Warming and drying trend begins Monday with triple digit heat possible in the Central Valley by late-week. Widespread triple digit temperatures with moderate to high Heat Risk Thursday – Saturday.
Discussion
Showers have cleared out of the region early this morning with lingering clouds draped across northern California as seen on satellite. Relative humidity values are high with much of the Sierra reporting near saturation. Some areas of low clouds can be teased out from nighttime satellite imagery, generally in the motherlode foothill valleys and mountain valleys.
Temperatures are also mild, with most locations in the 60s in the Valley, 50s in the foothills and 40s in the mountains. Generally quiet weather with a warming and drying trend is forecast for interior northern California through mid-week. Generally light winds are also expected for most, with locally breezy winds at times through the Delta.
Ensemble guidance continues to show ridging building over northern California into Tuesday before shifting and becoming more amplified over the Desert Southwest. This will lead to warming temperatures with an onshore gradient over northern California. A weak shortwave is also forecast to graze northern California late Tuesday that could lead to a stray light shower reaching Shasta County as depicted by the NAMnest.
However, with building high pressure forecast over the region, highs will be on the increase with widespread highs in the 90s across the Valley on Tuesday. Similar highs are forecast on Wednesday with dry weather. By Thursday, broad upper-level ridging set in over the Desert Southwest with the western end of the ridging over California. Highs are forecast to near the century mark for much of the valley with moderate to locally high heat risk in the Valley.
Extended Discussion (Friday through Monday)
Ensembles and clusters show upper ridging dominating the synoptic weather pattern for the end of the work week before becoming more zonal over the weekend. Friday looks to be the warmest day with moderate to high heat risk for many. EFI continues to highlight warm overnight and daytime temperatures into Saturday morning.
Forecast Highs for Friday in the Valley are in the triple digits and could be close to 105 degrees for some locations. Slightly lower temperatures are expected Saturday as a low pressure system to our northwest acts to flatten the ridging over the region. There is also some indication a weak system could bring some shower chances to far northern California over the weekend with minimal accumulations expected.