The past two weeks has been cloudy, cool, and wet across most of the Bay area and Silicon Valley due to a change up in the weather pattern. A large trough or “dip” in the jet stream across the western United States has allowed a number of low pressure systems to move across the area bringing much needed rain and snow to higher elevations.
Here is a summary of what has fallen in the month of March across San Jose, San Francisco and Oakland courtesy of the National Weather Service office in Monterey California http://weather.gov/mtr:
San Jose: 0.73 inches
San Francisco: 2.21 inches
Oakland: 3.20 inches
Jet Stream Dynamics:
Through most of the winter, most of Northern California has enjoyed relatively mild and dry conditions unseasonable for the season. This was due in part to a strong large area of high pressure in the Pacific that kept low pressure systems away from the coast as well as the jet stream flowing north over the Pacific Northwest and British Columbia. Recently that jet stream has come south, and high pressure off the coast has moved south off of Mexico.
The long term weather forecast has more rain than sun in the forecast. The latest NAM and GFS weather models suggest a trough in the jet stream will continue to allow low pressure systems to flow down from the Pacific Northwest for quite a while. The next system will hit the Bay area just in time for the weekend. In addition to “short term” weather models, the National Center for Environmental Prediction (NCEP) is calling for April to have below average temperatures for Northern California and an equal chance for precipitation when compared to climatological values. Winter has hit us, just a bit late this year. Ski resorts and local plant life and flora are benefiting from the increase in precipitation as can be noticed when looking toward Mount Hamilton where the mountains have changed from a brownish dead color to bustling green color.
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