February 9, 2020 – Cooler with windy conditions today. Dry next week except a threat of showers late Thursday into Saturday, mainly over mountains.
Discussion
Upper low digging down the Sierra Nevada range this morning. 88-D radar showing little in the way of returns although Highland Meadow reported some light precip earlier. Little to no precip expected over the Northern Sierra as system drops south during the day. Strong northerly flow aloft behind this feature is combined with 1041 MB EPAC surface high building through Oregon into the Great Basin. This resulting in breezy to windy conditions over portions of interior NorCal today.
Strongest wind currently being observed in the Delta area. Guidance suggest wind in this area will continue to increase this morning, ramping up into low end high wind criteria. Given non-prevailing direction, increased potential for downed trees in this area. Will embed a high wind warning for this area today with a period of sustained wind 30 to 45 mph with local gusts up to 60 mph possible. Strong wind also progged in western portions of the Sacramento Valley extending into the Coastal Range, and in the Northern Sierra.
Pressure gradient weakens this evening in the Central Valley, but wind remains gusty in portions of the Coastal Range and Sierra Nevada overnight into Monday.
Breezy conditions again likely over portions of interior NorCal Monday, but wind speeds expected to remain below advisory criteria. AMS warms Monday into Tuesday as upper ridging builds inland. High temperatures by Tuesday expected to be up into the lower 70s for northern portions of the Sacramento Valley, which is about 10 to 15 degrees above normal. Mostly 50s and 60s forecast for the foothills and mountains.
Upper ridging weakens Wednesday as short wave trough moves southward through it over NorCal. This will result in minor synoptic cooling but continued above normal temperatures.
Extended Discussion (Thursday through Sunday)
Broad upper ridging across the eastern Pacific will continue dry conditions and well above average temperatures for Thursday. Valley and Delta highs should stay in the mid to upper 60s through Thursday with mostly sunny skies.
By late Thursday, the ridge is forecast to shift eastward in response to a trough slipping down from the Pacific Northwest. The current track of this system will bring a slight chance for mountain and foothill showers through Friday, while the rest of the area stays dry. Light mountain showers should wind down Friday night into early Saturday.
Models and ensembles are trending towards another shortwave passing through later Saturday through Sunday. Even some Valley precipitation is possible, although rainfall amounts look fairly light at this point. Forecast mountain snowfall also currently looks fairly light with limited impact, but some ensemble members hint at something more significant. This will have to be monitored closely, due to busy travel expected over the holiday weekend. Snow levels are expected to be around 4000-5000 feet.