Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
908 PM PDT sun Apr 26 2015
Synopsis...high pressure will build through Monday keeping
temperatures warm under sunny skies. A dry cold front will approach
the coast by Tuesday allowing winds to turn back onshore with a
modest cooling trend. Dry and seasonable weather is then forecast
Wednesday through next weekend.
Discussion...as of 9:02 PM PDT Sunday...it's a fairly quiet
evening weather-wise after a day with warmer temperatures across
the area. 8 PM temperatures continue to settle back with readings
now in the middle to upper 50s immediate coast and nearest the Bay to
the 60s inland.
The sub-tropical ridge will continue to amplify over northern
California through Monday evening then shift eastward to Nevada
late Monday night into Tuesday. Above normal day-time warmth will
persist on Monday...but by Tuesday west-northwest winds will strengthen
helping to start a cooling trend that'll likely carry through
late week. The majority of cooling will be first located at the
immediate coast and near the Bay waters then gradually spread into
the inland valleys through the remainder of the week. The cooling
will be relative however since above to well above normal daily
highs will gradually settle back...through middle-late week...to near
normal highs for late April and early may. A weak open wave 500 mb
height trough will migrate from the higher latitude westerlies
over the epac and become nearly stationary over norcal through the
end of week. A separate colder trough located farther upstream
south of the Aleutians will get propelled eastward by the jet
stream and reach the Pacific northwest and norcal by either Monday or
Tuesday of next week.
Previous discussion...as of 2:32 PM PDT Sunday...its a sunny and pleasant
Sunday afternoon across the Bay area with temperatures running
6-12 degrees warmer than Saturday as high pressure builds over the
region. Northerly gradient is building with 4.5 mb down the coast
and now 1 mb offshore from the Great Basin. This should keep skies
mostly clear overnight with perhaps some coastal clouds along the
San Mateo and Monterey coastline by morning. Otherwise the
synoptic pattern will favor north winds in the hills...turning
offshore or northeast by morning. This will set the stage for a
sunny and warm Monday across the district with the warmest inland
spots approaching the upper 80s to around 90 degrees. Expect
widespread 70s and lower 80s around the Bay with comfortable 60s
at the coast.
As early as Monday night winds will turn back onshore as a dry
cold front approaches the northern California coast. Expect
stratus to return to the coast by Tuesday morning as this feature
moves through northern California. Noted cooling trend will then
occur on Tuesday...especially near the coast but even inland with
an early and strong seabreeze as the upper trough moves over
Oregon by Tuesday afternoon.
Behind that feature the upper pattern will trend zonal with
perhaps a baggy upper trough by the end of the week. The end
result on the surface weather will be minimal with dry and
seasonable weather forecast from midweek through next weekend.
Were getting deep into The Shoulder seasons now when storms are
rare but the Summer marine layer hasn't necessarily become
In the long range the 240 hour European model (ecmwf) and GFS both depict an upper
low approaching the region with the 10-16 day GFS runs keeping the
pattern cyclonic with near to below normal temperatures. No big ridges or
warm spells in sight...just seasonable as we head into may.
Aviation...as of 4:41 PM PDT Sunday...a strong northerly gradient
is expected to maintain mainly clear skies across the region
through the forecast period. Moderate westerly winds will ease
overnight becoming locally offshore in the early morning hours.
Otherwise light west winds will prevail through Monday morning.
Vicinity of ksfo...VFR conditions expected through the forecast
period. Sustained west winds around 15 to 22 knots with gusts to
around 30 knots expected through this evening. Winds will ease
overnight. High confidence.
Sfo bridge approach...similar to ksfo.
Monterey Bay area terminals...VFR conditions expected through the
forecast period. Sustained west winds around 10 to 15 knots with
gusts to around 20 knots expected through this evening. Winds will
ease overnight. High confidence.
Marine...as of 8:57 PM PDT Sunday...high pressure will maintain
moderate northwesterly winds across the coastal waters the overnight
hours. Winds are anticipated to further strengthen midweek as a
cold front pushes towards the California coast.
... Pt to pt pinos 0-10 nm until 2 am
Small Craft Advisory...pt Arena to pt Reyes 10-60 nm
Small Craft Advisory...pt Reyes to Pigeon pt 10-60 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm
Small Craft Advisory...Pigeon pt to pt pinos 10-60 nm
Small Craft Advisory...pt Arena to pt Reyes 0-10 nm until 5 am
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm until 5 am
Small Craft Advisory...pt pinos to pt Piedras Blancas 10-60 nm
Public forecast: canepa/rww
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