SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1200 AM CDT Tue May 04 2021 Valid 051200Z - 061200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS WEDNESDAY ACROSS NORTHEASTERN GULF COASTAL AREAS INTO THE SOUTHERN MID ATLANTIC COAST REGION... ...SUMMARY... Strong thunderstorms may impact northeastern Gulf coastal areas early Wednesday, with additional strong storms possible across parts of the southern Mid Atlantic coast region during the day. A few of these storms may pose at least some risk for severe hail and potentially damaging wind gusts. ...Synopsis... Models indicate that the leading edge of an amplified belt of westerlies emanating from the northern mid-latitude Pacific will gradually continue to develop inland across the Pacific Northwest/British Columbia coast, Wednesday through Wednesday night. This likely will include a mid-level ridging, which probably will begin to sharpen as it shifts into the northern U.S. intermountain region and Canadian Rockies vicinity. It appears that blocking may become at least a bit more prominent in the downstream flow, centered near the Labrador Sea, and a broadening mid-level low centered near James Bay may move little through this period. South of this feature, models indicate that a more prominent cyclonic mid-level flow will continue to evolve across the Mississippi Valley through the Atlantic Seaboard. This is forecast to occur as at least a couple of short wave perturbations dig to the lee of the upstream ridging, and remnant perturbations, emerging in prior days from the Southwest, progress across the Atlantic Seaboard. There now appears greater consensus among the various models that one of these short waves may provide support for cyclogenesis within pre-cold frontal surface troughing near the northern Mid Atlantic coast by the beginning of the period. It appears that this will proceed across the southern New England coast vicinity into the Atlantic Wednesday through Wednesday night, with the trailing cold front advancing across the middle through southern Atlantic Coast region, and into the northern Gulf of Mexico. ...Mid Atlantic through parts of the Southeast... A large, composite pre-frontal convective outflow boundary may still be a focus for vigorous thunderstorm activity at 12Z Wednesday, across southern Louisiana/Mississippi and Alabama coastal areas into parts of the Florida Panhandle and southern Georgia. Although deep-layer mean wind fields and shear may be in the process of weakening, and becoming more marginal for organized thunderstorm development, continuing inflow of seasonably moist air (supportive of CAPE in excess of 1000 J/kg) may be sufficient to maintain at least some risk for damaging wind gusts and perhaps some hail, before activity advances offshore. Stabilization of upstream lapse rates, associated with widespread convective overturning Tuesday through Tuesday night, will be a factor mitigating convective potential across the northeastern Gulf coast vicinity, as well as across much of the southern into mid Atlantic Seaboard. Additionally, it now appears more probable that early veering of flow to an increasingly westerly component, coupled with mid-level subsidence and drying, will suppress convective potential to the east of the southern Appalachians. However, at least some model output suggests that another short wave impulse approaching the Appalachians during the day could provide support thunderstorm development by late afternoon, particularly across the North Carolina Piedmont. A corridor of stronger pre-frontal heating and residual low-level moisture may contribute to thermodynamic profiles supportive of at least some risk for hail and damaging wind gusts. This will tend to spread eastward toward the southeast Virginia/North Carolina coastal plain, beneath 40-50+ kt west-southwesterly 500 mb flow. ..Kerr.. 05/04/2021
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