August 17, 2019 – Temperature will cool over the weekend with below average temperatures by Sunday.
Warming slowly through next week to a little above average with triple digits in the Valley by mid-week. No precipitation expected over interior NorCal through the extended period.
Discussion
Relative to last night, most locations have seen a notable decrease in overnight temperatures, generally in the 5 to 10 degree range. The erosion of the Four Corners ridge has allowed mid-level heights to lower over northern California. Further amplification in the northern stream flow this weekend will allow temperatures to move below average by Sunday. Valley highs will range from the mid/upper 80s Sacramento southward to the low 90s over the northern Sacramento Valley. Such readings should continue into Monday, thus offering some relief after multiple days in the triple digits.
The shift in the pattern will also support a significant uptick in the Delta breeze. Through Monday morning, sustained wind speeds around the Delta region should be in the 25 to 35 mph accompanied by higher gusts. The resultant southerly flow across the Valley will offer the noted relief from the earlier week hot temperatures. Given the enhanced marine influence to the air mass, there will likely be an increase in low clouds extending out of the Delta the next couple of nights/mornings. This is supported by NAM model soundings as well as the HREF probabilities.
Looking beyond Monday, a strengthening trough off the coast will build heights across the state by Tuesday. This ultimately brings temperatures to near average after a multi-day cool down.
Extended Discussion (Wednesday through Saturday)
Ensembles show high pressure peaking over the area around mid- week before weakening slightly as a weak trough develops along the West Coast later next week.
Temperatures will be around 5-10 degrees above average for late-August mid-week, cooling to slightly above average toward the end of the week.