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Sunday, May 30, 2021

SPC May 30, 2021 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1255 AM CDT Sun May 30 2021 Valid 301200Z - 311200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON AND EVENING ACROSS EASTERN NEW MEXICO INTO PARTS OF WESTERN TEXAS AND ADJACENT PORTIONS OF THE OKLAHOMA PANHANDLE... ...SUMMARY... Severe thunderstorms are possible east of the southern Rockies into adjacent portions of the southern Great Plains, mainly late this afternoon into tonight. This may include a few supercells, and perhaps the evolution of an organized cluster of storms across parts of northeastern New Mexico into the Texas South Plains. ...Synopsis... Models indicate that most areas east of the Rockies will remain seasonably cool and stable, while relatively warm, dry conditions prevail across much of the West. This is in association with a generally weak, but amplified, split mid/upper flow prevailing across much of North America. Initially, in southern mid-/subtropical latitudes, this includes mid-level ridging across the southern Rockies/Great Plains, flanked by troughing across the California coast/Baja into the southern Great Basin/Colorado Plateau and across the Appalachians into Atlantic Seaboard. In northern mid-latitudes, this includes mid-level troughing across the central Canadian Provinces into northern Great Plains, flanked by ridging across British Columbia and the Pacific Northwest and across the eastern Canadian provinces. Today through tonight, a significant perturbation within the eastern U.S. troughing is forecast to accelerate across the Appalachians into the northern Atlantic Seaboard, as the northern branch troughing migrates toward the Great Lakes, but weak mid-level troughing likely will linger near the south Atlantic Seaboard into the southeastern Gulf of Mexico/Caribbean. Upstream, a broad cyclonic mid-level circulation emerging from the subtropical eastern Pacific may accelerate across and northeast of northern Baja, with large-scale ridging being maintained across the southern Rockies/Great Plains. However, it appears that another perturbation emerging from the Southwestern troughing will migrate into and through the larger-scale ridging across and east of the southern Rockies later today through tonight. ...Parts southern Rockies/Great Plains... One perturbation is already crossing the Front Range/Sangre de Cristo Mountains vicinity, contributing to ongoing, increasingly widespread thunderstorm development across the adjacent higher plains. Embedded within weak (10-20 kt), deep-layer westerly ambient mean flow, this activity will only slowly spread eastward through daybreak, with associated precipitation and outflow reinforcing a frontal zone near the Raton Mesa vicinity into the Texas/Oklahoma Panhandles. South of this baroclinic zone, southeasterly near-surface flow will maintain a relatively moist boundary layer across southern and western Texas into the Sacramento and Sangre de Cristo Mountains (and southern slopes of the Raton Mesa), where models suggest that lapse rates may remain steep enough to support mixed-layer CAPE on the order of 1000-2000 J/kg by midday. In response to this destabilization, and orographic forcing, storms may initiate off the higher terrain by early afternoon. It appears that stronger difluent/divergent upper flow may focus the most widespread storm development across the Sangre de Cristo Mountains/Raton Mesa vicinity. In the presence of at least modest deep-layer shear, largely due to veering of profiles in lower/mid-levels, but probably aided by a belt of 50+ kt southwesterly flow in the 300-250 mb layer, this may initially include the evolution of a few supercells posing a risk for severe hail and wind, while slowly propagating off the higher terrain. There has been a signal in various model output that storms may gradually consolidate into a fairly extensive upscale growing cluster, including a possible evolving MCV, across northeastern New Mexico into the Texas Panhandle vicinity. Given the modest nature of the ambient wind fields, and the lack of more robust CAPE, it remains unclear how strong this will be. However, before instability wanes by late tonight, there appears at least some potential for the evolution of an organizing cluster capable of producing one or two swaths of strong wind gusts. It is possible that severe weather probabilities could still be increased in later outlooks across this region. ...Florida Peninsula... In the presence of generally weak low-level flow, Atlantic and Gulf Coast sea-breezes appear likely to advance inland with strong heating over the interior peninsula. As they do, aided by large-scale forcing for ascent associated with the approaching weak mid/upper troughing, storms are expected to initiate in the presence of weak to moderate CAPE. As the boundaries gradually converge over the interior peninsula by late afternoon, storms may become increasingly widespread and consolidate, accompanied by potential for some of this activity to produce damaging downbursts. ..Kerr/Squitieri.. 05/30/2021 Read more LIVE: spc.noaa.gov