Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
FXUS66 KMTR 300501
Area Forecast Discussion
National Weather Service San Francisco Bay Area
1001 PM PDT FRI JUL 29 2016
.SYNOPSIS...Typical summertime conditions will continue over the
next several days with low clouds/fog and cool temperatures near
the coast along with warm conditions inland. A gradual cooling
trend is forecast for inland areas from Saturday through Monday as
an upper level trough develops across the Pacific Northwest and
northern California. Smokey conditions will continue over
portions of the Monterey Bay Area northward into the South Bay.
.DISCUSSION...As of 9:00 PM PDT Friday...There has been very
little change in our weather from yesterday to today. Afternoon
highs today varied by more than 40 degrees across the San
Francisco Bay Area. For instance, the high in foggy Half Moon Bay
today was 60 degrees, 42 degrees cooler than the 102 degree high
posted in Livermore. Across our entire forecast area the high
temperature spread was even larger, ranging from a chilly 56 at
Ocean Beach in San Francisco to 110 at Pinnacles National Park (a
54 degree difference).
An upper level trough is forecast to gradually develop over the
Pacific Northwest and far northern California through the weekend
and into the early part of next week. This will result in modest
cooling for inland areas by Sunday and Monday as the marine layer
deepens slightly. In addition, southerly flow which has already
developed aloft is forecast to develop near the surface by
tomorrow morning, especially for areas near the coast. These
southerly winds will bring about additional cooling for some
coastal areas and valleys that open to the south. Look for
temperatures by Sunday and Monday to be 5 to 10 degrees cooler for
most inland areas, and locally as much as 15 degrees cooler. Just
how much cooling occurs will depend on just how much the marine
layer deepens, which is always a challenge to forecast.
Smoke from the Soberanes Fire is drifting the northeast this
evening, across the northern Salinas Valley and southern Santa
Clara Valley. Winds are forecast to continue out of the southwest
through the weekend, perhaps backing a bit more to due south at
times. Thus, areas to the north and northeast of the Soberanes
Fire will probably continue to be affected by smoke through the
One additional item to watch over the next few days is mid level
moisture and instability that will be increasing across southern
California over the weekend. The 00Z NAM brings some of this
increased mid level moisture and instability as far north as
Monterey County on Monday. If the NAM were to verify, there would
be concern for isolated high-based convection across the southern
part of our region early next week. However, the GFS keeps nearly
all moisture and instability well to our south and east and even
the NAM solution shows very nominal values of mid level moisture
and instability. So, the potential for isolated thunderstorms
across the southern part of our area next week appears to be very
low and there is not sufficient confidence to add it to the
forecast for now.
Very little change is anticipated going through next week, with
temperatures expected to be near normal.
.AVIATION...as of 10:01 PM PDT Friday...A strong mid-upper level
high center will remain near KLAS while a weak and dry surface-mid
level low center develops over the EPAC and overlaps the coastal
waters tonight and Saturday. Onshore winds persist with a marine
layer 1,000 feet deep. Onshore winds will combine with southerly
flow over the inner coastal waters while southerly flow aloft
persists area-wide in between aforementioned high and low centers
this weekend. Areas of haze and smoke persist.
Subtle 925 mb level cooling is forecast into early Sat morning
followed by steadier cooling Saturday-Sunday likely causing the
marine layer to remain nearly unchanged in depth tonight then
deepen Saturday-Sunday. IFR and LIFR cigs and vsbys due to stratus
and fog along the coastline persist with intrusions into the San
Francisco Bay and northern Salinas Valley late tonight and Saturday
morning, more in the way of stratus and fog moving inland is
anticipated Sat night and Sunday.
Vicinity of KSFO...W-NW winds near 10 knots tonight, resuming to
gusty west winds to 20 knots Saturday afternoon and evening. VFR.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...IFR/LIFR tonight, light onshore winds. MVFR/VFR
returns by late Saturday morning.
.MARINE...as of 9:17 PM PDT Friday...Northwest winds will persist
over the northern outer waters while southwest to south winds
develop over the remainder of the coastal waters this weekend.
Onshore winds will continue into the bays strongest each afternoon
and evening. A longer period southerly swell will mix with
northwesterly swell through this weekend.
.Tngt...SCA...SF Bay until 11 PM
PUBLIC FORECAST: Dykema
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