Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1218 PM CDT Fri May 12 2017 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHEAST... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN THE BLACK HILLS VICINITY... ...SUMMARY... Isolated strong storms are possible across parts of the southeastern states Saturday. A few strong storms may also develop in the Black Hills vicinity. ...Southeast... 12/12z short-range model guidance continues to suggest an upper trough over the lower Mississippi Valley will dig east-southeast to a position over the central Gulf States, then off the Southeast Coast during the overnight hours. Westerly deep-layer flow is forecast to strengthen across the northeast Gulf Basin/northern FL early in the period in response to this evolution. Models are in general agreement that convection will be ongoing at the beginning of the period along a frontal zone that should be draped across the Carolinas into the FL Panhandle. While bulk shear will be strong across the warm sector, forecast lapse rates are marginal with values on the order of 6.5 C/km. As a result, buoyancy will be somewhat negated but adequate for organized frontal convection. This activity should advance across the southeastern states, with some upward evolution during the day due to diurnal heating, given the expected shear and large-scale forcing for ascent. At this time it appears isolated severe wind gusts will be the greatest risk, though marginally severe hail could accompany any supercells that manage to develop. ...Black Hills Vicinity... Large-scale height falls will spread across the northern Rockies during the day2 period as 500mb flow in excess of 60kt translates across the western half of MT/WY by 14/00z. Diffluent high-level flow will develop across the northern High Plains such that conditions will become increasingly favorable for convection despite marginal moisture/buoyancy. NAM guidance may be a bit too aggressive in surface dew points rising to near 50F but upper 40s should be sufficient for high-based convection ahead of approaching trough. Gusty winds and hail could be noted with the most robust convection that develops in the vicinity of the Black Hills from late afternoon into the evening hours. ..Darrow.. 05/12/2017Read more
from SPC Forecast Products http://ift.tt/ws9HZn
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