NWS Forecast Area Discussion - San Francisco Area

FXUS66 KMTR 051212

Area Forecast Discussion
National Weather Service San Francisco Bay Area
512 AM PDT Tue Jul 5 2022

.SYNOPSIS...A mix of low and mid level clouds this morning with
the potential for drizzle along and near the coast. A gradual
warming and drying trend begins by midweek, however, below normal
temperatures persist today through Friday for the afternoon highs.
By Saturday, the region warms back to near to slightly above
normal conditions.

&& of 04:07 AM PDT Tuesday...Our forecast area
remains under the influence of an upper level low pressure system
centered off the coast of the Pacific NW. Yesterday`s weak cold
frontal passage, which brought some light rain to parts of our
CWA, was associated with that upper low. A mix of low to mid level
clouds continues to linger in our area. Some light precipitation,
likely drizzle, has occurred during the overnight shift with a
few hundredths at various gauges close to the coast in the past 6
hours. If you`re driving around early this morning near the coast,
you may detect some of this drizzle if low clouds are in your
area. Expecting some breezy conditions as some valley locations
(East Bay, Salinas Valley) get gusts from 20 to 30 mph this
afternoon into evening.

As that upper low lingers near the Pac NW this week, we won`t see
any major swings in temperatures. 850 mb temperatures will
gradually warm through the week going from around 12 to 15 degrees
C today becoming 17 to 20 degrees C by Friday. While overnight
lows remain within a few degrees of normal this week (50s to low
60s), the afternoon highs will range 5 to 10 degrees below normal
for much of the week with 60s to mid 70s closer to the coast and
mid 70s to mid 80s inland. The exception will be for southern San
Benito and Monterey counties where highs are forecast to warm into
the upper 80s to low 90s Thursday into Friday.

Over the weekend, that upper low weakens as high pressure builds
over the desert SW. The WPC 500 mb height cluster analysis lends
good confidence that the peak of the high pressure influence
should be around the Sunday/Monday timeframe. As the 500 heights
increase this weekend, the 850 mb temperatures are set to warm up
becoming 22 to 25 degrees C. That will translate to surface
daytime highs within a few degrees of normal for the weekend
(upper 60s to upper 70s near coast, 80s to mid 90s inland). The
high pressure continues to build into Monday putting much of our
CWA a few degrees above normal with more areas warming into the
mid to upper 90s in our hotter far inland locations. Even though
we do get warmer over the weekend, the ECMWF EFI (extreme forecast
index) is not highlighting a significant heat event. In terms of
Heat Risk, the majority of our forecast area will stay in Low Risk
through Saturday. On Sunday and Monday, the far interior areas
will be a mix of Low to Moderate Heat Risk which should prompt
those sensitive to heat to take precautions.

&& of 5:14 AM PDT Tuesday...For the 12Z TAFs. The
intermittent mix of mid and low clouds continues. Times of MVFR
CIGs look to last into the mid to late morning with light to
moderate winds through the morning. Consistent VFR returns with
mid clouds in the mid to late morning with winds becoming moderate
to breezy into the afternoon. Low clouds fill the bays and move
inland tonight, offering another batch of MVFR/IFR CIGs and patchy
fog. models are struggling on the exact times of these lowered
CIGs, the forecast follows the most likely scenario.

Vicinity of KSFO...Inconsistent times of MVFR with light winds
through the late morning then VFR for the afternoon with passing mid-
level clouds. Expect moderate to breezy westerly winds through the
day before easing into the night. Lower clouds look to begin fill
around the SF Bay in the late evening, leading to another night of

KSFO Bridge Approach...Similar to SFO.

Monterey Bay...Moments of MVFR with mist and patches of fog through
the mid to late morning morning. Winds will be light but become more
moderate for the afternoon. IFR CIGs with fog and mist are expected
to return for Tuesday evening as winds begin to reduce.

&& of 03:27 AM PDT Tuesday...Light winds over most
waters are expected with the exception of jets causing gusty winds
at the Monterey Bay and Big Sur Coast, causing dangerous
conditions for smaller vessels. A moderate  westerly swell at 9 to
12 seconds will arrive tonight. A light  long period southerly
swell also persists through the late week  with redeveloping wind
driven seas.





MARINE: Murdock

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NWS MTR Office Area Forecast Discussion