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Thursday, July 8, 2021

SPC Jul 8, 2021 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0244 PM CDT Thu Jul 08 2021 Valid 082000Z - 091200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF THE NORTHERN HIGH PLAINS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM A PORTION OF THE MIDDLE ATLANTIC AND NORTHEAST STATES AS WELL AS THE OHIO VALLEY... ...SUMMARY... Scattered severe thunderstorms capable of very large hail and damaging winds are expected across parts of the northern Great Plains late this afternoon and evening. A few brief tornadoes are possible across eastern North Carolina to southeast Virginia through afternoon/early evening. Other severe storms are possible across the Ohio Valley to Northeast States. ...Discussion... Only minor adjustments have been made to previous forecast for this update. ..Dial.. 07/08/2021 .PREV DISCUSSION... /ISSUED 0119 PM CDT Thu Jul 08 2021/ ...Eastern Montana/Dakotas... A shortwave trough near the MT/Alberta border will progress east then southeast into the Dakotas through tonight. Attendant surface cyclone should gradually track east-southeast across northeast MT through this afternoon. A lee trough will become established to the south of this low near the MT/WY/Dakotas border longitude, while a slow-moving warm front arcs from western ND to a secondary front/trough intersection near the south-central SD/north-central NE border. Scattered thunderstorms are expected to develop near the surface cyclone/trough/front intersection across far eastern MT and western ND/northwest SD amid strong boundary-layer heating west of the trough. A plume of moderate buoyancy given rather steep mid-level lapse rates amid a rather elongated hodograph will foster discrete splitting supercells. This setup appears favorable for very large hail in the first few hours of convective evolution. Uncertainty becomes greater with time and southern extent owing to widespread pronounced MLCIN across much of SD into NE. A separate corridor of more probable elevated thunderstorm development is anticipated over the Mid-MO Valley near the nose of the low-level jet where parcels can become saturated atop the low-level inversion. This corridor should have a threat for isolated severe hail overnight. ...Eastern NC/southeast VA to the Mid-Atlantic Coast... As TC Elsa continues northeastward, a moist environment and strong low-level winds on the periphery of Elsa will remain favorable for tornadoes across eastern NC into southeast VA. The tornado threat will likely remain marginal/conditional this evening into tonight as Elsa tracks along the Mid-Atlantic Coast. ...Northeast States... Clusters of showers/thunderstorms are ongoing at midday across the region, particularly across far southeast New York into western New England. More considerable cloud cover is also generally prevalent across the region as compared to prior days. More appreciable destabilization will tend to remain confined to the Chesapeake/DE Bays towards the New York City tri-state area, where some cloud breaks are noted within morning visible satellite imagery. Although the degree of destabilization is a bit uncertain, isolated severe thunderstorms will be possible across the region with thunderstorm wind damage as the primary severe risk. Areas such as northeast PA/northern NJ into southern NY/NYC Metro and southern New England will continue to be reevaluated and monitored for a somewhat greater severe risk later today, which could include potential for some transient supercells. ...Lower Great Lakes/Ohio Valley... Scattered thunderstorms are expected to increase this afternoon along/ahead of a southeastward-advancing cold front. Mid-level lapse rates are not overly steep, but ample moisture and steepening low-level lapse rates coincident with 25-30 kt effective shear will support some semi-organized/sustained storms this afternoon through early/mid-evening. Isolated damaging winds are the primary concern. Portions of southern Indiana/northern Kentucky into southwest Ohio have been upgraded for a what appears to be a more probable corridor of storms capable of wind damage. ...Middle Texas Gulf Coast... A belt of enhanced low-level southeasterly winds near a weak mid-level low may prove adequate for a brief tornado or two today and tonight. This risk should remain confined to immediate coastal areas. Read more LIVE: spc.noaa.gov