Tuesday, August 27 – Afternoon Forecast
Tuesday Night: Isolated Storms Possible. Low: 74°F
Wednesday: Mostly Cloudy, Scattered Storms Possible. High: 94°F
Wednesday Night: Decreasing Clouds, Isolated Storms Possible. Low: 72°F
Thursday: Partly Cloudy. High: 95°F
Thursday Night: Increasing Clouds, Scattered Storm Chances. Low: 72°F
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General Discussion:
A heat advisory is in effect until 8 PM tonight (08/27/24). Spotty showers and storms will be possible tonight. These shower and storm chances will continue through Thursday. The heat we’ve been experiencing will continue to persist over the next couple of days.
-Jackson, Hayes, Schifferdecker
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Forecasters: Jackson, Hayes, Schifferdecker
Date Issued: 08/27/2024 6:00 PM CDT
Technical Discussion:
The GFS was used in combination with the NAM, although the NAM was more heavily relied on in this forecast. This is because the NAM more accurately represents the moisture content in the atmosphere.
At 250 mb, a large ridge is situated over the Midwest with a series of troughs embedded within the upper-level flow. This ridge has Missouri set in southerly flow, driving dewpoints into the low 70s. This combined with incoming solar radiation is what has caused the extreme heat this afternoon and will continue to keep temperatures above average over the next couple of days.
The focus this afternoon has shifted from extreme heat to isolated thunderstorms as activity has picked up throughout the afternoon. At 250 mb, divergence aloft is observed in central and northern Missouri starting at 00Z Wednesday within a shortwave trough. At 500 mb, pockets of vorticity can be seen propagating to the east from 00z-12z Wednesday within this shortwave, along with omega values of –10 to –15 µbar/s. Shear is not impressive by any means, but surface-based CAPE values have been in the 5000-6000 J/kg range as of Tuesday afternoon. These factors combined with the moisture in the upper levels of the atmosphere is what is causing the thunderstorms that have pulsed up throughout the afternoon. This shortwave will slowly move east throughout the evening, leaving scattered thunderstorms in the forecast until Wednesday morning. Since storms will not be widespread, and cloud cover will not be extensive, temperatures will be able to drop into the mid 70s by the end of the night.
Wednesday at 12z another shortwave is observed closer to northern Missouri. Pockets of vorticity along with omega values of –9 to –11 µbar/s encapsulating upper-level moisture will lead to more rain and thunderstorm chances from 12z-00z Wednesday. These factors will be held further up north, so rain chances will be harder to come by. However, moisture extending to the south throughout the day will lead to an increase in cloud cover. This increase in cloud cover is why temperatures will be slightly “cooler” in the mid 90s by the afternoon hours.
Thursday will be a bit more settled throughout the day as a slightly more zonal upper-level flow is expected over Missouri. A lack of moisture paired with this slightly more zonal flow will lead to partly cloudy conditions with temperatures in the mid 90s. Attention will be set more on the deep upper-level trough moving in from the northwest. A large line of vorticity, omega, and a temperature gradient that extends towards Missouri can be observed with this trough. This line begins to enter the state 06-09z Friday morning, and begins to become disorganized throughout the later hours of Friday morning. Future forecasting shifts should be aware of this deepening low and the timing of when impacts will arrive.
-Jackson, Hayes, Schifferdecker