Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0146 PM CST Mon Jan 16 2017 Valid 162000Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE ARKLATEX AND MID MISSISSIPPI RIVER VALLEY... ...SUMMARY... A few strong to severe thunderstorms remain possible this afternoon and early evening from the Arklatex region to the Mid Mississippi Valley. Strong to locally damaging winds, a brief tornado, and small to marginally severe hail are possible on an isolated basis. ...20Z Update... No appreciable changes have been made to the prior outlook. Latest visible satellite trends indicate cumulus building along a cold front from MO southwestward into east TX, and isolated to scattered convection is forecast to occur across this region. Modest diurnal heating has allowed surface temperatures to warm into the 50s north to upper 60s/mid 70s south. Weak instability amidst sufficient bulk shear across the Arklatex and mid MS Valley should support an isolated threat for strong to locally damaging wind gusts, a brief tornado, and perhaps some hail through the early evening hours. The loss of diurnal heating later this evening should temper the marginal severe risk as instability weakens and the prospect for surface-based convection diminishes. ..Gleason.. 01/16/2017 .PREV DISCUSSION... /ISSUED 1027 AM CST Mon Jan 16 2017/ ...East Texas/Arklatex/middle Mississippi Valley... A closed upper low over KS/northern OK at late morning will continue northeastward and reach the Lake Michigan vicinity by early Tuesday morning. Heights will rise across east TX coincident with a stalling front, while the cold front will remain more eastward progressive across the Ozarks/middle Mississippi River valley. Moderately strong south-southwesterly winds just above the surface will continue to transport a seasonally moist air mass northward, with near 60 F surface dewpoints reaching as far north as Memphis/northeast AR by early evening as air mass modification steadily occurs. Cloud cover may remain semi-prevalent across the warm sector today coincident with weak warm/moist advection amid a confluent pre-frontal regime. Even so, increasing moisture and cloud breaks/pockets of stronger heating could lead to MLCAPE around 500 J/kg this afternoon. As at least some afternoon intensification of updrafts occurs, 35-45 kt of effective shear would support semi-organized updrafts and line segments, potentially capable of marginally severe hail, damaging winds, and/or a brief tornado through the afternoon and evening. Aside from cloud cover, a sub-optimal phasing of large-scale ascent and more prevalent moisture/surface-based instability (to the south) should limit the overall severe risk today.Read more
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