Area Forecast Discussion

KEY MESSAGES

- Seasonable temperatures and dry conditions persist over the weekend with generally offshore winds.

- Isolated mountain thunderstorm chances along the Sierra south of Highway 50 on Monday.

- Dry weather remainder of next week with gradual warming trend through the middle of the week.

DISCUSSION

This Weekend: Weak ridging aloft will continue to build in over the weekend with a deepening offshore trough then expected to approach the West Coast later in the day on Sunday. Resultant weather impacts through the weekend are expected to remain minimal with seasonable high temperatures in the 80s to low 90s and dry conditions. Light to occasionally breezy north to east winds gusting 15-20 mph at times look to shift toward onshore south to west winds on Sunday as the trough arrives. Low daytime humidity values and limited overnight recovery are anticipated today into Sunday morning with generally improving conditions later Sunday as onshore flow resumes.

Next Week: With ensemble guidance in general agreement on a more southerly track of the early to week trough, mountain thunderstorm chances continue to trend further southward as well. Isolated thunderstorm chances remain nonzero, but less than 10%, with highest potential now anticipated south of the Highway 50 corridor. While coverage will likely be limited at best, primary impacts from any thunderstorms that develop will be new fire starts from isolated lightning strikes and gusty outflow winds.

As the trough oscillates over SoCal and the Desert Southwest and generally weakens across the remainder of the week, interior NorCal is on track to remain underneath diffuse split flow aloft. This will generally usher in a period of lighter onshore winds, and with rising heights aloft, slightly warming temperatures into the mid to late week period. While there is uncertainty in the exact details of the warming next week, areas of Moderate HeatRisk will be possible in the Valley and Delta on Wednesday and Thursday. Heading toward the following weekend, offshore troughing is forecast to dig down from the Gulf of Alaska, inducing stronger onshore flow and introducing cooler temperatures, as well as a potential shift toward a more unsettled weather pattern.

AVIATION

VFR conditions expected through 18z Sunday. Winds at the TAF sites will mainly be less than 12 kts, but a few west-southwest gusts to 15-20 kts are possible in the Delta after 23Z Saturday. Downsloping winds through the Sierra will also gust 20-30 kts after 06Z Sunday. Winds are forecast to weaken after to 15Z Sunday.

STO WATCHES / WARNINGS / ADVISORIES

None.