Red Flag Warning extended through Tuesday

October 26, 2020 – Extreme fire weather conditions will continue early this week due to gusty winds, low humidity values, and dry fuels. Winds will decrease this afternoon, but locally strong winds will occur again tonight across the higher elevation ridges. Lighter winds are expected by mid-week, but very dry conditions will persist.

Discussion

Strong northeast wind event continues across the region early this morning. Widespread wind gusts in the 30s to mid 40s mph continue along the western edge of the Sacramento Valley and southward into the Delta while local gusts of 40 to 75 mph have been occurring over the foothills and higher elevations of the northern Sierra. The surface pressure gradient is holding around 10-11 mbs both MFR-SAC and RNO-SAC. KDAX VWP currently indicating winds of 45-55 kts from 1-3k ft above the surface, which is around 10 kts lower compared to late Sunday evening. Current RH’s are mostly in the teens to mid 20s percent.

Critical fire weather conditions continue across the area due to the gusty winds, very low RH, and record dry fuels. Despite these conditions, fortunately IR difference imagery is not indicating any new significant fire starts across interior NorCal overnight.

The surface pressure gradient is forecast to slacken by late morning. However, gusty winds will continue across the region, particularly across the southern half of the Sacramento Valley and across the higher elevations of the northern Sierra. Extension of the wind advisory may need to be considered for those areas.

Breezy northerly winds will continue Tuesday across the Sacramento Valley and surrounding terrain including the northern Sierra. Winds won’t be as strong as today, but fire weather conditions will remain elevated to critical.

Eastern Pacific ridge shifts over NorCal for the second half of the week for dry and unseasonably warm conditions, but lighter winds.

Extended discussion (Friday through Monday)

Upper ridging weakens Friday as short wave trough moves through the PacNW. Ridging then slowly rebuilds over the weekend into Monday resulting in a gradual warming trend. Models differ with offshore closed upper low as expected but all solutions continue dry weather. Near to slightly below high temperatures Friday slowly rise to slightly above normal over the weekend into Monday.