1PM Day 3 Convective Outlook for Friday, February 20. NO SEVERE THUNDERSTORM AREAS FORECAST
SUMMARY
Probabilities for severe storms Friday through Friday night appear less than 5 percent across the U.S.
Synopsis
Mid-level flow will remain strong and largely zonal over the southern US Day 3/Friday. A pronounced shortwave trough will move eastward toward the Atlantic Coast as subtropical ridging slowly builds over the Gulf Coast. A second low-amplitude trough over the Southwest will eject eastward and move into the Southeast early Saturday. A deep surface low associated with the first trough will occlude over the Great Lakes as its associated cold front continues to surge eastward across the upper OH valley. Trailing portions of the front will begin to stall across the Southeast and lower MS Valley Friday evening.
Lower MS Valley and Gulf Coast States
To the south of the strong southwesterly flow aloft, gradual moistening of the low-level air mass is likely Friday and Friday night along and south of the stalled front. While deep-layer ascent will be limited along the anticyclonic curved portion of the strong subtropical jet through much of the day, the approach of the secondary upper trough may support increased ascent late.
As mid/upper forcing for ascent moves eastward, it is expected to remain mostly to the cool side of the front. Some potential for stronger thunderstorm development seems likely to become focused along or just to the cool side of the frontal zone late Friday night into early Saturday. Low/mid-level lapse rates and buoyancy appear generally weak despite strong flow aloft. Model guidance also varies significantly on destabilization and moistening near the front. This, along with the late arrival of the stronger forcing suggests that while some stronger elevated storms are possible near the front, the risk is too conditional to introduce probabilities.
Upper OH Valley
As the surface low occludes, a strong cold front associated with the advancing upper trough will surge through portions of eastern OH and PA. A shallow line of weak convection is possible along the front owing to weak low-level moisture advection and strong ascent tied to the front. Largely devoid of meaningful buoyancy, little to no lightning is expected. Whoever, the presence of 100+ kt of mid-level flow could allow mixing of a few stronger wind gusts to the surface through the morning Friday. Minimal buoyancy and the lack of more robust moisture will preclude any severe probabilities.