Wind event winds down early, more concerns for Tuesday and Wednesday

October 28, 2019 – Wind event winding down early today, but still extreme fire weather danger due to dry air mass. Enhanced fire weather concerns possible again from Tuesday into Wednesday. Dry weather expected for at least the next week. Temperatures warming to a little above average by the end of the week.

Discussion

Water vapor satellite imagery shows the area of stronger subsidence has shifted south into SoCal. Skies remain clear across NorCal except for a few high clouds dropping southward. The north-south surface pressure gradient has relaxed considerably (KMFR-KSAC is currently around 7 mbs compared to over 16 mbs 24 hours ago) while the east gradient is hanging in around 7 mbs from KRNO-KSAC. Correspondingly, winds while still breezy are much lighter than early Sunday. Still seeing some northerly gusts around 20-40 mph along the western edge of the Sacramento Valley and northeast gusts of 25-45 mph across the foothills of eastern Butte County and across the higher elevations of the northern Sierra.

Winds decrease across the region this morning with just a brief break before another strong north wind event begins Tuesday and continues into Wednesday. Smoke from the Kincade Fire and Grizzly Fire may impact the Sacramento area and the northern San Joaquin Valley by later today and overnight tonight as flow briefly turns more westerly.

Ensemble means and latest ops runs indicate the next wave moving down from the north will be further east with the strongest portion over Nevada rather than NorCal. The north-south gradient (KMFR-KSAC) is forecast to top out “only” around 10 mbs, so while breezy to windy conditions are expected Tuesday into Wednesday, they will likely be much less impactful than this past weekend`s event.

That being said, any gusty winds on smoldering embers would not be welcomed, so Red Flag conditions are once again likely, and a new red flag will likely be raised later today. Pressure gradients and 925 mbs winds from the NAM support wind advisory criteria in the Sacramento Valley, especially the west side, and into Solano Co and southern Lake Co, and up into the foothills on the lee-side of the Coast Range. Also another round of 50 mph wind gusts likely around Jarbo Gap in the NE Sac Vly foothills. Winds will be increasing by late morning on Tuesday, with decreasing winds by later Wednesday.

High temperatures will return to a little above average by the end of the week. Mornings will be chilly in the mountain valleys and wind-sheltered portions of the Central Valley. Some patchy morning frost may even be possible along the eastern edge of the valley.

Extended Discussion (Friday through Monday)

Upper level high pressure ridge over the eastern Pacific and west coast will dominate the weather pattern through the extended period. Winds will generally be light under northerly flow around the high but subsidence under the ridge will keep humidity values on the low side for this time of year. Therefore, fire weather concerns will be somewhat elevated compared to early November normals with no precipitation in sight. Daytime highs Friday are forecast at near or slightly above normal with a slow increase going into the weekend.