SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1257 AM CDT Fri Jul 14 2023 Valid 141200Z - 151200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR MUCH OF THE CENTRAL PLAINS... ...SUMMARY... Thunderstorms producing damaging wind and sporadic hail are forecast over much of the central Plains on Friday. Isolated damaging gusts or marginal hail will also be possible over parts of the Mid Atlantic and southern New England, the Great Lakes, and the Mid-Mississippi Valley. ...Synopsis... A large upper low will remain over Canada, with an upper ridge over the Southwest. In between, moderate northwest flow aloft will persist over the Plains. To the east, various weaker embedded waves will affect parts of the OH Valley, Mid Atlantic, and Great Lakes. Moisture will remain plentiful east of the Rockies, with the only exception the northern Plains and upper MS Valley where drier air will spread in from the northwest. ...Central Plains... Ongoing and additional thunderstorm development this morning will have a significant impact on the severe weather threat across the Central Plains today. Convection across Oklahoma and the Texas Panhandle will likely maintain itself slowly southeastward this morning. Some 00Z CAM guidance showed this producing significant outflow and eroding the moisture reservoir across much of Oklahoma by 06-09Z. Current radar and observational trends suggest those CAM solutions are overdone with more localized impacts from ongoing convection. In addition, storms are starting to form across northeast Oklahoma in response to strengthening isentropic ascent amid a strengthening low-level jet. Some outflow/convective turnover is anticipated from these storms which could also impact the quality of the low-level moisture across Kansas this afternoon. Finally, there is uncertainty with regards to how robust elevated convection will be across southern Nebraska this morning. Some guidance shows upscale growth into a MCS into northern Kansas between 12 and 15Z while other guidance shows it either lingering in a more cellular storm mode or weakening during the morning before additional storms develop during the afternoon and grow upscale and move southeast. These factors complicate the forecast expectation for this afternoon. If a large reservoir of significant low-level moisture remains across Kansas today and upscale growth is sufficiently delayed for strong destabilization across Kansas, a threat for a more widespread, potentially significant wind event will persist. However, given the multitude of convective clusters ongoing which could impact this, confidence is low whether that solution will verify. More likely, some pockets of mid to upper 70s dewpoints will remain and have more localized regions with a greater severe wind threat within the slight risk area. If these corridors become more clear in later outlooks, an upgrade to enhanced could be justified. ...Great Lakes... A region of moderate to strong instability is expected to develop from eastern Iowa, across northern Illinois and southern Wisconsin and into southern/eastern Michigan this afternoon. A few weak shortwaves within the broader cyclonic mid-level flow across the Great Lakes may provide a focus for thunderstorms across eastern Michigan and northern Illinois during the afternoon/evening. An area of slightly higher severe weather threat may exist across northern Illinois this afternoon/evening where strong instability and sufficient shear to support supercells could overlap. However, ongoing thunderstorms across northern Iowa and western Wisconsin early this morning add some uncertainty to the degree of destabilization/recovery which may occur this afternoon. ...Mid-Atlantic into the Northeast... Numerous thunderstorms are expected along and east of the Appalachian crests today as convective inhibition should be mostly eroded by late morning given 70F dewpoints across most of the region. A broad region of moderate instability with effective shear around 30 to 35 knots should support multicell clusters with a primary threat for damaging wind gusts. Areas from eastern Pennsylvania into western Massachusetts and vicinity may have a slightly higher severe weather threat as more substantial heating and cooler temperatures aloft will foster greater destabilization and more robust updrafts. ...Mid-Mississippi Valley... A MCV is expected out of the Oklahoma thunderstorms which will move east across Arkansas during the day today. This will provide focus for thunderstorms this afternoon/evening from Arkansas to northern Alabama. Shear should remain weak with the better mid-level flow mostly north of this region, but at least some remnant EML and favorable lapse rates are expected across the region with very strong instability. Therefore, storms in this extreme instability could produce some damaging winds despite somewhat limited organization. ...Central High Plains... There is some CAM signal for supercell development within the moderate northwest flow across eastern Colorado both this afternoon (coming off the Mountains) and again overnight. Storm coverage may be isolated, but long hodographs should support supercells and the potential for large hail and severe wind gusts. ..Bentley/Wendt.. 07/14/2023
