Cooling trend continues today with below normal high temperatures this week. Chance of afternoon showers and thunderstorms over the mountains through Friday. Periods of gusty winds especially in the Delta and over higher terrain.
Discussion
Morning water vapor imagery shows the low off the coast remains on track and continues its drift southward this morning through most of today before beginning to approach SoCal early Tuesday morning. This will help feed moisture into the area and will see a repeat of afternoon and early evening showers and isolated thunderstorms.
Latest NBM guidance indicates coverage decreasing after today as convective indices lower in strength and move southward Tuesday with the aforementioned low, albeit continued slight chances south of Hwy. 50.
Wednesday will see an increase in shower and isolated thunderstorm coverage again from Redding to Tahoe, then moving down the Sierra through Thursday as the low moves through Southern California combined with an upper level low moving in from the Pacific Northwest.
Delta breeze continues around 15-20 kts with elevated winds at higher terrain. Wednesday shows the chance for breezy conditions across the Valley as the low from the Pacific Northwest drops down with gusts up to 20 mph and higher along terrain.
Winds do look to turn northerly-northeasterly across the Northern Sacramento Valley Wednesday evening through Thursday afternoon along I-5 but remain below any critical indices, especially given the lower temperatures and remaining moisture over the area limiting the threat of enhanced fire weather conditions.
Extended Discussion (Friday through Monday)
By Friday, the aforementioned trough will begin to lift northeast, leaving behind dry northwest flow across northern CA, leaving the region dry. Clusters and ensembles begin to diverge slightly beyond Friday with how quickly the trough will shift eastward, being replaced with increased heights/weak ridging. Even so, clusters do begin to become in alignment on the eventual ridge building across the Rocky Mountain region with a strong anomalous low developing off the PacNW coast.
This pattern will result in subtle increase in temps Friday and Saturday. Confidence on when and how much the upstream low may impact interior northern CA next weekend is fairly low considering timing and location discrepancies with the low center.
Even so, looking at the NBM box and whisker plots, temperatures may continue to be mild with highs in the low 80s or as cool as the low to mid 70s by late weekend. Stay tuned!