SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 AM CDT Fri May 28 2021 Valid 281300Z - 291200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS WEST TO CENTRAL TX AND EASTERN NM... ...SUMMARY... Scattered severe thunderstorms with very large hail, damaging winds, and a couple tornadoes are possible across parts of west and central Texas into eastern New Mexico, mainly this afternoon and evening. ...TX and eastern NM... Elevated convection rooted along the low-level baroclinic zone in northwest TX may pose a risk for isolated severe hail and strong wind gusts this morning. To the southeast of this activity, a separate area of thunderstorm development is expected towards midday near the Big Country/Concho Valley vicinity as convergence strengthens along the remnant outflow boundary from decaying convection over east TX. Scattered thunderstorms should also develop across the higher terrain of eastern NM and the TX Trans-Pecos during the afternoon. A plume of moderate to large buoyancy is expected along and south of the composite front/outflow with peak MLCAPE of 3000-3500 J/kg in the Edwards Plateau to Permian Basin vicinity of west TX. With a belt of 30-40 kt 500-mb westerlies atop weak low-level easterlies, a nearly straight-line hodograph should foster left and right-splitting supercells capable of producing very large hail. Some guidance such as the HRRR indicates potential for numerous supercells across the region by late afternoon which should evolve into multiple east-southeast propagating clusters this evening, aiding in an increasing severe wind threat as well. For these reasons, have expanded the cat 2/SLGT risk. Greatest tornado potential will probably be maximized along a narrow portion of the baroclinic zone across the Permian Basin if a discrete supercell is able to be sustained off the Sacramento Mountains, with spatial extent likely limited by increasing MLCIN deeper into the post-frontal air mass. ...Deep South to OH Valley to the Lower Mid-Atlantic... Ahead of convective outflow associated with decaying convection across the Deep South to TN Valley and within a broad low-level moist advection regime, weak surface-based buoyancy is expected this afternoon. The most deeply mixed boundary layer is expected farther east along the South Atlantic Coastal Plain where buoyancy should be lacking due to a hot but dry air mass. Forcing for ascent should be greatest across a portion of the OH Valley towards the central Appalachians downstream of a shortwave trough moving east over the Midwest. But confidence is low that appreciable destabilization will occur here given pervasive morning cloud coverage. A separate corridor of ascent may be focused near a diurnally strengthening surface cyclone in south-central to southeast VA. Vast differences in the degree of destabilization among guidance amid poor mid-level lapse rates in regional 12Z soundings render low confidence in a greater damaging wind threat here relative to the rest of the lower-end severe risk. Still, a brief tornado and locally damaging winds are possible along the warm front from southeast VA into southern MD. ...Northeast WY/southeast MT... Within a weakly buoyant but amply sheared environment, a couple discrete supercells may develop off the Big Horns during the late afternoon to early evening. Here, weak mid-level height falls downstream of a Northwest short wave trough will be favorably timed with peak diurnal heating. Isolated large hail and severe wind gusts are possible until convection weakens upon encountering a more stable air mass in the western Dakotas. ..Grams/Gleason.. 05/28/2021 Read more LIVE: spc.noaa.gov
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