SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1225 PM CDT Fri Oct 24 2025 Valid 251200Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF CENTRAL TEXAS INTO THE SABINE RIVER VALLEY... ...SUMMARY... Scattered severe thunderstorms are possible tomorrow (Saturday), across Texas into the Sabine River Valley. All severe hazards are possible. A couple of severe gusts or a brief tornado are also possible over parts of the Pacific Northwest. ...Synopsis... A mid-level trough will traverse the southern U.S., while an upper troughs ejects into the Atlantic and a more pronounced, larger scale upper trough impinges on the Interior West tomorrow (Saturday). Ahead of the southern U.S. upper trough, low-level troughing will encourage southerly return flow from the Gulf, resulting in airmass modification amid a warm-air/moisture advection regime. As upper support from the aforementioned trough encourages deep-layer ascent amid this moist airmass, thunderstorms will continue to develop and/or persist across Texas into the Sabine River Valley. Given adequate vertical wind shear accompanying this moist low-level airmass, multiple rounds of strong to potentially severe storms are likely. Strong flow aloft and associated vertical wind shear will overspread the Pacific Northwest, amid scant buoyancy, to support low-topped but potentially strong storms. ...Portions of Texas into the Sabine River Valley... Thunderstorms (perhaps in the form of an MCS), should be ongoing at the start of the period across TX, remnant from the Day 1 period. These storms will be preceded by a moist low-level airmass (i.e. at least mid to upper 60s F dewpoints), yielding 1000-2000 J/kg MLCAPE given modest mid-level lapse rates. A 35-45 kt southerly low-level jet will already be in place over eastern TX toward the Sabine River Valley, which will promote sizeable, curved low-level hodographs. As such, multicells and/or supercells embedded within this MCS will support all hazards during the morning hours, with the best chance for isolated tornadoes being with supercells that can remain discrete. These storms will approach the Gulf shoreline by around Noon, and are poised to weaken in the process. The progression of the earlier storms complicates severe potential for the central TX into the Sabine River Valley later Saturday into Saturday night. This is when the primary wave will overspread the region, coincident with strengthening and some eastward shift of the low-level jet. At least one additional, pronounced round of thunderstorms is expected to develop across central TX during the afternoon, and progress across LA during the evening/overnight hours. Should adequate airmass destabilization occur behind the preceding round of storms, deep-layer and low-level shear will be adequate to support supercell structures and subsequent upscale growth into a QLCS. In addition to large hail (especially over central TX), sizeable and curved low-level hodographs will support tornado potential. The best chance for tornadoes with the second round of storms will be over LA late Saturday, when the storms traverse the low-level jet axis. ...Portions of the Pacific Northwest... As broad and pronounced mid-level trough overspreads the Pacific Northwest through the morning to late afternoon hours tomorrow (Saturday), 80-100 kts of westerly mid-level flow will overspread the region. Some forecast soundings indicate 50 kt westerly flow extending as low as 700 mb in altitude, suggesting that little mechanical downward momentum transport is needed to support strong to potentially severe wind gusts. Strong deep-layer ascent, amid scant but possibly adequate buoyancy, will encourage the development of at least one (possibly multiple) low-topped convective bands. These bands (regardless of lightning potential) may produce a couple of severe gusts, especially over higher terrain, warranting the introduction of Category 1/Marginal risk probabilities. Low-end tornado probabilities have also been added to the OR coastline, where a few low-topped supercells may promote a landfalling brief tornado. ..Squitieri.. 10/24/2025
