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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, August 8, 2023

SPC Aug 8, 2023 1300 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0751 AM CDT Tue Aug 08 2023 Valid 081300Z - 091200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS NORTHEAST CO...SOUTHWEST NE...FAR NORTHWEST KS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SEPARATELY ACROSS PARTS OF THE SOUTHEAST... ...SUMMARY... Scattered severe thunderstorms are expected across parts of the central High Plains during the late afternoon into tonight. Large to very large hail, severe gusts, and a tornado or two will be the potential hazards. Scattered damaging winds and isolated severe hail will also be possible through around sunset across parts of the Southeast. ...Central High/Great Plains... A shortwave trough over southeast ID will progress into the central High Plains by tonight. As this occurs, modest lee troughing will support south-southeasterly low-level winds, which should allow for air mass recovery in the wake of yesterday's MCS amid a stout elevated mixed layer. This low-level flow regime beneath 35-45 kt mid-level zonal flow will yield an elongated, nearly-straight hodograph. This will overlap a confined corridor of MLCAPE from 2500-3000 J/kg centered on the northeast CO/southwest NE border. Initial high-based thunderstorm development will occur off the higher terrain of southeast WY and north-central CO by mid-afternoon and spread east, impinging on the larger buoyancy environment. A few splitting supercells are expected with a north/south-oriented cluster likely evolving relatively quickly as outflows consolidate towards the CO/NE/KS border area. The potential for a longer-track discrete supercell appears greatest along the southern periphery of convective development owing to lack of interference from other supercells and closer proximity to the upper jet centered on southern CO/KS. Very large hail, significant severe wind gusts, and a tornado or two are all possible. Uncertainty is greater with the overall degree of severe threat tonight. Convective coverage will indubitably increase as a nocturnal low-level jet strengthens northward from the southern High Plains and large-scale ascent waxes ahead of the aforementioned shortwave trough. Given pronounced MLCIN expected across much of western KS at peak heating, prospects for a severe-producing MCS initially appear questionable. It seems plausible that convection may tend to regenerate across northeast CO to the NE/KS border area during the evening before finally growing upscale overnight as additional elevated convection develops east-southeast. As such, a long-duration threat for sporadic large hail and isolated severe wind gusts may be sustained in/near the cat 3/ENH risk area, with lower confidence in the spatial extent of these threats towards central parts of NE/KS. ...Southeast... An MCS is ongoing from the Ark-La-Miss back into far eastern OK and generally appears to have remained sub-severe over the past few hours. The primary short-term uncertainty is exactly when this MCS will turn the corner today and begin to accelerate east-southeast with a damaging wind threat. See MCD 1905 for further discussion regarding the threat this morning. In the wake of yesterday's severe MCS, a pronounced buoyancy gradient is roughly oriented from west to east across central portions of MS/AL/GA. Amid modest west-southwesterly low-level flow this gradient will move slowly through the day but intensify as buoyancy becomes large across south AL/GA and north FL. The current MCS or remnants of it will likely progress along this buoyancy gradient while attempting to develop southward into it from midday through the afternoon. While the large-scale outflow from this activity will likely outpace the stronger mid-level flow to its northwest, there will remain adequate deep-layer shear for organized multicell clustering with scattered damaging winds as the primary hazard. ...New England... A shortwave trough from southern QC to the Lower Great Lakes will slowly move east across the St. Lawrence Valley and New England through tonight. The low-level warm conveyor region ahead of this trough will largely become divorced from surface-based buoyancy by midday. Until that occurs, a low probability/brief tornado threat remains possible where low 70s surface dew points are present across southern New England. More probable convective development this afternoon is anticipated over western New England where deep-layer shear will be weak in closer proximity to the trough axis and potential for organized severe thunderstorm development is low. ...Northern MN and eastern ND... A shortwave trough digging across MB and northwest ON will aid in a cold front pushing south-southeast across northern MN and trailing into ND. An adequate combination of deep-layer shear and instability should support a marginal and isolated severe wind/hail threat during the late afternoon to early evening. ..Grams/Dean.. 08/08/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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CHICAGO UTC-6 during CST (Central Standard Time, e.g., winter)
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