October 5, 2018 – Mostly dry Friday except for a few showers possibly northern mountains. Strong, gusty and dry north winds develop this weekend increasing fire danger. Temperatures a little below normal Saturday and Sunday remaining near to slightly below normal through the coming week. No precipitation expected through the extended period.
Discussion
Upper ridge moving quickly across the west coast this morning bringing fair skies to most areas. The clearer skies allowing temperatures to drop a few to several degrees from 24 hours ago. An upper trough pushing through the Pacific Northwest will bring a chance of showers to the northern mountains this afternoon and tonight. This trough is forecast to move into the Great Basin on Saturday bringing northerly flow aloft to the north state. Meanwhile, surface high pressure pushing into the Pacific Northwest will bring an increasing northerly surface gradient.
Combined vertical wind profile will bring increasing winds Saturday. By late afternoon, current forecasts push northerly winds up close to advisory but only locally. Daytime highs will warm some but still remain a little below normal. RH values will drop a bit Saturday but will remain elevated thanks to the recent rainfall. Decoupling will bring a slight drop off in wind overnight Saturday but winds will increase again on Sunday as gradients increase.
By mid day Sunday, winds throughout the central valley should top wind advisory criteria and will continue messaging for this probable wind event. Max temps Sunday will warm slightly more but still likely to come in a little below normal.
Strong winds and lowering RH will bring increased fire danger but RH values not expected to drop to particularly critical levels at this time. Upper ridge forecast to push in over the west coast on Monday bringing just a bit more warming with decreasing winds.
Extended Discussion (Tuesday through Friday)
Cool, dry northwest flow will develop next week between a deep trough over the Rocky Mountains and a high pressure ridge over the eastern Pacific. This will bring dry weather and below normal temperatures through mid week. Any precipitation is expected to remain well north and east of the region. Frosty conditions are possible overnights in mountain valleys and basins with clear skies and strong radiational cooling. Upper level ridging could bring warmer and continued dry weather into late next week.