October 11, 2020 – The PG&E Emergency Operations Center will be activating this evening to begin preparations for a potential Diablo wind event lasting from Wednesday through Thursday or potentially Friday morning. The forecast now shows Elevated PSPS potential in Zones 2, 3, 4, 5 and 8 for the upcoming event.
Please note that PSPS is not executed across entire Zones and much more detailed maps where PSPS is being considered will be provided as the event gets closer. This is only intended to provide a high level overview. PSPS decisions are made at more granular levels based on high resolution data; thus, only a portion of a zone may experience a PSPS event.
At this time, the highest probability areas for observing a PSPS are the Northern Sierra Nevada foothills, the mid and higher elevations in the Sierra generally north of Yosemite (northern portion of Zone 8), the North Bay mountains and potentially pockets of the Santa Cruz mountains.
At this time, the weather event is expected to begin Wednesday afternoon/evening and continue through Thursday morning.
A second period of winds may develop Thursday evening through Friday morning in the Northern Sierra and North Bay mountains and Zones 2 and 5 are in elevated on Friday to highlight that potential. The start of the event is more than 3 days away so event details will likely change as forecast models evolve. We will have more clarity on potential cities and counties impacted in the next 48 hours. Please stay tuned to future updates.
Details: Onshore flow will continue today and dry northerly winds up to 30 mph are expected across the Sacramento Valley through the day. A warming and drying trend will then take place this week as high pressure builds in across the state. Wednesday, northerly winds will develop through the Sacramento Valley through the day and will shift to the north/northeast Wednesday night and continue into Thursday or Friday. The strength of these winds is somewhat uncertain, but gusts at or above 50 mph are looking possible in elevated terrain in the North Bay and Northern Sierra. While onshore flow, cooler weather and higher RH this weekend has allowed fuels to recover some moisture, fuels are expected to quickly dry out once warmer conditions return next week and dry offshore winds develop. Fire danger will rapidly increase mid to late this week as dead fuels quickly dry out under warmer and drier conditions and offshore winds. The latest National Interagency Fire Center wildland fire potential outlook continues to favor above normal large wildland fire potential for most of Northern CA for October followed by normal large fire potential for November and December.