SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0750 AM CDT Tue May 13 2025 Valid 131300Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE MID-ATLANTIC...NORTHERN GREAT PLAINS...AND DEEP SOUTH... ...SUMMARY... Isolated severe thunderstorms are possible: 1) today in vicinity of Virginia-North Carolina-West Virginia, 2) during the late afternoon to mid-evening over a portion of the Deep South, and 3) this evening into early morning Wednesday in parts of the northern Great Plains. ...NC/VA/WV vicinity... The upper-level low centered near the mid-Mississippi Valley will continue to lift east/northeast through tonight, as a notable shortwave trough rotates northeast across the Mid-Atlantic region. Generally weak surface-based instability (MLCAPE at or below 1000 J/kg) will exist across the coastal plain as a belt of stronger 850 mb flow lifts northeast across eastern sections of NC/VA. This will contribute to enlarged low-level hodograph structures and support the continued potential for transient areas of rotation and a few short-lived tornadoes associated with stronger convective elements. See recently issued Mesoscale Discussion 774 for details on short-term convective trends. Farther west into WV/western VA and NC, subtle large-scale forcing for ascent with the approaching upper low will contribute to thunderstorm development. Although deep-layer shear will tend to relax with westward extent, slightly more favorable mid-level lapse rates and 1000-locally 1500 J/kg MLCAPE will result in the potential for isolated strong/severe gusts and hail. ...AL/MS/TN vicinity... Some hi-res guidance continues to suggest a supercell or two may develop to the west of the departing mid-level trough, where a corridor of differential boundary-layer heating may support a favored zone for late afternoon through mid-evening storm development. Some veering of the wind profile should yield modest hodograph curvature. This, coupled with moderate mid-level west-northwesterly flow, will favor a conditional supercell threat. ...Northern Great Plains... An upstream upper-level trough over the western U.S. will move steadily east, resulting in strengthening southerly mid-level flow across the northern Plains. A Pacific cold front will make modest eastward progress today before becoming quasi-stationary across the western/central Dakotas, however the stronger mid-level flow will remain generally displaced to the west. Weak elevated buoyancy and sufficient deep-layer shear may still result in scattered storms, including supercells, with potential for severe hail. Some risk for strong/severe gusts may also exist with storms closer to the surface front. ..Bunting/Dean.. 05/13/2025