastern United States. A preexisting low pressure in the southeastern Midwest region will merge with the hurricane overnight Thursday causing a Fujiwara effect. Increased cloud coverage in the upper-levels is possible bringing precipitation and strong winds up to 80kts at 300mb. A steady Northwesterly flow settles toward the end of the forecast period along with light showers Sunday morning.

As the Fujiwara effect takes place throughout the forecast period, levels of vorticity increase around the low pressure systems as they merge in the mid-levels. Persistent conditions remain throughout the weekend with possible showers Friday night through Sunday morning. Ridging to the West prevents the cyclone from reaching parts of Mid-Missouri as well as areas further northwest.

Lower-level relative humidity in Columbia increases to levels between 50-60% as Helene makes landfall. Cold air advection will continue to prevent cloud cover overnight Thursday while Friday morning coverage is expected. Coverage increases throughout the day and into Saturday.

Closer to the surface, ridging to the West continues to push low pressure into the Tennessee valley and away from Mid-Missouri. An impressive low-level jet out of the Northeast brings cooler air and stronger winds up to 40kts at 850mb into Friday morning and weakens Saturday afternoon and evening as the low spins off into the East. Future forecasters should be aware of a trough to the North within the upper level jet stream.

Daniel, Franciscus