Tuesday Night: Cloudy with slight rain possible. Low: 54°F

Wednesday: Partly cloudy. High: 73°F

Wednesday Night: Clouds clearing. Low 55°F

Thursday: Increasing clouds. High: 77°F

Thursday Night: Mostly cloudy. Low: 58°F

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General Discussion:

Cooler weather persists as a cold front makes its way from the north, bringing cloud cover and chances for slight rain (>.1 in) overnight into Wednesday morning. We gain a slight break from cloud coverage Wednesday night, before increasing clouds from the southeast move into south and central Missouri Thursday, persisting into the weekend. Temperatures will linger below average (81°F) for the forecast period.

– Hayes

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Forecasters: Hayes, Jackson, Schifferdecker

Date Issued: 09/24/2024 5:00 P.M.

Technical Discussion:

Key Messages:

• Cloud coverage and below average temperatures, (mid to low 70s), will continue throughout the work week.
• The low pressure system cascading down Missouri will be wrapping back around Thursday night into Friday morning due to Tropical Storm Helene.

The GFS and NAM forecasting models were used to compose this forecast, for their display on future weather patterns for this week. 

A deep upper-level trough makes its way down from the North, turning the positively-tilted low into a cut-off low once reaching southern Missouri and northern Arkansas Thursday morning (06:00Z). Counter-clockwise vertical vorticity at 500MB follows the motion of the trough, before subsequently being cut-off from the upper-level flow. This low then lingers in the south to be later emboldened by Tropical Storm Helene which will make landfall Early Friday around (03:00Z). Surface level precipitation accumulation as well as Skew-T imagery describes lack-luster moisture present Tuesday night into Wednesday morning as the trough passes over Missouri, creating a chance for slight rain, (<.1 In),  to occur. Clouds hovering above central Missouri during the day Wednesday begin to move eastward by the evening, (21:00Z), shifting moisture southeast of the area. This movement in cloud coverage will allow temperatures a chance to increase from earlier weekday highs.

Clouds decrease Thursday as the cut-off low dips to the south and an easterly wind takes its place, yet by 18:00Z, Low to mid-level RH suggests an increase in moisture returning to the area. At 300 MB, models indicate an increase in divergence aloft as well as an increase in relative humidity approaching Thursday night over central Missouri. Mid-level vertical vorticity spawning from the southern low shifts over southern Missouri as the low becomes intertwined with the Tropical Storm Helene. This combination of the cut-off low and tropical storm may provide chances for more turbulent weather as it tracks a path from the gulf upwards, creating more pockets of divergence and shoving moisture back towards Southern and central Missouri. Future forecasts may be impacted by the strengthening of the upper-level trough and should monitor the evolution and potential impact of this system.

• Hayes, Schifferdecker, Jackson