Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
238 PM PDT Monday Oct 20 2014
Synopsis...dry weather conditions will develop tonight through
Wednesday in wake of today's frontal passage. Temperatures will
then slowly warm through late week as high pressure builds south
of the region. Another Pacific system will bring rain chances to
the North Bay late in the week and then across the entire region
Discussion...as of 02:35 PM PDT Monday...a weak frontal boundary
continues to push inland this afternoon with light precipitation
falling over the region. Rainfall amounts today have been light
with most inland areas receiving only trace amounts or no
rainfall at all. Meanwhile...areas of the North Bay reported
rainfall totals between one-tenth to one-quarter of an inch. A
slight chance of precipitation will continue over the North Bay
through this evening as the main middle/upper level trough pushes
into the Pacific northwest.
In wake of this system...dry conditions will develop region-wide
tomorrow through Wednesday. Generally expecting zonal flow aloft
through middle/late week as high pressure builds south of the
region. This will cause temperatures to warm slight...especially
across the central coast. Further north...a deeper moisture Plum
continues to be forecast by the models over Oregon and northern
California. This may get a push southward and bring rain chances
back to the North Bay as early as Thursday as an upper low
deepens over the Gulf of Alaska. By late week...the models are in
better agreement in showing a middle/upper level trough developing
off the Pacific northwest coast. This would likely push another
frontal boundary through the forecast area Friday night into
Saturday...bringing another shot of rainfall to a larger portion
of the region. This too would cool temperatures for the upcoming
weekend back to below seasonal averages.
Toward the end of the upcoming weekend...conditions dry out as
the upper level trough and associated support push inland and
northwest flow sets up aloft. The models generally develop zonal
flow over the region again early next week...yet differ on
potential for precipitation. Will continue to monitor the latest
forecast model output in the coming days to see if they become
better aligned. Stay tuned!
Aviation...as of 10:30 am PDT Monday...a narrow cold front is
currently moving northwest to southeast through the sf Bay area.
Ceilings and visible will be MVFR to IFR at times as the rain moves
through. Behind the front ceilings will quickly improve. Winds are
light southerly ahead of the front...briefly gusty from the west
with the front...before becoming light westerly. Low clouds will
be limited tonight though fog is likely at sts.
Vicinity of ksfo...MVFR with light rain through around 19z. Then
improving to VFR through evening. Moderate confidence. Westerly
winds the rest of the day...increasing to around 15 knots this
afternoon. Stratus possible early morning tomorrow.
Ksfo bridge approach...similar as ksfo.
Monterey Bay area terminals...ceilings becoming MVFR with light rain
possible early the afternoon as the front moves across the
terminals. Clouds clearing middle to late afternoon behind the front.
Winds turning west with frontal passage.
Marine...as of 02:35 PM PDT Monday...a weak frontal system
continues to move through the southern waters. Light southerly
winds ahead of the front will turn northwest this afternoon and
increase overnight...particularly south of Point Sur. Large
northwest swell is starting to move into the coastal waters and
will persist through Tuesday.
... Bar advisory for sf bar
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm
Public forecast: rgass
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