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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.


Sunday, July 4, 2021

SPC Jul 4, 2021 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Sun Jul 04 2021 Valid 042000Z - 051200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF THE CENTRAL AND SOUTHERN PLAINS AS WELL AS THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES REGION... ...SUMMARY... Scattered severe thunderstorms are expected over parts of the southern High Plains, and the western Lake Superior vicinity this afternoon and evening. A few intense storms may occur within the southern High Plains area where hail diameter could exceed two inches and wind gusts may reach in excess of 75 mph. ...Southern High Plains... Only minor adjustments have been made to previous forecast. See SWOMCD 1147 for more information. ...Upper Mississippi Valley and Great Lakes... No changes have been made to previous forecast. ..Dial.. 07/04/2021 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Jul 04 2021/ ...Southern High Plains... A belt of moderately enhanced/strengthening mid-level north-northwesterly winds are anticipated between the persistent anticyclone over the Four Corners area and a subtle MCV drifting south-southeastward across western Kansas. Robust heating of rich low-level moisture will contribute to a plume of moderate buoyancy with MLCAPE of 1500-2500 J/kg amid modest mid-level lapse rates. Initial thunderstorm development is expected over the Raton Mesa vicinity this afternoon and other parts of the Colorado Front Range, with a separate area of thunderstorms possibly developing in west/southwest Kansas near the MCV. Although southerly low-level flow should remain modest, pronounced veering of the wind profile with height will likely support a few supercells that may evolve into a southward-propagating cluster over the Panhandles. Scattered large hail and severe wind gusts, potentially along with a low-end tornado risk, will all be possible before the severe threat diminishes towards late evening. ...Upper Midwest... A low-amplitude shortwave trough over northwest Ontario will continue eastward through tonight. A surface wave over southeast Manitoba along a slowly eastward progressing cold front should move east along the international border today. Late afternoon convective development appears most probable near this surface wave from north-central to northeast Minnesota, with more isolated development possible farther southwest along the trailing front which should arc southwest towards the Middle Missouri Valley. The presence of low to mid 60s boundary-layer dew points coupled with very warm to hot temperatures should yield moderate buoyancy with MLCAPE of 1500-2500 J/kg. While deep-layer shear will be modest, a belt of 25-35 kt 700-mb westerlies to the south of the shortwave impulse will yield potential for loosely organized multicell clusters that might produce scattered damaging winds in the western Lake Superior vicinity through this evening. ...South-central/southeast Montana and northeast Wyoming... One or more low-amplitude mid-level impulses in conjunction with differential heating/weak upslope flow in vicinity of higher terrain/mountains should influence at least widely scattered thunderstorm development by mid/late afternoon. While vertical shear nor buoyancy will be overly robust, modest mid-level westerlies and a hot/well-mixed boundary layer could lead to some strong to locally severe storms capable of wind gusts and possibly some hail until around mid-evening. Read more LIVE:
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