Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0307 AM CDT Tue Jun 20 2017 Valid 221200Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS EXTENDING FROM THE CENTRAL HIGH PLAINS THROUGH IOWA TO SOUTHERN WISCONSIN...NORTHERN ILLINOIS...FAR NORTHWEST INDIANA...AND SOUTHWEST LOWER MICHIGAN... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE SLIGHT RISK AREA FROM PORTIONS OF THE CENTRAL AND SOUTHERN HIGH PLAINS TO THE SOUTHERN GREAT LAKES... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE LOWER MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms are expected Thursday afternoon into Thursday night across portions of the southern Great Lakes through Iowa, Nebraska, northern and western Kansas into portions of the central and southern High Plains. Meanwhile, a tornado threat and potential for damaging winds will be possible across the lower Mississippi Valley region as the remnants of Potential Tropical Cyclone Three advance inland. ...Synopsis... A positively tilted long-wave trough, anchored by a closed low moving east across northern Ontario, will advance into the northwest to north-central tier of states. Strongest midlevel flow will remain across the northern tier of the contiguous United States. A cold front will advance east across the upper Great Lakes and should merge with a warm front in Lower Michigan Thursday night. The trailing portion of the cold front will advance south through the upper MS Valley and the central Plains, with a lee trough extending south through the central High Plains. For information about Potential Tropical Cyclone Three, please refer to NHC for latest guidance. This tropical system should be moving inland across the northwest Gulf Coast region this forecast period. ...Southern Great Lakes through IA and the central Plains... Thunderstorms, some possibly severe, are expected to be ongoing at 12Z Thursday across parts of SD and possibly into the upper Great Lakes region. The combination of differential heating boundaries along mainly the southern periphery of this early period convection and the cold front are expected to be the primary foci for afternoon into evening thunderstorm development. Gradual height falls atop the cold front is expected to prove favorable for thunderstorm development along much of the cold front as it moves into a moderately unstable environment. Westerly shear vectors oriented parallel to the surface boundaries and combined with the moderate destabilization will support organized strong to severe storms, with line segments and supercells possible. Farther west, the CAPE/shear parameter space within a deeply mixed boundary layer across NE into the central and southern High Plains will result in large hail, some very large, and damaging winds as the primary severe-weather threats. ...LA/MS/southern AR/far eastern TX... Pockets of instability and favorable low-level shear should allow for both a marginal severe-weather threat for damaging winds and a few tornadoes as the tropical system moves inland. Although the NHC guidance suggests a weakening cyclone, guidance suggests strengthening southerly low-level winds in the eastern quadrant across LA into southern AR Thursday night. If this occurs, there would be a continued risk for isolated damaging winds, and perhaps a tornado threat through late in the forecast period. ..Peters.. 06/20/2017Read more
from SPC Forecast Products http://ift.tt/GAMjPN
No comments:
Post a Comment