FXUS66 KMTR 191135

Area Forecast Discussion
National Weather Service San Francisco Bay Area
435 AM PDT Tue Jun 19 2018

.SYNOPSIS...Temperatures will warm throughout the interior this
afternoon as high pressure begins to build over the southwestern
United States. Little day-to-day change in highs are expected from
Tuesday to Wednesday as the ridge flattens before a more noted
warming trend develops late in the week and into the weekend with
hot temperatures forecast for inland areas.


.DISCUSSION...as of 2:52 AM PDT Tuesday...Infrared satellite
imagery reveals areas of coastal stratus across parts of the San
Francisco Bay Area and central California coast this early Tuesday
morning. According to the Fort Ord profiler, the marine layer
depth has compressed to around 1,200 to 1,500 ft deep, whereas
yesterday morning at this time it was around 2,500 ft. A
consequence to a more compressed marine layer is the increased
possibility of localized fog along the coast through sunrise. If
you encounter reduced visibilities on your Tuesday morning
commute, be mindful of your speed, following distance, and ensure
your headlights are on. This compression of the marine layer is
largely a result of a departing upper level low that has been
replaced with a building upper level ridge. This ridge will be the
main focus for the extended forecast as temperatures are forecast
to rise through the rest of the work week and into the weekend.

For the short-term, high temperatures this afternoon are expected
to trend upward across the interior anywhere from ~ 4 to 8
degrees from Monday. Again, this is a result of the building upper
level ridge that is currently off the Baja California coast. The
ridge's influence is beginning to show in the Oakland upper air
balloon launches: from 12Z June 18 to 00Z June 19, 500 mb heights
have risen from 579 to 583 decameters, and 850 mb temps have
bumped up from 13.2 to 15.0 deg C. Despite little day-to-day
change from Tuesday to Wednesday, the upward trend in heights and
temps will really ramp by by the end of the week with forecasted
500 mb heights expected to reach 592+ decameters by the weekend
over the Bay Area with 850 mb temps rising to 22+ deg C. At the
surface, these values will translate to widespread 90s and triple
digits for inland communities. Official high temperature forecasts
over the weekend could perhaps be too low for some locations as
models can (and have) struggled to properly capture warming for
parts of our region. For example, the official forecast high on
Saturday for San Jose is 93 degrees, but some of the hottest
members of the ECMWF Ensemble Prediction System are advertising
upper 90s/low 100s in San Jose. We'll continue to monitor the
latest deterministic and ensemble guidance over the next few days
and adjust the forecast accordingly. Heat impact levels are
expected to at least reach the moderate (orange) category this
weekend, but again will have to monitor for changes over the next
few days. Temperatures along the immediate Pacific coast are
expected to remain fairly comfortable into the weekend with highs
generally in 60s to low 80s. The ridge is expected to weaken
heading into the beginning of next week, and will allow for
temperatures in the interior to begin a cooling trend.


.AVIATION...As of 04:35 AM PDT Tuesday...For 12z tafs. The marine
layer currently remains at around 1000 ft with cigs ranging from
as low as 100 ft at KMRY to up to 1100 ft at KSJC. IFR cigs are
expected to continue into the morning with clearing between 16z-
18z. There is a chance cigs could raise a bit after sunrise. VFR
conditions are expected this afternoon and evening before low
clouds return late tonight. Generally light winds through the
period with onshore winds this afternoon 10 to 15 kt.

Low confidence on clearing times.

Vicinity of KSFO...IFR cigs through 16z-17z. VFR this afternoon
and evening before IFR cigs return late tonight. Breezy onshore
winds this afternoon with gusts 20-25kt.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...LIFR cigs through sunrise, potentially
then rising to IFR. Clearing is expected between 17z-18z. VFR
conditions this afternoon before IFR cigs return tonight.
Generally light winds through the period.


.MARINE...as of 2:44 AM PDT Tuesday...Light to moderate northwesterly
winds will persist across the coastal waters through mid week
before winds increase. Gusty winds are expected this afternoon for
the near shore waters as well as the San Francisco and Monterey
Bays. Seas will remain relatively light with a mixed northwest and
southerly swell.


.Tday...SCA...Pt Arena to Pt Reyes 0-10 nm from 12 PM
SCA...Mry Bay from 2 PM
SCA...Pigeon Pt to Pt Pinos 0-10 nm from 2 PM
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm from 2 PM
SCA...SF Bay from 12 PM




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