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Archives for the SPC Convective Outlook are updated daily (approximately) with a live map at the beginning of each article. Follow the link at the end of the article to check for current updates on the NOAA/NWS Storm Prediction Center website. Also, see Archives for Chicago's hourly weather data on CARDINAL NEWS Magazine.


Saturday, August 21, 2021

SPC Aug 21, 2021 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1253 AM CDT Sat Aug 21 2021 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN PLAINS...ARKANSAS RIVER VALLEY...SOUTHEAST AND INTERMOUNTAIN WEST... ...SUMMARY... Isolated severe thunderstorms may produce locally damaging wind gusts across parts of the southern Plains, Arkansas River Valley and Southeast. A few strong wind gusts could also occur across parts of the Intermountain West. ...Southern Plains/Arkansas River Valley/Southeast... Heights will rise within an upper-level ridge today located from the Arklatex into the western Ozarks. At the surface, a moist airmass will be in place from parts of the southern Plains eastward into the lower to mid Mississippi Valley. By afternoon, a east-to-west corridor of moderate to strong instability is forecast across northern Oklahoma, north-central Arkansas and northern Mississippi. An outflow boundary associated with an overnight MCS should be positioned from northern Oklahoma into northern Arkansas. Thunderstorm development will be likely along and near this outflow boundary during the late afternoon. Although deep-layer shear should be relatively weak from the southern Plains into the lower to mid Mississippi Valley, low-level lapse rates will become steep during the late afternoon. For this reason, the stronger multicells could produce isolated damaging winds. Further to the west, from northwest Oklahoma into the Texas and Oklahoma Panhandles, thunderstorms are also expected to develop along the western end of a corridor of moderate instability. Forecast soundings by 00Z/Sunday suggest that steep lapse rates will be present in the low to mid-levels. This could be enough for hail, in addition to a wind-damage threat. ...Intermountain West... An upper-level trough will move eastward across Pacific coastal states today, with southwest mid-level flow located in much of the Intermountain West. Ahead of the trough, a southwest-to-northeast corridor of instability is forecast to develop from northeast Nevada across northern Utah and into southwest Wyoming. As surface temperatures warm along this corridor of instability, convection should develop during the afternoon. Although instability should remain relatively weak, forecast soundings in northern Utah late this afternoon suggest that 0-6 km shear will be around 40 kt. This combined with 0-3 km lapse rates near 9.0 C/km should be favorable for isolated strong wind gusts. ..Broyles/Karstens.. 08/21/2021 Read more LIVE:
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