Mike Pechner's Weather Blog

The Weather and You, by Meteorologist Mike Pechner
March 19, 2010

"FAST EXIT OF WINTER?"

A week ago this Friday, heavy rain pelted the Bay Area and Northern California while heavy snow snarled traffic in the High Sierra. The lingering effects of the storm continued into last weekend with morning frosts in the North Bay and chilly winds Saturday afternoon. Since then, Mother Nature has put the skids on winter, giving us an early preview of spring.

Temperatures have warmed each day going from below normal on Sunday to much above normal with a record high of 84 in Santa Rosa on Thursday.  Except for a brief period yesterday with morning coastal fog along the San Mateo County Coastline,  northerly to northeasterly winds have kept the onshore winds at bay,  allowing areas right near the ocean to warm up almost as much as the interior.  

For example, San Francisco has topped 70 degrees four days in a row. Thursday night was unusually warm for this early in the season in San Francisco and around the Bay.  Meteorologist Mike Polansky recorded a balmy 64 degrees in the Castro at midnight and was as warm as 61 at 4 .a.m. 

We also had a bizarre temperature spike around 11 p.m.  Fort Funston went up three degrees from 55 to 58, Cordelia from 64 to 68, Oakland from 64 to 68 and Richmond, the big winner going up five degrees from 63 to 68 in just a few minutes!  A wind shift occurred around 11 p.m. from the north to the northeast and the down slope, offshore winds produced the abrupt rise in temperature. 

It is also interesting to note that the air moving over the land and NOT coming in from the ocean was very dry and dew points were very low.  As a result, some wind-sheltered North Bay Valleys dropped into the low and mid 30's.  KCBS weather observer Larry Boggs reported a low of 36 Friday morning in San Anselmo after a high of 82 on Thursday, a spread of over 46 degrees!  John Dory Vineyards in Graton recorded a low of 34 and Valley Ford along the Marin-Sonoma County 35.

    There are indications from some of the medium range forecast models from the National Weather Service that a turn back to winter could happen as early as March 28th or 29th. This change in the current pattern is also supported by the European Forecast Center models. Much needed snow is expected in the High Sierra along with soaking rain here in the Bay Area. Even though water deliveries to growers have been increased, total snowfall and snow on the ground at Donner Pass is only at 100% of the long term average for this date.  Snow on the ground is at 88" and total snowfall for the season is 331" compared to the average of 328".  Average snowfall for the season is 450", so it is easy to see we have a way to go to have an average snowfall in the Donner Pass area.  In the meantime, temperatures will slide back to normal with increasing coastal fog. It should remain dry most of next week.   

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