SPC Convective Outlooks

SPC Aug 4, 2020 1300 UTC Day 1 Convective Outlook (Di, 04 Aug 2020)
SPC 1300Z Day 1 Outlook Day 1 Outlook Image Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0704 AM CDT Tue Aug 04 2020 Valid 041300Z - 051200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS PORTIONS OF THE NORTHEAST... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS CENTRAL HIGH PLAINS... ...SUMMARY... Tornadoes will be most likely through this afternoon from Delaware into southern New England, with a lingering threat for a couple tornadoes across northern New England this evening. Scattered large hail and severe wind gusts will be possible across the central High Plains from mid-afternoon to mid-evening. ...DE to New England... As T.C. Isaias rapidly shifts northeastward today, an accompanying very moist low-level environment will permit maintenance of weak buoyancy across the coastal plain of the Northeast into southern New England. Clusters and cells of shallow convection to the north and east of the circulation center will continue to pose a risk for tornadoes. The greatest risk will be where mid 70s surface dew points can become coincident with immense low-level hodograph curvature from DE to the NYC tri-state area. Most guidance is consistent in suggesting the very rich surface moisture will become pinched off across parts of southern New England later today. This suggests the overall tornado risk should decrease this evening as it spreads into northern New England. ...Central High to Northern Great Plains... A broad plume of 50s surface dew points is prevalent ahead of a lee surface trough, a low-amplitude shortwave impulse near the MT/SK border, and an MCV near the SD/MT border. The greatest buoyancy this afternoon should develop along the central High Plains portion of the lee trough amid very steep low to mid-level lapse rates, with relatively weaker mid-level lapse rates in the Dakotas. Scattered thunderstorms should initiate near the Front Range during the mid-afternoon and spread east within moderate mid-level west-northwesterlies. The setup should yield supercells initially producing large hail, some of which may be significant, from eastern CO into the NE Panhandle. Conglomerating cold pools should tend to foster multiple clusters as activity spreads towards the KS/CO border longitude. A dearth of surface-based instability with eastern extent in KS/OK suggests waning severe potential during the evening even though an elevated MCS should persist to the southeast. Farther north, scattered thunderstorms are expected as well, mainly across western to central ND in closer proximity to ascent tied to the approaching shortwave trough. Weak mid-level lapse rates should be a limiting factor and may result in only isolated coverage of severe hail and wind. Have expanded Marginal Risk northward for this threat. ..Grams/Jewell.. 08/04/2020 Read more
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