Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1128 AM CST Mon Jan 16 2017 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE TX COASTAL PLAIN... ...SUMMARY... A marginal severe threat may develop Tuesday across parts of the Texas Coastal Plain. ...Synopsis... Positively tilted large-scale upper troughing will extend from the Upper Midwest to the Southwest Tuesday morning, and an embedded shortwave trough initially over the OH Valley and lower Great Lakes region will advance eastward to the Mid-Atlantic and New England. An upper trough/low will evolve northeastward from northwest Mexico to the southern and central High Plains through the period. A belt of enhanced (40-70+ kt) southwesterly/westerly mid-level flow will be present from TX to the OH Valley in association with both upper troughs. A surface low beneath the shortwave trough over the OH Valley/lower Great Lakes will also develop eastward to western NY by Tuesday evening, while a trailing cold front makes only slow southeastward progress across the OH/TN Valleys into the lower MS Valley and TX Coastal Plain. Forcing for ascent along the length of the cold front is forecast to remain weak through at least Tuesday afternoon, and better low-level moisture characterized by mid to upper 60s dewpoints will likely be confined to parts of coastal TX/LA. ...TX Coastal Plain to the Lower MS Valley... Isolated showers and thunderstorms may be ongoing at the start of the period across the OH Valley into the northern TN Valley. With modest diurnal heating occurring ahead of the front through Tuesday afternoon, isolated thunderstorms may develop along the length of the front from the eastern OH Valley southwestward into the lower MS Valley. Weak low-level convergence along the front, poor mid-level lapse rates limiting instability, and shortwave ridging over the TN Valley into the lower MS Valley suggest the severe risk should be minimal across these areas. Across the TX Coastal Plain, surface dewpoints generally in the mid to upper 60s may allow for surface-based convection to develop along/south of the front. This appears more probable Tuesday evening into Tuesday night as the glancing influence of ascent with an upper trough/low over the Southwest and southern High Plains begins to overspread the TX coast. There are some indications per NAM forecast soundings across this region that weak instability (around 500 J/kg MLCAPE) may be present through early Wednesday morning across the TX Coastal Plain. Although low-level winds are not forecast to be overly strong, sufficiently strong mid-level winds and some veering with height should support effective bulk shear values of 35-45 kt. Accordingly, any thunderstorms that occur along the TX Coastal Plain might pose some gusty wind risk if they can become surface-based, along with perhaps a brief tornado. ..Gleason.. 01/16/2017Read more
from SPC Forecast Products http://ift.tt/ws9HZn
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