May 20, 2021
Very strong differences in pressure between San Francisco and Las Vegas continue. Couple that with strong jet stream energy above central California and you have the recipe for strong, gusty winds, especially along the center and west side of the valley. The current altimeter reading at SFO is 30.03 inches of mercury while Las Vegas’ reading has plummeted to 29.50. The center of circulation of the main low is currently over eastern Washington and Oregon with a trough extending southward into California. The freezing level above Oakland dropped from near 12,000 feet yesterday to 7,000 feet early this morning.
Models show the center of circulation moving southward over central California late tonight through Friday night. since this low developed over land, the amount of moisture is quite limited. Even so, lift along the Sierra Nevada will begin to increase the chance of showers and isolated thunderstorms later this afternoon, continuing through Sunday, mainly during the afternoons and evenings.
The chance of measurable rain on the valley floor remains very low. However, I’m comfortable in forecasting a risk of isolated light showers Friday and Friday night. On Saturday, this storm will begin to weaken and move into western Nevada. Models place the center of circulation over northeast Nevada Sunday. On Monday, a weak ridge of upper level high pressure will begin to build in from the west as temperatures climb back into the 80s. by Tuesday, most locations will be at least nearing the 90 degree mark.
A weak low is projected to move through northern California about the middle of next week, blunting any further warming.
Forecast: Mostly clear and much cooler today. Partly cloudy later tonight through Friday night with a small chance of widely scattered light showers. Mostly clear to occasionally partly cloudy Saturday. mostly clear Saturday night through Thursday of next week.
Temperatures: High temperatures today through Friday will only warm into the low to mid 70s, climbing into the upper 70s Saturday. Overnight lows will chill into the low to mid 40s tonight and again Friday night. in Kern County, lows will range from the mid 40s to near 50.
Next report: May 21/AM