Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
834 am PDT Friday Jul 31 2015
Synopsis...a cooling trend can be expected today and through the
weekend. Subtropical moisture streaming into our area may produce
a few isolated showers and thunderstorms today and tonight.
Discussion...as of 8:35 am PDT Friday...line of showers that had
been across a portion of Monterey and San Benito counties has
greatly diminished over the past 30 minutes. In fact...last couple
of images from the kmux radar shows virtually no shower activity
left since the band has moved into Santa Cruz and Santa Clara
counties. The trigger for the showers appears to be a weak
vortmax/shortwave currently moving northward through our County Warning Area.
Latest models in continue to downplay the threat of convection
through our area however in light of the small band that developed
this morning will keep a mention of showers and thunderstorms
today for all locations. Will make adjustments to the probability of precipitation for the
afternoon shift if nothing fires by then.
Overall forecast package looks to be on track.
Previous discussion...kmux radar has been showing echoes moving
from southeast to northwest across Monterey and San Benito
counties for the past several hours. Salinas Airport was reporting
light rain during last hour's observation...and there is evidence
of a trace of rain falling within the last hour here at the
weather office in Monterey. A few other observations on mesowest
have reported a couple hundredths of an inch...Laguna
Seca...Pebble Beach to name a few. These showers will continue to
move to the northwest out over the ocean this morning. Additional
convection is expected to develop by this afternoon mainly across
the higher terrain. Shower chances are expected to wane by
Saturday morning as the flow becomes more westerly.
Onshore flow will continue during the weekend which will bring
cooler temperatures to even inland areas. By early next week...an
upper level low over the Gulf of Alaska will deepen and its
associated trough will extend along the West Coast. This will keep
cooler temperatures across the district as well as breezy north winds
over the coastal waters and near-shore areas.
Aviation...as of 5:00 am PDT Friday... for 12z tafs...scattered
high level clouds will continue to traverse the region today.
A chance of showers and isolated thunderstorms is possible across
the district. Patchy low clouds will scatter out around 17z-18z
today. Light and locally variable winds will increase this
afternoon to 15 to 25 knots.
Vicinity of ksfo... IFR to MVFR ceilings will scatter out around 17z-
18z today. Light winds will increase to around 15 to 20 knots
expected this afternoon.
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...IFR ceilings will scatter our around
18z today. Light and variable winds will increase to around 10 to
15 knots this afternoon.
Beaches...as of 04:16 am PDT Thursday...a marginally energetic
southerly swell continues along the coast this morning.
However...unlike yesterday the swell heights are down and the
period is now 15 seconds. No beach hazard statement will be
issued...but a few beach may see some locally hazardous
conditions. Use caution if you head to the beach
today...especially south facing ones.
Marine...as of 08:26 am PDT Friday...isolated thunderstorms will
move across the coastal waters today. These storms will move in
from the southeast and traverse the region toward the northwest.
Erratic winds and moderate showers may possibly accompany these
storms. Otherwise...light west to northwest winds will continue
across much of the region through the weekend. The strongest winds
will be located in the northern San Francisco Bay each
afternoon...especially near Angel Island.
... Bay from noon
Public forecast: Bell/Sims
Visit US at www.Weather.Gov/sanfrancisco
Follow US on facebook and twitter at: