Scientific Forecaster Discussion
fxus66 kmtr 262355
Area forecast discussion
National Weather Service San Francisco Bay area
455 PM PDT Wed Jul 26 2017
Synopsis...a gradual warming trend will get underway this
afternoon and continue into Friday. By Thursday and into the
weekend, afternoon temperatures will warm to above seasonal
averages for inland areas while coastal locations remain cool.
Above average temperatures are then likely to persist into early
Discussion...as of 1:59 PM PDT Wednesday...this morning's low
clouds have mostly mixed out for inland areas, revealing mostly
clear to clear skies across the region. Temperatures are generally
running within several degrees of what they were 24 hours ago at
this time. Afternoon high temperatures will range from the 60s to
perhaps as warm as the low 70s along the coast, and upper 70s to
low 90s for inland areas. Can't rule out a few areas that reach
the mid/upper 90s for parts of the southern Salinas valley,
Pinnacles National Park, and interior Monterey County.
An upper-level low just off the northern California coast will
push northeast over the next day and weaken as it continues into
the continent. By tomorrow we'll see 500 mb heights nudge upward
by 2-4 decameters as an upper level ridge expands over the Desert
Southwest. Along with height rises, models are advertising
warming in the low and mid-levels -- 850 mb temps are expected to
warm by 2-4 deg c over the next 24 hours. As a result, we'll see
warming conditions at the surface and a compression of the marine
layer. The challenging aspect of this is how warm will we exactly
get for Thursday and Friday. Looking at the many European model (ecmwf) ensemble
members, some of the warmest individual members are forecasting
the low 90s for tomorrow at San Jose (ksjc). With this in mind,
the official forecast for the next few days continues to follow
some of the warmest guidance. As for the potential heat levels,
there are some areas of moderate heat risk for the interior East
Bay and parts of the South Bay, but not quite enough coverage to
consider a heat advisory. We'll continue to monitor forecast highs
and heat levels over the next few days and make changes if
For the first half of the weekend, temperatures may cool by
a few degrees for interior locations as 500 mb heights fall with
a passing shortwave. Models begin to disagree with the placement
and strength of the ridge on Sunday, though overall begin to trend
500 mb heights back up into Monday. Into Tuesday and Wednesday
next week, models continue to advertise the upper-level ridge over
the southwestern US. This equates to more hot weather for
interior areas as we enter the beginning of August.
Aviation...as of 4:55 PM PDT Wednesday...for the 00z tafs.
Stratus is reaching back to the coastline with onshore breezes.
VFR continues at the area terminals, however cigs return tonight.
Lower level warming and compression of the marine layer may tend
to limit coverage of stratus tonight and Thursday morning
decreasing confidence in timing cigs somewhat. Gusty west to northwest winds
diminishing this evening.
Vicinity of ksfo...VFR with gusty west to northwest winds til 04z this evening.
Low cigs tonight, but timing is low confidence.
Sfo bridge approach...similar to ksfo.
Monterey Bay terminals...MVFR cigs redeveloping this evening, MVFR
cigs tonight. VFR returns by late Thursday morning.
Marine...as of 1:47 PM PDT Wednesday...winds will gradually
increase and transition to west and northwesterly across the
waters today. Most significant increases in wind speed will be
north of Point Reyes. Tropical disturbances in the Pacific will
generate a long period southerly swell that will reach the coastal
waters by Friday.
... Arena to Pigeon pt 10-60 nm from 9 PM
Small Craft Advisory...sf Bay until 11 PM
Public forecast: Rowe
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