November 11, 2018 – Dry weather continues with cool nights and near to above normal days through the week. Critical fire weather conditions continue through Monday morning with breezy winds and low humidity. Widespread smoke from the Camp Fire will continue to impact much of the area.
Discussion
The area remains on the east side of a strong eastern Pacific Ridge. A trough dropping into the Great Basin is bringing an increasing surface pressure gradient. Northerly winds are starting to increase this morning from north to south across the forecast areas, with gusts at 3 am to 31 mph at Redding, 22 mph at Vacaville and Marysville. These spots are quite mild due to the wind, with Redding a mild 58 degrees, Vacaville 61. Locations to the south have much lighter winds and so are much cooler, with temperatures dropping into the 30s. This will make a big contrast in temperatures for low temperatures this morning and through the day. Valley locations to the north of the smoke could reach the low 70s, while areas to the south should remain in the 60s.
Northerly winds and very low humidity are bringing another round of very high fire danger to the area. Winds in the mountains are already gusting to 40 to 60 mph on some mountain peaks. Winds should peak in the morning hours, with a Wind Advisory remaining in effect through noon today. Humidity is extremely low, with overnight recovery down in the teens in many locations. This along with the wind and near record dry fuels is bringing critical fire weather conditions, which are expected to continue into early Monday. A Red Flag Warning continues for much of the area through that time period.
In addition to warming temperatures and bringing fire danger, the winds are beginning to clear smoke, especially over the northern Sacramento Valley. Light winds and a strong inversion have brought dense smoke to ground level, bringing poor visibility and bad air quality. Some improvement is expected to gradually spread southward down the Sacramento Valley, though areas north of I80 will probably get more improvement than areas to the south, which will see as much wind.
No precipitation is expected across interior NorCal as high pressure remains in control of the region. Daytime highs will depend on how much smoke blocks the sun. Morning lows are anticipated to be in the 30s to mid 40s across the Valley, with some forst locally possible. Lows will be in the 10s to low 20s across mountain basin locations.
Extended Discussion (Thursday through Sunday)
Broad upper ridge forecast to continue across the region later in the week maintaining dry weather with mild days and cool nights, and no strong wind events are expected. Upstream trough forecast to split across the eastern Pacific with most of the energy forecast to dig southeastward toward Baja and SoCal late next weekend. Confidence in details remains low.