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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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