Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1030 AM CST Tue Jan 03 2017 Valid 031630Z - 041200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are possible today over parts of the Ohio Valley region, as well as from the eastern Carolinas to northern Florida. Some thunder potential may extend into tonight over parts of peninsular Florida. ...Synopsis... In mid/upper levels, a zonal to subtly cyclonic flow field prevails over most of the contiguous U.S., with three predominant perturbations: 1. The shortwave trough associated with yesterday's severe weather, initially located from WV to the Carolinas, is expected to eject northeastward over the coastal Mid-Atlantic and New England through the remainder of the period. 2. A weak 500-mb low currently near the Northwest Angle of Minnesota, with shortwave trough southwestward over the Dakotas, is expected to move eastward to the Thunder Bay region, while faster translation of the basal vorticity lobe and speed max lead to increasing negative tilt of the height trough. This process, along with broader amplification to large-scale troughing over eastern North America, will contribute to gradual height falls through the period over most of the eastern U.S. 3. A positively tilted trough exists from the northern Rockies across the Columbia Gorge area to the Pacific, with an embedded low now evident in moisture-channel imagery just offshore from OR. Evolution and expansion of the offshore cyclone is forecast with the low moving slowly eastward toward the OR coast by tomorrow morning. At the surface, an occluded low over OH will move northeastward and continue to weaken, as another weak low now near the Hampton Roads region becomes better-defined and moves northeastward up the coast and across the Cape Cod region. An initial surface cold front, now trailing southwestward from the low across the Carolinas, GA and the FL Panhandle, will move slowly southeastward across northern FL through the period, while a reinforcing arctic front moves southeastward across the remainder of TX and the lower Mississippi Valley. ...Southeast... Isolated to widely scattered thunderstorms remain possible along and ahead of the leading surface cold front from the coastal plain of the Carolinas and GA across the coastal bend and northern peninsular areas of FL. Favorable low-level moisture and pockets of diabatic surface heating, along with weak but adequate low-level convergence and lack of substantial MLCINH, will support this convection. Sufficient deep shear and SRH still are evident to support transient storm-scale rotation. However weak lapse rates will mitigate updraft strength, and veering boundary-layer flow with time is expected with the departure of the mid/upper trough away from the region. The latter will lead to a diminishing trend with time of both vertical shear and low-level convergence. While a strong storm cannot be ruled out within this belt during the next few hours, the potential for organized severe has become too isolated and conditional to maintain severe probabilities at categorical levels. ...Ohio Valley... A more subtle mid/upper-level shortwave perturbation, following closely behind trough #1 above, is evident at this time over the mid Mississippi Valley/lowest Ohio Valley area, and will contribute sufficient destabilization in midlevels to support widely scattered elevated convection with isolated embedded thunder today. Isolated lightning has been detected upstream over central IL during the past half hour in somewhat more meager instability. Forecast soundings suggest supportive parcels will be lifted within saturated zones in the 600-800-mb layer, with MUCAPE only in the 50-200 J/kg range. While additional isolated thunder cannot be ruled out off the margins of this outlook area, the best potential for coverage at least 10% has changed little since the last forecast. ..Edwards/Darrow.. 01/03/2017Read more
from SPC Forecast Products http://ift.tt/wWCv9s
No comments:
Post a Comment