430
FXUS66 KMTR 212346
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
446 PM PDT Fri Jul 21 2017

.SYNOPSIS...As a ridge of high pressure builds into our region
temperatures will warmer into the weekend. Temperatures will
moderate next week as the ridge progresses to the east.

&&

.DISCUSSION...as of 01:42 PM PDT Friday...This morning`s stratus
was quick to mix out and transition to mostly clear skies across
the region this afternoon. Compared to 24 hours ago, temperatures
at most Bay Area airports are running between 2 and 4 degrees
warmer. These trends can be translated to this afternoon`s highs
as we begin a warming trend into the weekend. Friday`s highs along
the coast will range from the 50s to 60s and highs inland will be
anywhere from the mid 70s to 90s.

A building upper level ridge is largely responsible for the
warming temperatures. 500 mb heights currently sit around 589 to
590 dam and will trend upward to 593 to 594 dam over the weekend.
Additionally, 850 mb temps will nudge from about 20 deg C to 23
deg C from today to Saturday, per the 12Z ECMWF. At the surface
this will translate to widespread 80s and 90s for inland
communities on both Saturday and Sunday. Right now, there are no
indications that this weekend`s temperatures will approach prior
heat event levels. As mentioned in previous discussions, the
warmest ECMWF ensemble members remain cooler than the observed
highs from July 7-8 when many Bay Area interior locations
surpassed the century mark. Since the expected heat risk values
remain in the low to moderate range, don`t anticipate on launching
any heat- related headlines given the current forecast. Coastal
locations are forecast to remain cool with highs generally in the
60s to 70s.

Models are in fair agreement in advertising an upper level low to
approach the northern California coast early next week. As a
result, temperatures for interior areas will begin a cooling trend
on Monday and continue into the middle part of next week. By this
point, models are trying to suggest midlevel moisture advection
into parts of central California. Unfortunately, models have been
inconsistent from run-to-run and therefore confidence remains low
for shower and thunderstorm potential at this time. For now,
probability of precipitation is less than 10 percent. We`ll
continue to monitor moisture trends in the models and adjust the
forecast accordingly.

&&

.AVIATION...as of 4:45 PM PDT Friday...Similar conditions to
yesterday with the marine layer near 1000 feet and a strong n-s
gradient keeping skies clear along the coast. Stratus clouds will
reform late along the coast and will spread into the MRY Bay Area
terminals and through the Golden Gate into OAK and possibly SFO
early Saturday morning.

Vicinity of KSFO...VFR. Possible MVFR cigs between 13Z and 16Z.
West winds gusting to 28 kt through 04Z.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...IFR cigs after 10Z.


&&

.MARINE...as of 01:30 PM PDT Friday...Gusty northwesterly winds
will continue into Saturday before  decreasing somewhat during the
remainder of the weekend as high  pressure off the California
coast begins to weaken.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...SCA...Mry Bay until 9 PM
             SCA...Pt Reyes to Pigeon Pt 0-10 nm until 9 PM
             SCA...Pigeon Pt to Pt Pinos 0-10 nm until 9 PM
             SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm

&&

$$

PUBLIC FORECAST: Rowe
AVIATION: W Pi
MARINE: Sims


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