{"id":439,"date":"2026-08-31T15:25:27","date_gmt":"2026-08-31T20:25:27","guid":{"rendered":"https:\/\/cimss.ssec.wisc.edu\/probsevere\/?p=439"},"modified":"2026-08-31T15:25:27","modified_gmt":"2026-08-31T20:25:27","slug":"northern-plains-shortwave","status":"publish","type":"post","link":"https:\/\/cimss.ssec.wisc.edu\/probsevere\/2026\/08\/31\/northern-plains-shortwave\/","title":{"rendered":"Northern Plains shortwave"},"content":{"rendered":"\n

A shortwave trough with moderate low-level flow spawned storms across the northern U.S. Below is the convective outlook discussion from the SPC at 16:30 UTC. <\/p>\n\n\n\n

...Northern High Plains into the northern Plains...\n   Recent satellite imagery shows a well-defined shortwave trough\n   moving eastward across southern Saskatchewan and western MT\/eastern\n   ID. A belt of stronger westerly flow aloft likely exists within the\n   base of this trough from eastern ID into western WY. Recent\n   mesoanalysis estimates 50 to 60 kt at 500 mb, but its actual\n   magnitude is uncertain. Showers and isolated thunderstorms are\n   already ongoing downstream of this wave, and the general expectation\n   is for these showers and thunderstorms to persist as the wave moves\n   eastward, eventually encountering a notably more unstable airmass\n   downstream.\n\n   Current surface observations show mid 60s dewpoints into the western\n   Dakotas, with upper 50s\/low 60s dewpoints farther west in eastern\n   MT. Afternoon high temperatures are expected range from the low to\n   mid 80s along the MT\/ND border into the low 90s farther south into\n   southwest SD. Despite relatively poor pre-frontal mid-level lapse\n   rates, the resulting temperature\/dewpoint combination will support\n   MLCAPE ranging from around 500-1000 J\/kg across eastern MT and the\n   western Dakotas to closer to 2000 J\/kg across the central Dakotas.\n   Some low-level stability may linger, but should be overcome by the\n   strong forcing, and the development of a line of strong to severe\n   storms is anticipated. Strong to severe gusts will be the primary\n   risk, with some instance of gusts from 65 to 80 mph possible.\n   Maximum storm intensity and highest severe coverage is currently\n   forecast to occur from the ND\/SD\/MT border intersection vicinity\n   eastward into south-central ND and north-central SD. Decreasing\n   buoyancy is expected from the central Dakotas eastward, with\n   gradually decreasing storm intensity expected as the line of storms\n   moves into this region this evening.\n\n   ...Central High Plains...\n   Increased coverage and depth of the thunderstorms across UT indicate\n   the presence of secondary area of ascent south of the primary\n   shortwave trough, perhaps tied to a convectively augmented vorticity\n   maximum. Expectation is for this vorticity maximum to progress\n   eastward, persisting across the central Rockies before entering\n   deeply mixed boundary-layer in place over the central High Plains.\n   High-based storm character coupled with steep low-level lapse rates\n   will support the development of strong outflow, and gusts from 60 to\n   75 mph are possible.<\/pre>\n\n\n\n
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ProbSevere v4 probabilities of any severe hazard in the next 45 minutes (contours), NWS severe thunderstorm warnings (orange polygons), and local severe wind reports (blue circles) in the next 45 minutes.<\/figcaption><\/figure>\n\n\n\n
The spatially based ProbSevere v4 had moderate probabilities ahead of the supercell in far northwest South Dakota. However, smaller, short-lived cells in the county to its south had < 10% probabilities, yet produced numerous wind reports. The NWS severe thunderstorm warning also was a bit late, indicating the first reports spurred the warning. <\/p>\n\n\n\n
Further south, towards Rapid City, SD, a congealed outflow boundary also produced many damaging or measured wind gusts. While the NEXRAD level-II reflectivity looked fairly benign, the doppler velocity showed the strength of the winds. Surprisingly, a warning was not issued this far south. <\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
We can easily see that a situation like this is difficult for PSv4. The MRMS quality-controlled out the gust front in reflectivity, though the low-level MRMS azimuthal shear should have been able to help a bit. This is an example where the level-II data may have helped produce more reasonable probabilities of severe wind. <\/p>\n\n\n\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
A shortwave trough with moderate low-level flow spawned storms across the northern U.S. Below is the convective outlook discussion from the SPC at 16:30 UTC. …Northern High Plains into the northern Plains… Recent satellite imagery shows a well-defined shortwave trough moving eastward across southern Saskatchewan and western MT\/eastern ID. A belt of stronger westerly flow […]<\/p>\n","protected":false},"author":14,"featured_media":443,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[5],"tags":[6],"class_list":["post-439","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-psv4","tag-psv4"],"acf":[],"_links":{"self":[{"href":"https:\/\/cimss.ssec.wisc.edu\/probsevere\/wp-json\/wp\/v2\/posts\/439","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cimss.ssec.wisc.edu\/probsevere\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cimss.ssec.wisc.edu\/probsevere\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/probsevere\/wp-json\/wp\/v2\/users\/14"}],"replies":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/probsevere\/wp-json\/wp\/v2\/comments?post=439"}],"version-history":[{"count":4,"href":"https:\/\/cimss.ssec.wisc.edu\/probsevere\/wp-json\/wp\/v2\/posts\/439\/revisions"}],"predecessor-version":[{"id":445,"href":"https:\/\/cimss.ssec.wisc.edu\/probsevere\/wp-json\/wp\/v2\/posts\/439\/revisions\/445"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/probsevere\/wp-json\/wp\/v2\/media\/443"}],"wp:attachment":[{"href":"https:\/\/cimss.ssec.wisc.edu\/probsevere\/wp-json\/wp\/v2\/media?parent=439"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/probsevere\/wp-json\/wp\/v2\/categories?post=439"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/probsevere\/wp-json\/wp\/v2\/tags?post=439"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}