Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1108 AM CDT Sat Jul 22 2017 Valid 221630Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OH VALLEY TO MID-ATLANTIC... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS UPPER MIDWEST... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE SLIGHT RISKS TO THE CENTRAL GREAT PLAINS... ...SUMMARY... Scattered wind damage is possible from parts of the Ohio Valley eastward into the Mid-Atlantic through this evening, with scattered severe hail possible across parts of the Upper Midwest late this afternoon and evening. ...Mid-Atlantic States... A lead MCV is progressing east across northwest PA with a short convective line segment farther south across the MD/eastern WV Panhandles. Surface wind gusts with this leading-line convection have remained modest amid a minimal cold pool. Robust diabatic heating downstream across the Piedmont and Coastal Plain should result in convection expanding in coverage and intensifying during mid/late afternoon. With area RAOBs sampling 700-500 mb lapse rates of 5.5-6.0 degree C/km, setup should favor damaging winds as the main hazard. On the periphery of 700-mb winds at or above 30 kt along with an ill-defined surface pattern, wind damage should primarily be produced by scattered strong wind gusts. ...OH Valley/Midwest... Primary change this outlook is to expand Slight Risk west. Destabilization is well underway with south to southwest surface winds in the wake of leading-line convection over the central Appalachians. More pronounced outflow has been established from decaying convection over east-central IL and this should mark the western edge of organized severe potential. Weak confluence boundaries and low-level WAA atop the remnant outflow across parts of southern IL/IN/OH should aid in multiple rounds of scattered storms through this evening. Large buoyancy to the south amid a swath of 30-40 kt 700-mb flow will offer a primary risk of damaging winds and secondary risk of severe hail. ...Upper Midwest... A compact shortwave trough over southern MB should reach Lake Superior tonight. Widely scattered storms are expected downstream and south of this trough first across northern MN and later into WI. A nearly unidirectional mid/upper-level profile with robust speed shear will favor elongated hodographs supportive of splitting supercells. Overall intensity should be stymied by ongoing light northerly surface winds and swaths of stratus evident from the MN Arrowhead into southern WI. But on the northeastern periphery of an air mass that should become moderately unstable, the setup should yield risks of severe hail and locally damaging winds. ..Grams/Bunting.. 07/22/2017Read more
from SPC Forecast Products http://ift.tt/wWCv9s
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