SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0135 PM CST Mon Jan 04 2021 Valid 042000Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTHERN CALIFORNIA... ...SUMMARY... Isolated strong thunderstorms may produce gusty winds and/or a tornado this afternoon over a small part of northern California. ...DISCUSSION... No changes are made to the forecast for this issuance. ..Broyles.. 01/04/2021 .PREV DISCUSSION... /ISSUED 1024 AM CST Mon Jan 04 2021/ ...CA... No changes have been made to the ongoing forecast. Scattered lightning flashes are noted off the coast of northern CA in a post-frontal regime with cold temperatures aloft and steep lapse rates. This activity may move ashore this afternoon and evening, with a few thunderstorms affecting parts of western WA/OR and northern CA. Orographically backed low-level winds in the Sacramento Valley, coupled with strong southwesterly flow aloft and marginal CAPE values, will pose a risk of one or two low-topped supercells this afternoon. It is unclear if the storms would be sufficiently tall for charge separation. However, if activity can become sustained, there is the potential for gusty/damaging winds or a brief tornado or two. This threat should diminish around sunset.
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