SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 PM CDT Sat Aug 21 2021 Valid 220100Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN PLAINS...TENNESSEE VALLEY...SOUTH CAROLINA AND INTERMOUNTAIN WEST... ...SUMMARY... Marginally severe thunderstorms are possible this evening across parts of the southern Plains, Tennessee Valley, South Carolina and the Intermountain West ...Southern Plains... The latest water vapor imagery shows an upper-level ridge over the western Ozarks, with a plume of mid-level moisture extending northeastward from west Texas into western Oklahoma. Scattered thunderstorms are ongoing within this plume. The storms are located along the west and north side of a pocket of strong instability according to the RAP. Although deep-layer shear is relatively weak, low-level lapse rates are steep. This could be enough for a marginal wind damage threat early this evening. The strong instability also could be enough for hail with the better organized updrafts. ...Tennessee Valley... The latest water vapor imagery shows northwest mid-level flow in place from the mid Mississippi Valley into the Southeast. A corridor of maximized instability is present from southern Arkansas into middle Tennessee where surface dewpoints are mostly in the 70s F. This is contributing to moderate instability according to the RAP. Although deep-layer shear is only around 20 kts, low-level lapse rates are steep. This could be enough for a marginal wind damage threat over the next hour with storms located in the stronger instability. ...South Carolina... An upper-level low is currently analyzed in parts of the central Appalachians. The airmass beneath the low is moist with surface dewpoints generally ranging from the upper 60s in the higher terrain to the mid 70s F over the Atlantic coastal Plains. The strongest instability is located across southern South Carolina where the RAP is estimating MLCAPE in the 2000 to 2500 J/kg range. This combined with 20 to 25 kt of deep-layer shear and steep low-level lapse rates will make strong wind gusts possible over the next hour. ...Intermountain West... The latest water vapor imagery shows an upper-level trough over the Intermountain West. Ahead of the trough, a pocket of instability is present from northern Utah into southwest Wyoming. Although instability is weak across the Intermountain West, regional WSR-88D VWPs suggest that 0-6 km shear is in the 40 to 50 kt range. This could be enough to enable a few storms to reach marginally severe criteria. Damaging winds and hail are the primary threats. ..Broyles.. 08/22/2021 Read more LIVE: spc.noaa.gov
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