SPC Feb 24, 2018 2000 UTC Day 1 Convective Outlook

By Newsroom America Feeds at 24 Feb 2018

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0153 PM CST Sat Feb 24 2018 Valid 242000Z - 251200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE ARKLATEX TO THE LOWER OHIO VALLEY... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST TEXAS TO PARTS OF THE OHIO VALLEY... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM CENTRAL TEXAS TO CENTRAL OHIO... ...SUMMARY... Severe thunderstorms capable of damaging winds and tornadoes will continue through tonight from the Arklatex east/northeastward through the lower Mississippi and lower/middle Ohio Valleys. Isolated strong tornadoes are possible. ...Discussion... No major changes have been made to the ongoing outlook, other than removing probabilities behind the eastward-advancing cold front. As a strongly forced band of thunderstorms progresses across Arkansas, it will encounter a thermodynamic environment increasingly favorable for damaging winds and tornadoes. Furthermore, recent KLZK VWP data sampled 0-1km SRH upwards of 500 m2/s2. In turn, bowing segments and related embedded circulations are likely to evolve within this line of storms, especially as they move through central Arkansas and approach the Mississippi Valley through this evening. ..Picca.. 02/24/2018 .PREV DISCUSSION... /ISSUED 0959 AM CST Sat Feb 24 2018/ Only minor changes have been made to the ongoing forecast. Morning surface analysis shows that the primary surface boundary currently extends from northeast TX to the MO Bootheel, then eastward into KY. A moist and increasingly unstable air mass is in place to the south of the boundary with dewpoints in the mid-upper 60s. The corridor along and just south of the boundary is expected to be the focus for severe storm activity this afternoon. 12z CAM solutions agree on development of intense storms around 17-18z over northeast TX/southwest AR, as strong large scale forcing overspreads the moist air mass. Considerable cloud cover will limit the degree of heating and destabilization today. However, forecast soundings in this area show substantial low-level helicity of 300-500 m2/s2 and sufficient CAPE for robust convection. Storm mode will likely be complex with discrete supercells transitioning to multiple bow/LEWP structures through the afternoon. CAPE/shear parameter ranges suggest the potential for a few strong tornadoes this afternoon across parts of AR and west TN. The risk of widespread damaging winds will also likely increase through the day as storm structures become more linear. The line of fast-moving severe storms is expected to sweep into parts of southern IN/central KY/middle TN after dark with a continued damaging wind and isolated tornado threat. Read more



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