SPC AC 140538 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1238 AM CDT Fri Mar 14 2025 Valid 141200Z - 151200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS THE MID-MISSISSIPPI VALLEY AND PORTIONS OF THE LOWER OHIO VALLEY... ...SUMMARY... A regional outbreak of severe storms is likely across the Mid-Mississippi Valley to the Lower-Mississippi Valley, including portions of the Lower Ohio Valley. Tornadoes, several of which could be strong, widespread damaging winds with gusts from 70 to 90 mph, and scattered large hail up to baseball size will be possible. ...Discussion... Satellite imagery depicts a well-defined upper trough over the southwestern U.S./northwest Mexico. This feature is forecast to advance into the southern Rockies by sunrise as a 115kt 500mb speed max translates across southern NM. This jet max should increase to near 125kt as it translates into southwest OK by 18z, then weaken to near 100kt overnight over northern IL. Water-vapor/radar data suggest the leading edge of large-scale forcing is currently spreading across western NM. Latest model guidance suggests intense 12hr mid-level height falls (on the order of 240-270m) will spread across the southern Plains into IA as left-exit region of the aforementioned jet shifts into the mid-MS Valley. At the surface, a pronounced dry line will surge across the central Plains, arcing from a very deep surface low over northwest KS-eastern OK by 18z. Strong boundary-layer heating is forecast ahead of the cyclone, and convective temperatures will easily be breached as temperatures warm into the lower 70s. While surface dew points will remain a bit low, SBCAPE should exceed 1000 J/kg and robust convection will readily develop along the wind shift. Of particular concern will be the efficiency of mixing very strong flow downward within this convection. Forecast soundings exhibit 50kt just off the surface, and very steep lapse rates will prove favorable for severe gusts with any convection today. Widespread wind damage, with speeds likely exceeding 70 mph are expected. Severe squall line should organize and surge northeast across the mid-MS Valley during the afternoon/evening hours. Farther southeast, LLJ is forecast to strengthen markedly across eastern AR/MO into IL. This will allow somewhat higher boundary-layer moisture to advance across the lower into the middle MS Valley prior to thunderstorm development. Latest thinking is supercells should develop ahead of the fast-moving 500mb speed max, with some propensity for activity lingering across the mid-South as the right-entrance region of the jet influences longevity of convection. Forecast soundings strongly favor organized convection with supercells expected. Higher moisture content into eastern MO/southwest IL will contribute to higher tornado probabilities with these strongly sheared supercells. Longer-lived updrafts may produce strong tornadoes, in addition to very strong winds and large hail. Southern extent of the regional outbreak will likely be influenced by the lack of stronger forcing across the lower MS Valley. Even so, isolated severe supercells are expected within the less-forced environment. This activity may linger well into the overnight hours. ..Darrow/Moore.. 03/14/2025 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
Category: Watches, Warnings, Advisories, & Hazards