Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1148 PM CST Sun Dec 25 2016 Valid 261200Z - 271200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF SOUTHWESTERN AR NORTHEASTWARD INTO THE MO BOOTHEEL... ...SUMMARY... Isolated strong to locally severe thunderstorms may occur across mainly portions of Arkansas this afternoon. ...Synopsis... A potent mid-level low and associated shortwave trough will move across parts of southeastern Canada and Great Lakes and into the Northeast U.S. while a split-flow regime impinges on the West Coast. A cold front over the Great Lakes and Ohio Valley will progress eastward today and tonight while the southern portion of the front --partially modulated by convective activity-- very slowly moves eastward across northern parts of the Lower MS Valley and ArkLaTex regions. Isolated to widely scattered showers and isolated storms will preferentially be located near the front where lift will focus. Meager buoyancy will conditionally support a few lightning flashes with deeper convection on the northern portion of the front over the OH Valley. However, forecast soundings indicate updrafts will be elevated, thereby limiting storm intensity. ...AR... A slow eastward movement of the front is forecast from the lower OH Valley southwestward into the ArkLaTex region today. Low-level moisture will continue to gradually increase ahead of the front within a broad zone of weak warm air advection/confluent flow. Surface observations late Sunday night show a plume of 65-70 degree F dewpoints over the Sabine River valley and this increase in moisture coupled with modest diurnal heating is expected to yield 500-1000 J/kg MLCAPE by early afternoon. Tropospheric flow largely parallel to the front may act as a limiting factor for semi-discrete storms to develop. However, a general glancing influence and weak forcing for ascent --neutral mid-level height tendency-- associated with the upper system over the Great Lakes may yield a window of opportunity for storms to intensify during the afternoon. The southern fringe of stronger westerlies and moderately strong and veering low-level flow will support some risk for transient updraft rotation with the stronger storms. Widely scattered to scattered storms will probably peak both in coverage and intensity during the afternoon. The strongest storms potentially could result in a localized damaging wind/tornado risk before this activity weakens during the evening. ..Smith/Bunting.. 12/26/2016Read more
from SPC Forecast Products http://ift.tt/s7Jkvo
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