Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
915 am PDT Thursday may 28 2015
Synopsis...a modest warming trend is expected through Saturday as
a ridge of high pressure builds 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.
Discussion...as of 9:15 am PDT Thursday...the current visible
satellite image is showing low clouds present in all of our areas
inland valleys as well as San Francisco and Monterey bays. The
Fort Ord profiler is indicating that the marine layer has reached
a depth of 2000 feet which is pretty typical for this time of
year. Unfortunately, this deep marine layer and gentle onshore
flow spells another late cloud burn off for most areas with
coastal area such as Monterey unlikely to see the sun today.
The current satellite water vapour image is showing a low pressure
system centered around 40n 150w this morning with a ridge of high
pressure positioned along the central and Southern California
coast. The 0000z European model (ecmwf) and 1200z gfs40 have initialized well with
the current synoptic pattern and maintain a weak ridge of high
pressure over the area through at least Saturday. As a result of
this ridge of high pressure expect temperatures to be closer to
normal seasonal values through Saturday.
Both models also drive the previously mentioned low pressure system
towards the coast over the next few days. The low will begin to
impact the area Sunday with cooler temperatures and coastal
drizzle. A slight chance of showers over the North Bay will also
be possible Sunday evening. The low will quickly pass to the
northeast by Monday with quazi-zonal flow filling in behind. This
quazi-zonal flow will maintain mild temperatures through the
upcoming work week.
Aviation...as of 5:15 am PDT Thursday... high pressure aloft
leading to subsidence over marine layer compressing moisture
towards surface. This is resulting in widespread IFR ceilings with
bases 300-1000 feet through most of the forecast area this morning.
RUC/WRF guidance pushing for similar timing to yesterday... with
gradually lifting ceilings through the morning and mix out between
17-19z for most locations. Early return of MVFR/IFR ceilings at 01-03z
for most locations. Onshore flow 10- 16kt with gusts up to 24 knots
through this afternoon with strongest winds near shore.
Vicinity of ksfo... IFR/MVFR through 18-19z. Breezy onshore winds
this afternoon. MVFR ceilings return 01-02z Friday.
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals... IFR/MVFR through 18-19z. Onshore
winds this afternoon. MVFR ceilings return 01-02z Friday.
Marine...as of 08:39 am PDT Thursday...high pressure along the
California coast will result in light to locally moderate
northwest winds. The strongest wind speeds will be through the
northern San Francisco Bay...off of the Sonoma coastline and along
the Big Sur coastline. Predominately gentle seas will persist
through the forecast period.
... Bay north of the Bay Bridge from 2 PM
Small Craft Advisory...Pigeon pt to pt pinos 0-10 nm from 2 PM
Small Craft Advisory...pt Arena to pt Reyes 0-10 nm from 2 PM
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm from 2 PM
Public forecast: Larry
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