Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service San Francisco Bay area
454 am PDT Sat Sep 5 2015

Synopsis...a region-wide warming trend is forecast to begin this
weekend and continue into much of next week as high pressure
builds over the state. Dry weather conditions will also continue
through next week.

&&

Discussion...as of 04:14 am PDT Saturday...a cooler and drier
air mass continues to filter into the region this morning in wake
of yesterday's passing short-wave disturbance. This feature also
helped to keep the marine layer from redeveloping much
overnight...with only patchy coastal stratus along the San Mateo
coast and around the southern portion of the Monterey Bay. These
clouds are forecast to burn-off shortly after sunrise with mostly
sunny conditions expected region-wide for the remainder of the
day. As the broad middle/upper level trough over the Pacific
northwest pushes further inland today...weak offshore flow will
develop off the surface and allow for warming temperatures this
afternoon. While temperatures will generally remain below seasonal
averages today...most locations will be a few degrees warmer
compared to Friday afternoon.

A more robust warming trend is then expected Sunday into Monday
as middle/upper level high pressure over the southwest portion of the
country builds westward...resulting in warming 850mb temperatures
and continued offshore flow in the lower levels. Surface
temperatures early next week will be around 5-7 degrees above
seasonal averages. The warming trend will then likely continue
into midweek as 850mb temperatures are forecast to approach or
exceed 20 degree c. This will push temperatures near the coast into
the middle/upper 70s to near 80 with inland areas warming into the
middle/upper 80s to middle/upper 90s in the warmest inland valleys. With
the broad middle/upper level ridge forecast to remain over the West
Coast for much of next week...dry weather conditions along with
above average temperatures will likely persist. In addition...low
clouds will likely remain absent for much of the forecast period
with dry boundary layer conditions as a result of the weak
offshore flow off the surface.

While this pattern will result in great weather conditions for
beachgoers this Labor Day weekend...a long period southerly swell
moving into the waters will result in hazardous conditions in the
surf zone. The primary concern will be from dangerous rip currents
and large shore break along the south and southwest-facing beaches
this weekend. Anyone visiting area beaches this weekend are urged
to use caution and remember to never turn your back to the ocean.

&&

Aviation...as of 4:42 am PDT Saturday...moderate to strong
northerly pressure gradients continue this morning...acv-sfo 4.8
mb...and uki-sts 2.4 mb. Lower humidity area-wide from the lower
to the upper levels is allowing for near optimum nocturnal cooling
and surface wind Delaware-coupling resulting in light/variable valley
winds. Northerly gradients forecast to persist as surface high
pressure builds over epac/northernmost California and briefly over to the
Great Basin tonight. Middle-upper level high will strengthen through
the period.

Vicinity of ksfo...VFR.

Ksfo bridge approach...VFR.

Monterey Bay area terminals...northwest winds forcing narrow band of low
clouds to persist over the southern Monterey Bay area. Kmry scattered-broken
until about 16z today otherwise should see sufficient vertical mixing
of drier air to provide clearing. VFR.

&&

Marine...as of 04:14 am PDT Saturday...high pressure over the
eastern Pacific and northernmost California will keep gusty
northwest winds going over the coastal waters through tonight. A
long period southerly swell will move into the coastal waters over
the weekend resulting in hazardous conditions alongshore.

&&

Mtr watches/warnings/advisories...
... Arena to pt Reyes 0-10 nm
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm
Small Craft Advisory...Pigeon pt to pt pinos 0-10 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm
Small Craft Advisory...pt Arena to Pigeon pt 10-60 nm
Small Craft Advisory...Pigeon pt to pt Piedras Blancas 10-60 nm

&&

$$

Public forecast: rgass
aviation/marine: canepa



Visit US at www.Weather.Gov/sanfrancisco

Follow US on facebook and twitter at:
www.Facebook.Com/nwsbayarea
www.Twitter.Com/nwsbayarea

National Weather Service Glossary of Abbreviations