Heavy to excessive rainfall may lead to flooding today over southwest Pennsylvania into northern West Virginia, and western Maryland. Severe thunderstorms are possible this afternoon and evening in the Mid-South and across Eastern North Carolina. An extended period of hot weather is forecast for parts of coastal southern California including Los Angeles from today through Thursday. Read More >
Event Summary |
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An upper-level low pressure system moved into the Ohio Valley on Friday morning, gradually devolving into an open wave by the evening hours as it shifted into the Central/Southern Appalachians. This storm system brought some stronger wind shear and jet energy into the Tennessee Valley, than what is typically observed for mid to late June in Alabama. Additionally, a very moist air mass was in place further south of this low pressure area, where a pre-frontal trough axis extended southwest into across portions of Middle Tennessee into Northwest Alabama. This moist, unstable air mas created an environment favorable for more intense, organized strong to severe thunderstorms capable of damaging winds and a few isolated tornadoes. |
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As heating occurred during the morning hours on Friday, instability values increased significantly by early afternoon, and strong to severe thunderstorms developed along near and ahead of this pre-frontal boundary (especially near and north of the AL/TN border). This thunderstorm activity produced damaging winds, small hail, and frequent lightning. |
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Later in the evening, the primary surface cold front sagged southeast temporarily into northern Alabama, before lifting back to the northwest late Friday evening. This feature served as a focus for severe thunderstorms, locally increased wind shear and helicity values. These conditions, combined with a moderately unstable environment present, helped produce additional severe thunderstorms Friday evening and assisted in the process of tornadogenesis. A strong EF-2 tornado was documented in Cullman County and an EF-1 tornado was documented in Jackson and DeKalb Counties. |
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