Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 AM CDT Mon May 01 2017 Valid 031200Z - 041200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM CENTRAL/SOUTHERN TEXAS EASTWARD TO LOUISIANA... ...SUMMARY... A few severe storms will be possible from central/southern Texas eastward to Louisiana on Wednesday. ...Synopsis... With multiple shortwave impulses progressing east/southeast across the central US, a longer-wave trough will gradually amplify across the Plains states and Mississippi Valley through Wednesday night. Meanwhile, upstream ridging will overspread the Inter-Mountain West. ...Central/southern Texas eastward to parts of Louisiana... In response to a weak shortwave trough embedded in the southern stream, convection will likely be ongoing/expanding across parts of southeast Texas and potentially southwest Louisiana on Wednesday morning. With a plume of relatively steep mid-level lapse rates over much of the region and a veering wind profile with height, stronger cores may be capable of a few severe hail reports early in the day. Additionally, a tornado may be possible near a warm front close to the upper Texas Coast / Sabine Valley, where any surface-based updrafts would encounter enhanced storm-relative helicity. Of note, most guidance has trended westward and slightly narrower with the warm/moist sector supportive of such surface-based development. Considering ample subsidence/drying behind the current highly amplified central/eastern US system, this trend does not appear unreasonable. As such, confidence in anything more than marginal severe probabilities remains low for this early convection. Farther north, weak warm advection and/or convergence along a front pushing east/southeast will likely encourage convection across parts of north Texas eastward to the Ark-La-Tex through the morning and afternoon hours. Modest mid-level flow and weak/moderate buoyancy will likely yield a threat for a few instances of severe hail and perhaps strong wind gusts. More substantial buoyancy will likely materialize across portions of central/southern Texas during the afternoon hours, as surface dew points in the upper 60s/lower 70s combine with diurnal heating to yield upwards of 2000-3000 J/kg of MLCAPE. While some guidance suggests even greater buoyancy potential, the aforementioned early-day convection offers uncertainty regarding this upper-end scenario. Furthermore, weakened/veered 850-700mb flow in the wake of the initial impulse appears somewhat unfavorable for widespread organized updrafts. As such, thunderstorms are forecast to develop into clusters/segments along the cold front pushing southeast Wednesday afternoon/evening, with the potential for at least a few instances of large hail and strong winds. Considering the potential for moderate/strong buoyancy, some portions of the region could be upgraded to a Slight Risk in later outlooks as mesoscale details become clearer. ..Picca.. 05/01/2017Read more
from SPC Forecast Products http://ift.tt/GAMjPN
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