Area forecast discussion 
National Weather Service San Francisco Bay area 
946 PM PST Thu Dec 8 2016 


Synopsis...look for scattered showers to continue into Friday. 
Widespread rain will return starting late Friday as a front 
approaches our region. Rain will changer over to showers late on 
Saturday with drier conditions forecast for Sunday. More systems 
are on tap starting the middle of next week. 


&& 


Discussion...as of 9:00 PM PST Thursday...balmy conditions exist 
across the region this evening with temperatures running in the 
lower to mid 50s across the northern half of the district and mid 
to upper 50s south of the San Francisco Bay. With dew points in 
the upper 40s to mid 50s humidity values are currently in the 80 
to 100 percent range. The moist boundary layer will persist 
through tonight as a result of the widespread rainfall that fell 
earlier today. Rainfall has tapered significantly since this 
afternoon. Kmux Doppler radar continues to pick up remnant 
scattered showers moving across the region. With little in the way 
of dynamic forcing precipitation has been primarily terrain 
driven. Accumulations over the last 6 hours have been anywhere 
from a tenth or less over low lying areas and over inland areas with 
higher elevation locations and spots along the coast picking up 
anywhere from 0.10" to upwards of 0.40". Three Peaks and Chalk 
Peak both located around 3400 feet in Monterey County picked up 
0.87" in the last 6 hours. Anderson Peak, Mining Ridge and the Big 
Sur RAWS picked up 0.55", 0.48" and 0.48" respectively. 


Scattered showers will continue through tonight with the next 
round of rain forecast to move into the region Friday morning. 
Models indicate precipitable water values around 1.25" moving in 
over the Big Sur coast on Friday with showers continuing 
elsewhere. An approaching cold front will move in over northern 
California Friday night and slide south across the North Bay 
overnight and subsequently toward the Monterey Bay area on Saturday. 


From previous discussion...all of the models do indicate widespread 
rainfall with an associated frontal boundary near the Bay area. 
Rain will spread to the south and eventually impact the entire 
region. Rain will again taper off to showers later on Saturday 
with just isolated showers expected on Sunday. 


Rainfall totals from now through Saturday are similar to the 
values that we received from yesterday into today. In general, 
1/2" to 1.25" for most urban spots with 1.5" to locally more than 
3" for the coastal ranges. Rainfall should be the heaviest late 
Friday into the first half of Saturday, although amounts are not 
expected to lead to Hydro issues except for less than ideal 
driving conditions. Pre-frontal south to southeast winds will also 
increase late Friday into Saturday. Urban locations will see gusts 
to 25 miles per hour Saturday morning with higher elevation spots likely to 
see local gusts to 35 miles per hour. 


Unsettled weather will remain in the cards through the end of 
next week as the zonal flow keeps the moist air in place. CPC 6 to 
10 and 8 to 14 day outlooks (out to December 22nd) both favor 
above normal rainfall. In fact, their outlooks are trending wetter 
compared to the previous versions. 


&& 


Aviation...as of 9:45 PM PST Thursday...moist onshore flow will 
continue through the forecast period. Shower activity will mostly be 
confined to the coastal mountain ranges, although isolated showers 
may impact the terminals from time to time. More widespread rain 
is due in by late Friday as a weather disturbance approaches the 
coast. In the meantime, look for continued widespread MVFR/IFR 
ceilings along with locally reduced visibilities. Winds will 
mostly be light southerly. 


Vicinity of ksfo...MVFR ceilings through the forecast period with 
IFR ceilings possible at times, along with MVFR visibilities. 
Showers expected in the vicinity of the terminal through much of 
the forecast period and a few brief light showers may reach the 
terminal from time to time. More widespread rain will likely 
develop by Friday evening. Winds light from the south and 
southeast through the period. Forecast confidence is moderate. 


Sfo bridge approach...similar to ksfo. 


Monterey Bay terminals...MVFR/IFR ceilings through the forecast 
period with MVFR visibility possible later tonight and into Friday 
morning. Rain showers in the vicinity. Winds light from the south 
and southeast. Forecast confidence moderate. 


&& 


Marine...as of 8:51 PM PST Thursday...generally light to 
occasionally moderate southerly winds will persist through Friday. 
Southerly winds will briefly increase Friday night ahead of a 
frontal boundary. Winds will then turn northwest in wake of the 
frontal boundary this weekend. A dominate westerly swell train 
will move across the waters through the remainder of the work 
week. 


&& 


Mtr watches/warnings/advisories... 
... 


$$ 


Public forecast: CW 
aviation: dykema 
marine: dykema 




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