Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
1051 PM PDT Thursday may 28 2015
Synopsis...a modest warming trend remains on track through
Saturday as a ridge of high pressure continues to build along the
West Coast. This warming trend will be most apparent inland.
Cooler temperatures are expected beginning Sunday as a low
pressure system approaches the coast. There is a slight chance of
showers across the North Bay from late Sunday into Monday with
night time coastal drizzle expected.
Discussion...as of 8:58 PM PDT Thursday...temperatures finished
off several degrees warmer than yesterday with inland temperatures seeing
the greatest warming. Our warm spot today was Parkfield in
southern Monterey County with a high of 91 degrees. Coastal
locations actually experienced slightly cooler temperatures due to
coastal low clouds as well as a slightly more robust seabreeze.
The slight warming trend experienced over inland areas today was
sparked by a ridge of high pressure currently building over the
region. This high has also compressing the marine layer down to
around 1500 feet this evening. Satellite imagery continues to
Show Low clouds hugging the coast at this hour with some inland
penetration through coastal gaps and valleys. While the district
will awake to widespread stratus a shallower marine layer will
likely lead to an earlier burn off time.
Little change in the weather is expected Friday and Saturday as
the ridge remains over the region. However a change in the pattern
is on the way. Two low that are spinning near 39n 138w and 40n
150w are forecast to merge before making their way east. This
system is forecast to reach the coast Sunday bringing a chance of
showers to the North Bay. A slight chance of light showers or
drizzle is possible from the Bay area south. However showers will
likely be in the form of patchy drizzle along the coast to hit-or-
miss showers. Cooler temperatures are also in-store into early
next week as the trough passes through the region.
Forecast remains on track...no updates at this time.
Aviation...as of 10:50 PM PDT Thursday...widespread IFR ceilings
forecast for Thursday night into Friday morning. The marine layer
depth is expected to continue to trend down into Friday
morning...and so expect slightly earlier clearing on Friday
compared to Thursday. Otherwise...moderate onshore flow should
mean a relatively early return of low ceilings late Friday afternoon
and Friday evening.
Vicinity of ksfo...IFR ceilings through 18-19z. VFR thereafter with
IFR ceilings returning by 02z Friday evening. West winds increasing to
18g25 kts by late Friday afternoon. Moderate confidence.
Ksfo bridge approach...similar to ksfo except clearing slightly
earlier on Friday.
Monterey Bay area terminals...widespread IFR ceilings continuing
through much of Friday morning. MVFR ceilings may persist through the
day Friday at kmry. Light to moderate onshore winds.
Beaches...as of 10:50 am PDT Thursday...a westerly swell of 5 to
7 feet with a period around 14 seconds will continue to move into
the coastal waters today. The combination of this swell and
generally weak onshore winds will result in an increased risk of
strong rip currents along area beaches through this evening.
Marine...as of 9:00 PM PDT Thursday...generally light northwest
winds are forecast through the weekend. Locally stronger wind
speeds will occur across the northern San Francisco Bay...off of
the Sonoma coastline...and along the Big Sur coast during the
afternoon and evening hours. A cold front will move through the
northern waters late Sunday and Sunday night. Stronger northwest
winds will develop behind the front next week.
... Pinos to pt Piedras Blancas 0-10 nm
Public forecast: CW
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