From the National Weather Service:
“Area Forecast Discussion
National Weather Service San Francisco CA
839 am pet Fri apr 28 2006
.Discussion…the second half of April has quickly taken northern and central California from winter to summer…as the eastern pacific subtropical high has bulged northward over the past several days. The lingering upper low which brought instability and a few showers/thunderstorms to southern California yesterday has since kicked eastward into Arizona and new Mexico. This will leave our district with the familiar low clouds and fog spreading inland each night…retreating to the coast by midday each day…with near normal temperatures throughout.
The warm air aloft has developed a strong marine inversion…and as a result widespread stratus has developed over the coastal waters. The marine layer is about 2200 ft deep per the Fort Ord profiler and 1700 ft deep per the bodega bay profiler. Surface gradients are onshore…+1.6 MB from KSFO-KSAC …causing a gusty onshore flow to persist all last night through the golden gate. The onshore gradients will only intensify this afternoon as the inland areas warm up…so expect the low clouds to linger near the coast for much of the day. In fact…the stratus will probably begin to come back into San Francisco bay by late this afternoon.
All this means locations near the coast and bays should be a few degrees cooler than Thursday. However…with 850 mb temperatures hovering near +18 deg c…inland spots should have no problem warming back into the 80s with a few of the warmer locations likely pushing 90 degrees this afternoon. Will update the forecast to cool off some of the coastal/bay locations but otherwise the forecast looks good.
This pattern will likely persist well into next week as the GFS/Euro keep a strong SFC high over the eastern pacific through next Wed/Thu. The migratory storm track has finally been pushed northward into Canada…along with the chances for significant rain. The strong upper ridge will weaken slightly over the next 48-72 hours… Resulting in slightly cooler temperatures inland. Coastal stratus will likely stick around for the foreseeable future as a strong marine inversion remains in place. Welcome back to coastal California summer…it’s been a long time in the making.”