SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0643 AM CST Fri Jan 08 2021 Valid 081300Z - 091200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunder potential appears minimal over the U.S. mainland. ...Synopsis/Discussion... Low-level frontal passage -- associated with the cyclone analyzed at 11Z offshore Cape Fear -- will leave behind a boundary layer too dry and/or stable for overland thunderstorms east of the Rockies. However, brief thunder (below unconditional criteria) cannot be ruled out over or near the Outer Banks today, in association with a greater convective potential offshore near the northeastward- ejecting, occluding surface low. The associated mid/upper cyclone -- now covering most of KY/TN and portions of adjoining states -- will move offshore from NC around 06Z. In the Northwest, a negatively tilted trough was apparent in moisture-channel imagery from near Cape Mendocino northwestward across the Pacific, offshore from OR/WA. This perturbation should move quickly eastward/inland through the remainder of the morning. The most vorticity-laden southern portion of this feature should pivot southeastward across the northern Great Basin and intensify late in the period, becoming a strong shortwave trough and nearly a closed cyclone over southern UT by 12Z. Very isolated lightning cannot be ruled out over or west of the Cascades for another couple hours until the large-scale midlevel ascent and cooling aloft shift inland over unfavorably dry/cold air. However, the potential appears too isolated and brief for unconditional thunder probabilities at or above 10%. ..Edwards.. 01/08/2021
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