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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.


Tuesday, September 19, 2023

SPC Sep 19, 2023 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1241 AM CDT Tue Sep 19 2023 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE SOUTHERN PLAINS... ...SUMMARY... Scattered severe thunderstorms are possible today and tonight across portions of the southern Great Plains. Large to very large hail and severe wind gusts are the primary hazards. ...Southern Plains... Low-amplitude short-wave trough is currently located over northeastern NM, shifting east-southeast as it tops the northern Mexico upper ridge. This feature will eject across the southern High Plains early in the period, shifting into central OK by 18z. Latest model guidance suggests a weak disturbance will quickly trail this feature which will dig southeast across northwest OK during the early-evening hours. Latest radar data supports water-vapor imagery with scattered convection now spreading across the western TX Panhandle, reflecting the leading edge of large-scale support. This activity should propagate across western OK early in the period as LLJ responds to the approaching short wave, focusing into central OK by 18z, then over northeast OK by 20/00z. With the dryline expected to hold near -100 longitude, timing of the short-wave trough will be too early for maximum daytime heating/destabilization. Early-day convection should limit heating across portions of northern/eastern OK such that a boundary will be reinforced across this part of the state. This early-day convection will likely be multi-cellular in nature, despite the increasing flow/strong deep-layer shear. Of more concern will be the potential for isolated supercells to develop in the wake of the lead short wave along the dryline by late afternoon. Strong surface heating is expected across western OK into west TX, and convective temperatures should easily be breached near this boundary by late afternoon. While large-scale forcing should prove negligible across the High Plains by peak heating, deep convection should develop within a strongly sheared environment. NAM forecast sounding at WWR at 23z exhibits MLCAPE in excess of 2000 J/kg, with steep lapse rates through 5 km. While low-level convergence will likely be weak, a few supercells are expected to evolve then propagate southeast. Forecast sounding for HBR is similarly buoyant and any storms that evolve in this environment should produce hail, some of it possibly exceeding 2" in diameter. Convection may be more isolated along the trailing dryline into northwest TX, but strong heating will lead to temperatures warming into the mid 90s over this region and CINH will prove minimal. Any storms that develop over northwest OK will track southeast, possibly along the aforementioned rain-reinforced boundary downstream. If so, some clustering could occur, especially during the latter half of the period. Confidence in storm coverage warrants a continuation of SLGT Risk at this time; however this will be assessed later this morning for possible changes if necessary. ..Darrow.. 09/19/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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