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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.


Wednesday, September 7, 2022

SPC Sep 7, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Wed Sep 07 2022 Valid 072000Z - 081200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE INTERIOR NORTHWEST AND NORTHERN ROCKIES/HIGH PLAINS... ...SUMMARY... Scattered thunderstorms may yield some severe wind gusts, a few of which could be significant, across parts of the interior Northwest and northern Rockies/High Plains this afternoon and early evening. ...20Z Update... No changes have been made to the Slight Risks across the interior Northwest and northern Rockies/High Plains. Latest surface observations show substantial warming/mixing of the boundary layer has occurred from eastern OR into ID and MT. Instability is expected to remain quite limited owing to the meager low-level moisture. Still, high-based thunderstorms spreading quickly east-northeastward across these areas should be capable of producing some severe downdraft winds given the deeply mixed boundary layer. The Marginal Risk across parts of south-central/southeast TX into southwest LA has been expanded to include more of central LA and far southwestern MS. See Mesoscale Discussion 1767 for more information on the near-term threat for isolated hail/wind with thunderstorms occurring across these areas. ..Gleason.. 09/07/2022 .PREV DISCUSSION... /ISSUED 1134 AM CDT Wed Sep 07 2022/ ...Interior Northwest/northern Rockies... A high-impact to extreme fire weather day is anticipated this afternoon into the evening. Please see the latest Day 1 Fire Weather Outlook for details on all hazards. Upper ridge will break down over the region as a vigorous shortwave trough over British Columbia amplifies and shifts east-southeastward toward the Canadian Rockies. Mid-level height falls accompanying this wave will overspread the interior Northwest as a belt of 50-kt 500-mb westerlies becomes centered from northeast Oregon/eastern Washington across northern Montana into southern Saskatchewan. Modest moisture along with record warmth will yield very deeply mixed boundary layers, especially east of the Rockies in Montana and across the Idaho Snake River Valley into southeast Oregon. Dry thunderstorms will increase in coverage this afternoon as both the boundary layer deepens and large-scale forcing for ascent strengthens. While buoyancy will be quite meager with MLCAPE of 300 J/kg or less, the extreme lapse rate profiles to 500 mb will support dry downbursts mixing to the surface from high-based/low-topped convection. Latest convection-allowing guidance are consistent in suggesting severe wind gusts will be prevalent within this fast-moving, skeletal activity. The eastern extent of this threat may include amalgamating convective outflows which could maintain severe gusts into eastern Montana despite diminishing lightning flashes this evening. ...Southeast/south-central Texas and southwest Louisiana... A minor mid-level impulse evident in water vapor imagery over the Ark-La-Tex will gradually move south-southwest into south Texas by this evening. A pocket of relatively cooler mid-level temperatures and steeper lapse rates attendant to this impulse should support a plume of moderate to large MLCAPE of 1500-3000 J/kg. While deep-layer shear will be modest and generally offset west of the greater instability/buoyancy, isolated marginally severe hail and strong to localized severe wind gusts will be possible as scattered thunderstorms develop this afternoon. Read more CHECK UPDATE ZOOM GRAPHIC
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