SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1258 AM CDT Mon Apr 14 2025 Valid 141200Z - 151200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE OHIO VALLEY...CENTRAL APPALACHIANS AND MID-ATLANTIC... ...SUMMARY... Scattered strong to severe storms are expected this afternoon and evening across parts of the Upper Ohio Valley eastward to the Mid-Atlantic. Large hail, severe wind gusts, and a tornado threat will be possible. ...Lower Ohio Valley/Central Appalachians/Mid-Atlantic... At mid-levels, a positively-tilted trough will move through the northern Plains as a low moves northeastward into Ontario. Heights will fall today from the Ohio Valley into the Northeast as a ridge moves into the western Atlantic. At the surface, a pre-frontal trough will develop in the lee of the Appalachians, as a cold front advances southeastward through the lower Ohio and mid Mississippi Valleys. Ahead of the front, low-level moisture will advect northeastward into Kentucky, southern Ohio and West Virginia. As instability increases along this corridor, scattered thunderstorms are expected to develop during the afternoon from near the front eastward along the northern edge of the instability gradient. Multiple relatively small clusters of storms are expected to form and move eastward into the central Appalachians. An 80 to 90 knot mid-level jet will move across the central Plains today, as the exit region of the jet overspreads the Ohio Valley. Lift and strong deep-layer shear associated with the exit region of the jet will support strong to severe thunderstorm development this afternoon. Forecast soundings this afternoon from eastern Kentucky into West Virginia have MLCAPE peaking near 2000 J/kg with 0-6 km shear in the 60 to 65 knot range. This will support a severe threat, associated with isolated supercells and short bowing line segments. Large hail will be most likely with supercells. In addition, low-level flow is forecast to steadily increase in the late afternoon and early evening near the moist axis. This will create strong low-level shear favorable for a tornado threat. The tornado threat is expected to be the greatest from far northeast Kentucky into parts of West Virginia, where 0-3 km storm-relative helicity is forecast to reach the 200 to 350 m2/s2 range. Supercells and short bowing line segments will also be capable of producing wind damage. During the early to mid evening, the severe threat is expected to spread eastward into the Mid-Atlantic, where severe gusts and isolated large hail will also be possible. ..Broyles/Wendt.. 04/14/2025