Cooler and more unsettled weather thru mid-week with a chance of showers and thunderstorms. Potential for Burn Scar impacts/Debris Flow, namely over the Park Fire burn Scar this evening into Monday morning. Confidence continues to increase in another weather system moving through interior NorCal Wednesday, with widespread showers and thunderstorm chances (10-30%) and gusty winds. Cooler high temperatures will persist until next weekend, where we will warm back up into the low 90s.
Discussion
Clouds and a few light showers are beginning to work their way southward into far northern California along the front early this morning. To the south ahead of the front, skies remain clear with relatively mild temperatures (readings in the mid 60s to mid 70s through much of the Central Valley outside of areas influenced by the Delta Breeze).
Northwest California will continue to see the best chance for showers today as short-wave energy digs the trough southward offshore. The HREF shows the best potential for showers and thunderstorms over northern portions of the Coast Range up into Shasta County later today as moisture and instability pool over the north end of the valley ahead of the trough. Later tonight and Monday, shower potential is likely to spread south and east over the remainder of the forecast area with the upper low, also bringing potential for a little snow over the higher elevations of the northern Sierra (recent warm weather may alleviate potential for much accumulation on road surfaces).
QPF is generally expected to remain under 0.25″ with some mountain areas possibly seeing up to 0.50″ (locally higher with thunderstorms in the Coast Range and Shasta County).
Later Monday into Tuesday we’ll likely see a brief break in showers before another system drops down from the north on Wednesday bringing renewed shower and thunderstorm chances.
Temperatures will also be considerably cooler through mid-week with readings expected to be around 10-20 degrees cooler compared to Saturday’s highs.
Extended Discussion (Thursday through Sunday)
Models differ with progression of upper low through CA Thursday with NBM leaning more towards slower EC. As a result, threat of showers advertised to continue over the Sierra Nevada Thursday. Expect mainly liquid precip as snow levels climb above 10k ft by Thursday afternoon. AMS warms Thursday as upstream EPAC upper ridging begins to build inland.
Highs forecast in the low to mid 80s in the Central Valley with highs in the mountains and foothills ranging from the upper 40s at the highest elevations to 70s in the foothills.
Some locally gusty northerly wind possible Thursday as stronger winds aloft mix to the surface. Warming trend continues into the weekend as heights trend up. Highs expected to be near to slightly above normal by Sunday.