Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0402 AM CDT Sat Apr 01 2023 Valid 041200Z - 091200Z ...DISCUSSION... Medium-range models continue to indicate that the westerlies will become rather amplified across the mid-latitude Pacific into western North America by late next week into next weekend. It appears that this will include building mid-level ridging centered near the Pacific coast, with downstream developments a bit more unclear. However, beneath at least a broadly confluent mid/upper flow, cold surface ridging may tend to prevail east of the Rockies, with generally low severe weather potential. Prior to these developments, strong surface cyclogenesis is forecast to proceed across the central Great Plains into the Upper Midwest Tuesday through Tuesday night, in response to a significant short trough emerging from the Intermountain West. It still appears that, as the center of the deepening cyclone migrates from the north central Kansas vicinity through eastern Nebraska and western Iowa during the late afternoon and early evening, a trailing dryline advancing across the Missouri/Kansas border vicinity might provide one focus for intense thunderstorm initiation. There remains at least some signal within the various model output that convection may initiate earlier within the open warm sector to the east, and it remains unclear what influence this might have on subsequent thunderstorm development. Barring this complication, a period of sustained, long track discrete supercell development may be possible, as strong southwesterly deep-layer mean flow advects cells away from the dryline through the moist warm sector. This probably would be accompanied by potential for strong tornadoes and large hail. Thereafter, as a trailing cold front overtakes the dryline and surges eastward across the lower Missouri/middle Mississippi Valleys, an organizing squall line may be accompanied by strong, damaging wind gusts and a few tornadoes. As the occluding surface cyclone continues across and northeast of the Upper Midwest/Great Lakes region on Wednesday, there may be at least some continuing risk for severe thunderstorm development across parts of the lower Great Lakes/upper Ohio Valley and perhaps parts of the northern Mid Atlantic. However, due to a number of lingering uncertainties, this remains much more unclear at the present time.
