SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Wed Mar 26 2025 Valid 261630Z - 271200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS WESTERN PORTIONS OF WASHINGTON/OREGON... ...SUMMARY... Severe thunderstorms are expected across parts of the Pacific Northwest this afternoon and evening, with supercells possible west of the Cascades across Oregon into Washington. These storms may produce large hail, perhaps a tornado or two, and strong wind gusts. ...Pacific Northwest... Satellite imagery this morning shows an upper low approaching the coast with mostly sunny skies over much of the region. A 100 kt 500-mb speed max will rotate through the base of the trough and overspread coastal OR/WA by mid evening as the upper low shifts east. An associated cold front should arc from off the Washington Coast to southward along the Oregon Coast by evening. Cold-air advection in the mid levels and diurnal heating will contribute to steepening lapse rates, and the development of weak to locally moderate buoyancy (250-1500 J/kg SBCAPE) by mid-late afternoon. Strengthening large-scale forcing for ascent and negligible CINH will favor isolated thunderstorms developing by mid-late afternoon and increasing in coverage through the early evening. Forecast hodographs indicate supercells are likely with the stronger, more persistent updrafts. Large hail (1-2 inches in diameter) will be possible. The elongated and perhaps locally augmented hodograph in the vicinity of terrain favored areas (i.e., near the Columbia River with a modest easterly component) may enable a short-duration tornado risk. Severe gusts are also possible with the stronger cores and outflow surges as convection matures during the evening and gradually diminishing late. ...Texas Lower Rio Grande River Valley... A weak disturbance will approach the Rio Grande through mid afternoon with a cirrus shield expected to persist through peak heating. A moist boundary layer sampled by morning area raobs and some filtered heating will promote widely scattered to scattered storms developing this afternoon. Relatively weaker flow in the low to mid levels will limit overall storm organization, but transient supercell/multicells are possible. The stronger storms may be capable of a localized hail/wind threat. ...Southwest IA... A strengthening warm-air advection regime overnight from KS into MO/IA will likely lead to the development of widely scattered showers/thunderstorms in the vicinity of a warm front. Forecast soundings show elevated instability (1000 J/kg MUCAPE) developing as the profile moistens near 850 mb. A stronger storm capable of small to marginally severe hail cannot be ruled out, but the threat appears too limited to introduce low-severe probabilities. ..Smith/Mosier.. 03/26/2025