Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1215 PM CDT Sat Apr 22 2017 Valid 231200Z - 241200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SUNDAY ACROSS THE GEORGIA AND SOUTH CAROLINA PIEDMONT AND ADJACENT PORTIONS OF THE COASTAL PLAIN... ...SUMMARY... Thunderstorms impacting the Georgia and South Carolina piedmont and adjacent portions of the coastal plain Sunday may be accompanied by some risk for severe weather. ...Synopsis... The leading edge of a strong, zonal belt of westerlies (traversing much of the mid-latitude Pacific) appears likely to continue nosing inland across the Pacific coast, through the Great Basin and Rockies during this period. Models suggest that this may be accompanied by significant cyclogenesis within lee surface troughing near the Black Hills by Sunday night, as the southward progression of a cold front associated with a broad eastern Canadian upper vortex slows or stalls across the Upper Midwest and northern Plains. Despite these developments, substantive low-level moisture return to the Plains appears unlikely through this period and beyond, in the wake of a preceding cold front associated with a mid/upper perturbation digging into the Southeast. This latter feature may include a modest low embedded within larger-scale troughing, which is forecast to continue pivoting from a positive to neutral tilt as it progresses southeast of the lower Mississippi Valley, toward the south Atlantic Seaboard. While the associated front stalls to the lee of the southern Appalachians, and perhaps retreats northward near southern Mid Atlantic coastal areas by 12Z Monday, it is expected to continue advancing southeastward through the eastern Gulf states and central/eastern Gulf of Mexico. Although seasonably high moisture content air may tend to advect across and east northeast of the Florida peninsula and Bahamas, associated with an impulse within the subtropical westerlies, moisture near the Southeastern front and low is expected to contribute to sufficient destabilization for at least scattered thunderstorm activity. And models suggest an increasingly moist inflow off the western Atlantic into the Carolinas is possible by late Sunday night. Otherwise, mid-level cooling and steepening of lower/mid tropospheric lapse rates across the northern Great Basin and Rockies into parts of the north central Plains may be accompanied by widely scattered thunderstorm activity Sunday through Sunday night. ...Southeast... Models suggest that seasonably modest low-level moisture and lower/mid tropospheric lapse rates will yield generally weak CAPE (most unstable and mixed layer less than 1000 J/kg) along and south of the frontal zone. In the presence of 30-50 kt cyclonic lower/mid tropospheric flow, this might become sufficient to support scattered vigorous thunderstorm activity with at least some risk for hail and localized potentially damaging wind gusts Sunday afternoon and evening. It appears possible that convective potential could become maximized within a zone of stronger forcing for ascent, near those nose of stronger pre-frontal surface heating across the piedmont of northeastern Georgia, into the vicinity of the stalled frontal zone across the South Carolina piedmont, by late Sunday afternoon/evening. This may include a risk for organized convective development, including supercell structures. However, uncertainties remain too large for a forecast of severe probabilities any higher than 5 percent at this time. ..Kerr.. 04/22/2017Read more
from SPC Forecast Products http://ift.tt/ws9HZn
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