Widespread smoke and haze will continue to result in poor air quality over much of the San Francisco Bay Area through the weekend. Otherwise, dry weather with mild temperatures are forecast to persist through early next week. A significant pattern change appears likely starting around the middle of next week, with the potential for widespread periodic rainfall during the second half of the week.
As of 09:17 AM PST Friday, Smoke and poor air quality will continue to impact the region today, with the Bay Area seeing the worst of the impacts. Visibilities are reduced regionwide with visibilities as low as 1 mile in Oakland and 1 to 2 miles at other reporting locations around the Bay. Not expecting much change in smoke coverage across the Bay Area as offshore flow continues to drain smoke down the Central Valley through the Golden Gate gap and out over the coastal waters. Coastal areas may see some minor improvements in air quality with the possibility for some weak onshore flow this afternoon. However, there is abundant smoke over the coastal waters so not expecting onshore flow to improve conditions meaningfully. Smoke and poor air quality will continue to be an issue through early next week until a pattern change occurs.
Overnight lows remained cool in valleys last night, especially across the north bay where low to mid 30s were common. Smoke will continue to keep high temperatures several degrees cooler across the Bay Area than surrounding areas with highs in the mid 60s. Other areas will see highs in the low-mid 70s. May see an increase in smoke in our southern regions this afternoon as onshore flow advects smoky air inland. Dry conditions are expected through Tuesday. A major pattern change is still on track for the middle of next week and into the holiday weekend. This will help to remove smoke and bring rainfall to the area.
As of 02:52 AM PST Friday, The main impacts across the region in the short-term will continue to be smoke, haze and associated poor air quality as a result of the Camp Fire inland to our north. Poor visibility, below 1 1/2 SM at times, is being reported across the greater San Francisco Bay Area with temperatures ranging from the middle 30s in our colder inland valleys to upper 40s near the coast. Given the weak offshore flow aloft, air quality is not forecast to improve much through the day with unhealthy to very unhealthy conditions forecast (by the Bay Area Quality Management District) across the Bay Area while slightly better conditions are expected over the Monterey Bay region.
The forecast models do indicate a slight increase in onshore flow near the coast this weekend which may help to improve conditions. May even see areas of low clouds develop over the Pacific late tonight with the potential for coastal intrusion by Saturday morning. Something that will need to be closely monitored as smoke may actually get trapped beneath the low level inversion. Regardless, dry weather conditions will persist along with temperatures above seasonal averages each afternoon through the weekend and into early next week. Overnight conditions will be seasonably cool, especially inland away from the coast.
Forecast confidence continues to increase regarding a major pattern shift late next week that would bring unsettled weather conditions to the region. An initial upper level system is forecast to develop over the eastern Pacific and approach the southern California coast early next week, missing our region. However, the medium range models are in better agreement with subsequent systems approaching the region during the second half of the week. The GFS, ECMWF and Canadian are in decent agreement with the potential for widespread rainfall developing over the region as early as Wednesday. Additional systems appear likely to impact the region around Thanksgiving and potentially into the following holiday weekend as well. With this said, timing and strength of each system remains difficult to pin-point at this time given model-to-model and run-to- run differences. Regardless, a more active pattern is appearing more likely late in month which would also help to improve air quality region-wide.
As of 4:08 AM PST Friday, MVFR-IFR in smoke. Mainly light winds. Poor to very poor slant range visibilities.
Vicinity of KSFO, MVFR-IFR visibility in smoke, light wind. Poor to very poor slant range visibility.
SFO Bridge Approach, Similar to KSFO.
Monterey Bay Terminals, MVFR visibilities in smoke, light winds except SE 5 to 10 knots in the Salinas Valley this morning.
As of 2:52 AM PST Friday, Generally light winds will continue through the weekend and early next week. A mixed moderate northwest swell and light southerly swell will also persist. Wet weather develops by the middle of next week.