Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0734 AM CDT Wed Jun 07 2017 Valid 071300Z - 081200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE HIGH PLAINS AND VICINITY...AND EAST ACROSS THE MID MISSOURI AND UPPER MISSISSIPPI VALLEYS... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE FLORIDA PENINSULA... ...SUMMARY... Isolated severe thunderstorms will be possible today into tonight across portions of the Front Range of the Rockies and High Plains to portions of the upper Mississippi Valley, and across portions of Florida. ...Synopsis... A large upper low is progged to remain off the western North America coast, though lead impulses embedded within the broad cyclonic flow field surrounding the low will increasingly affect northern California and the Pacific Northwest. Downstream, ridging aloft will persist across the Rockies and into the Plains, though several small-scale vorticity maxima -- the strongest of which is indicated over the northeast North Dakota vicinity this morning -- will continue moving through the anticyclonic flow around the ridge. Finally, an upper low is forecast to strengthen with time over the central Appalachians vicinity, within a broader, positively tilted trough gradually shifting southeast across the northeastern states. Farther south, a broad/fairly weak upper low now near the Florida Peninsula will continue moving slowly east through the period. At the surface, a weak cool front is forecast to move slowly southeast across the northern Plains, while a lee trough remains over the high Plains. In the southeast, a baroclinic zone will remain aligned east-northeast to west-southwest from off the southern Atlantic Coast into the northern Gulf of Mexico, making only minimal southeast progress through the period. ...Northern Intermountain region and high Plains east across the mid Missouri Valley to the upper Mississippi Valley... Diurnal diabatic heating of a modestly moist (by late spring standards) boundary layer (dewpoints only in the 50s to near 60 anticipated this afternoon), will result in modest afternoon CAPE development near the north central U.S. cool front, and across the high Plains region westward into southern Montana. The resulting CAPE increase will be sufficient to fuel scattered to isolated storm development -- along both the cool front and near higher terrain from southern Montana southeastward and southward across the front range of Colorado and New Mexico. With time, storms will spread southeast across the high Plains, steered by moderate (20 to 25 kt) northwest flow aloft. Overall, relatively weak shear should limit overall storm organization/severe risk, and thus will maintain only 5% probability for wind/hail. Storms -- both along the front as well as over the high Plains area -- will generally diminish into the evening in conjunction with cooling of the boundary layer, but may linger within one or two small/southeastward-moving clusters through a good part of the evening. ...The Florida Peninsula... Gradual eastward advancement of the upper system over the northeastern Gulf of Mexico will support continued areas of scattered to widespread showers and thunderstorms across the southeast U.S. today. Band of persistent/enhanced southwesterly flow aloft on the eastern fringe of the upper system will remain atop the Florida Peninsula. As such, despite ongoing clouds/precipitation and thus limited potential for diurnal heating/destabilization in most areas, potential exists for locally enhanced convection, and possible/associated risk for a few stronger gusts through the period. ..Goss/Dial.. 06/07/2017Read more
from SPC Forecast Products http://ift.tt/rATNzD
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