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Archives for the SPC Convective Outlook are updated daily (approximately) with a live map at the beginning of each article. Follow the link at the end of the article to check for current updates on the NOAA/NWS Storm Prediction Center website. Also, see Archives for Chicago's hourly weather data on CARDINAL NEWS Magazine.


Tuesday, September 13, 2022

SPC Sep 13, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0244 PM CDT Tue Sep 13 2022 Valid 132000Z - 141200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS UPSTATE NEW YORK AND NEW ENGLAND... ...SUMMARY... Thunderstorms capable of damaging wind gusts, isolated hail and a brief tornado or two are possible today from eastern New York into parts of New England, mainly this afternoon into the early evening. ...20z update... A few severe storms will remain possible through this evening across upstate New York and southern New England ahead of a well-defined upper low. While cloud cover and early morning precipitation have limited severe potential thus far, some clearing has been noted across southern New England where upper 60s to low 70s F surface dewpoints are contributing to moderate destabilization. With effective shear values of 40 kt, a few organized line segments or supercell structures may evolve with a risk primarily for damaging wind gusts, hail, and perhaps a weak tornado. Minor adjustments to the western edge of the thunder area were made. Otherwise the marginal and Slight Risk areas remain unchanged, see the previous outlook for additional information. ..Lyons/Jewell.. 09/13/2022 .PREV DISCUSSION... /ISSUED 1109 AM CDT Tue Sep 13 2022/ ...Synopsis... An upper-level low over Lake Erie will gradually shift east/northeast through the day into the northeastern CONUS. As this occurs, a weak surface low will undergo some deepening as it moves northeast across the New England region. A trailing cold front, analyzed in latest surface observations from central NY southward along the East Coast, will focus thunderstorm development through the afternoon and evening hours. Across the western U.S., an upper-level trough over the Great Basin will phase with a shortwave disturbance moving into the Pacific Northwest. Ample moisture and lift ahead of these features will support scattered thunderstorm development across a broad swath of the inter-mountain West. A few strong wind gusts and marginally severe hail are possible with this activity, especially across portions of AZ/NM where deeper boundary-layer mixing is expected, but marginal wind profiles will limit the potential for widespread organized convection. ...New England... Thunderstorm development along the cold front is already underway at 16 UTC across parts of central NY. The 12 UTC ALB sounding sampled poor low and mid-level lapse rates, but ample moisture throughout the profile. Extensive cloud cover will likely limit the influence of daytime heating, but most model solutions suggest that only modest diurnal warming into the mid 70s is needed to support surface-based parcels with minimal inhibition and 500-1500 J/kg SBCAPE. Overall buoyancy magnitudes may be modulated by the poor mid-level lapse rates, and should generally decrease with northwestward extent away from the coast and the higher-quality moisture. The approach of the upper wave through the day will strengthen mid to upper-level winds and elongate hodographs. Nearly straight hodographs featuring effective bulk shear values near 35-45 knots will support storm organization, including the potential for supercell or two. Low-level flow is expected to remain fairly weak below 2-3 km, but may exhibit sufficient curvature to support low-level rotation and a brief/weak tornado threat. Read more CHECK UPDATE ZOOM GRAPHIC
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