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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.


Thursday, September 2, 2021

SPC Sep 2, 2021 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0248 PM CDT Thu Sep 02 2021 Valid 022000Z - 031200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL PLAINS... ...SUMMARY... A few severe thunderstorms will be possible across parts of Kansas and Nebraska with a couple tornadoes and damaging winds as the main threats. ...20Z Update... A small south-southeastward expansion has been made to the Slight Risk across parts of central into northeastern KS. A supercell recently developed across this area, and the environment downstream should be favorable for an isolated severe threat in the short term. See Mesoscale Discussion 1683 for more information. Otherwise, additional storms will probably increase in coverage and intensity across parts of central NE and western/central KS along and ahead of a surface trough, as destabilization in the wake of morning showers/storms is occurring across this region. Assuming surface-based storms develop, a threat for all severe hazards, including a couple of tornadoes, appears possible. Reference Mesoscale Discussion 1682 for additional details. ..Gleason.. 09/02/2021 .PREV DISCUSSION... /ISSUED 1130 AM CDT Thu Sep 02 2021/ ...Central Great Plains... A shortwave trough will decay as it tracks east from SD to the Upper MS Valley. A belt of strong low-level winds will shift east-northeast and subside somewhat with flow in excess of 30 kt at 850 mb generally becoming confined from eastern NE northward this afternoon. Ongoing convection and pervasive cloudiness within the warm conveyor region ahead of the surface cold front will limit boundary-layer heating beneath poor mid-level lapse rates. But pockets of clearing are underway just ahead of the cold front from northwest KS to western NE boosting destabilization into later afternoon. Thunderstorm development around this time frame appears most probable along the front from central NE to north-central KS, with activity spreading east-southeast into this evening. The setup should favor a mixed mode of a few clusters and embedded supercell structures, yielding primary threats of a couple tornadoes and damaging winds before waning after dusk. ...Eastern Great Basin to central Rockies... A positive-tilt mid-level trough will move slowly east over the northern Rockies through tonight, as an associated baroclinic zone sags slowly southeast across ID. Along and southeast of this baroclinic zone, the northwest edge of the monsoonal moisture plume (with upper 40s to low 50s dew points) persists from northern UT into central WY. Surface heating will result in weak buoyancy in the vicinity of the baroclinic zone, where isolated thunderstorm development is expected later this afternoon. This area will also lie along the southeast fringe of the stronger midlevel flow and effective bulk shear at or above 30 kt, such that a couple organized cells could produce outflow gusts near 60 mph within the well-mixed boundary layer. ...Southern LA... A diffuse front will drift south-southwestward into southern LA by late this afternoon, along the southwest fringe of a lingering midlevel trough over the Southeast. Moderate-strong buoyancy is expected along and south of the boundary, where at least widely scattered thunderstorms should form this afternoon. Though wind profiles will be rather weak, thermodynamic profiles will favor a few wet microbursts with the potential for localized wind damage. Read more LIVE:
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