SPC May 18, 2017 0730 UTC Day 3 Severe Thunderstorm Outlook

By Newsroom America Feeds at 18 May 2017

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0224 AM CDT Thu May 18 2017 Valid 201200Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM SOUTHERN AND EASTERN TX INTO THE LOWER AND MIDDLE MS VALLEY AND LOWER OH VALLEY VICINITY... ...SUMMARY... Strong to possibly severe thunderstorms will be possible ahead of a cold front from southern and eastern Texas into the middle-to-lower Mississippi and lower Ohio Valleys. Hail and gusty winds will be the main concern with these storms Saturday and Saturday night. ...Synopsis... There is much uncertainty for the Day 3 period. The Plains upper trough will lift northeast to the Upper Midwest. Convection will be ongoing at the beginning of the period near a cold front from central TX into the mid-MS Valley. Guidance varies quite a bit in the location and track of a surface low somewhere in the vicinity of IA Saturday morning, creating uncertainty in a northward-advancing warm front across the Midwest and timing of the cold front. Across the warm sector, rich boundary-layer moisture will be in place, and where destabilization can occur, strong to severe thunderstorms will be possible across a large area from southern/eastern TX into the middle and lower MS and lower OH Valleys. ...Southern and Eastern TX to the Lower MS Valley... Forcing for ascent will be subtle across the region as the upper trough continue to pull away to the northeast. Guidance suggests some weak impulses may track across the area in southern-stream flow, but this is not well resolved at this time frame. Storms should be ongoing across parts of southwest TX near the cold front. Additional development is expected eastward along the cold front through the afternoon. Steep midlevel lapse rates will support a hail threat, though storm mode remains uncertain. If lines/bows occur, an attendant threat of strong winds could become the main concern. Given all of these uncertainties, will not introduce any higher severe probs at this time. Further east into the lower MS Valley, forcing and deep-layer shear will be weaker. Mainly diurnally driven convection is expected through the afternoon before the cold front moves into the region overnight. Gusty winds and hail could accompany these storms. ...Mid-MS and Lower OH Valley Vicinity... The severe threat is very uncertain across this region given expected convection ongoing during the morning. Where pockets of stronger instability materializes ahead of the cold front, some threat of strong to severe convection will exist. Hail and gusty winds will be the main concerns with any stronger storms that can develop. ..Leitman.. 05/18/2017 Read more



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