Weather Talk: Unknown high conditions can create strong thunderstorms
Last Saturday night, there was an outbreak of very strong thunderstorms in and around our area following a very humid day with temperatures in the 90s. The thunderstorms happened during the overnight hours and not during the peak heating period of the late afternoon.
For most of the day, upper level winds were quite weak over our region. Although the air was moist and unstable, there was no trigger – nothing to set off any storms. During the evening, an approaching region of cooler temperatures and stronger wind speeds in the upper atmosphere approached. As the upper level temperatures cooled and wind increased, it remained warm and humid near the surface. This created a much more favorable environment for storms even though the surface temperatures had cooled considerably since the early evening.
Northern Plains thunderstorms are often 50,000 to 60,000 feet tall, and it is often the conditions high up that we cannot sense directly that make storms strong.
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