Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0747 AM CDT Sat Mar 25 2017 Valid 251300Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF MS/AL/LA... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS MID-MS VALLEY TO THE GULF COAST STATES... ...SUMMARY... Isolated to scattered damaging winds may accompany a line of thunderstorms shifting east from Louisiana and Mississippi into Alabama through this afternoon. ...Synopsis... Stacked synoptic cyclone over the Ozark Plateau will drift towards the Mid-MS Valley through early Sunday. Mid-level trough axis which extends south to the western Gulf Coast should reach AL/FL. Surface cold front across the Sabine Valley will push into the Lower MS Valley this afternoon before undergoing frontolysis tonight. ....MS/LA/AL... A slowly weakening pre-frontal squall line is ongoing from northeast MS through southeast LA, with a cluster of storms along the cold front in far southeast TX. Extensive convective overturning along with further development of convection across the Sabine Valley will substantially limit warm-sector buoyancy ahead of the front as it approaches the Lower MS Valley. The primary severe risk should remain along/ahead of the pre-frontal squall line as diurnal destabilization occurs. However, boundary-layer moisture will be modest north of the central Gulf Coastal Plain, yielding only weak buoyancy. Low/mid-level wind fields east of the mid-level trough axis will further decay today, but effective shear values around 30-35 kt could support some risk for strong wind gusts, especially if the Sabine Valley cluster can merge with the remnant pre-frontal line near the central Gulf Coast. The composite squall line should weaken in the evening as it reaches eastern AL to the FL Panhandle. ...Mid-MS Valley... Presence of only lower to middle 50s surface dew points along with extensive convective overturning farther south in the warm sector should hamper development of MLCAPE beyond about 500 J/kg with only moderate mid-level lapse rates within the cold core region. Moderate deep-layer shear should support a few transient, weakly rotating updrafts. This may prove adequate for a marginal severe hail and locally damaging wind risk, mainly this afternoon. ..Grams/Dial.. 03/25/2017Read more
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