SPC May 19, 2017 1730 UTC Day 2 Convective Outlook

By Newsroom America Feeds at 19 May 13:33

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Fri May 19 2017 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE MISSISSIPPI AND OHIO VALLEYS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF CENTRAL/SOUTHERN TEXAS... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF TEXAS NORTHEASTWARD TO PENNSYLVANIA AND WEST VIRGINIA... ...SUMMARY... Strong to severe thunderstorms will be possible ahead of a cold front from southern/central Texas into the lower-to-middle Mississippi and Ohio Valleys Saturday and Saturday evening. Isolated strong/damaging wind gusts and hail will be the main concern. ...Synopsis... An expansive mid-level trough will gradually evolve eastward across the central U.S. Saturday, as multiple shortwave troughs rotate around its periphery from the southern Plains to the Great Lakes. The progression of the large-scale trough will be relatively slow, with ridging established to its east across the Appalachians and parts of the Atlantic Coast. Elsewhere, a shortwave trough will drop southeast across the Pacific Northwest. ...Portions of the Mississippi and Ohio Valley regions... A broad area of convection will likely be ongoing Saturday morning from the Ark-La-Tex northeastward to the lower Ohio Valley, with the middle Mississippi Valley convection likely aided by a south/southwesterly low-level jet. In turn, considerable uncertainty exists regarding the potential for early-day convective overturning/stabilization across parts of the Mississippi Valley. Nonetheless, from eastern portions of Arkansas to southern Illinois, any pockets of pristine air ahead of ongoing convection will feature moderate mixed-layer buoyancy amidst southwesterly mid-level flow around 40-50 kt. Therefore, a threat for a few damaging wind gusts and large hail reports would be present. Farther northeast, a warm front will be lifting north across Indiana and Ohio during the day. While forcing for ascent becomes considerably weaker across this region, upstream convection (as well as isolated storms organizing across the Ohio Valley) may grow upscale into a few downwind-propagating bowing segments. Aided by sufficient instability and westerly mid-level flow around 35-40kt, any such evolution would likely possess a threat for damaging wind gusts and perhaps a tornado or two, especially near the warm front where low-level shear will be maximized. Considering this potential, the Slight/Marginal Risks are expanded eastward. ...Portions of southern/central Texas... Augmented by overnight convection, a cold front will be progressing southward across Texas Saturday. Near/ahead of this boundary, despite a lack of strong heating, surface dew points in the upper 60s/lower 70s are expected to combine with modestly steep mid-level lapse rates to promote adequate buoyancy for the development of a few strong/severe storms during the day. Sufficient veering of winds with height and vigorous westerly upper-level flow will contribute a threat of large hail. Meanwhile, drier mid-level air atop rich boundary-layer moisture will enhance the damaging-wind threat some. As such, a Slight Risk is introduced across parts of the region. ..Picca.. 05/19/2017 Read more



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