Scientific Forecaster Discussion
fxus66 kmtr 261302
Area forecast discussion
National Weather Service San Francisco Bay area
502 am PST sun Feb 26 2017
Synopsis...dry weather is forecast for most of today. Shower
chances will develop by late afternoon as a weather system
approaches from the northwest. This weather system will continue
to produce shower chances through Monday evening. Rainfall
accumulation will be light. Dry weather conditions are forecast
from Tuesday through the remainder of the week as high pressure
builds over the region. Along with the dry weather, expect a
warming trend during the second half of the week.
Discussion...as of 2:40 am PST Sunday...a weak weather system is
moving into south-central California early this morning. This
system dropped light rain across portions of Monterey and San
Benito counties overnight. Up to two-tenths of an inch of rain
fell in the Santa Lucia mountains and along the Big Sur coast.
But for the most part rainfall was limited to just a few
hundredths. Radar shows rainfall is dissipating across the far
southern end of our forecast area at the present time, which is
consistent with model forecasts. Rainfall is expected to end in
all areas by daybreak.
The next system can be seen on infrared satellite imagery dropping
south along the coast of the Pacific northwest. This system is
forecast to track to the southeast and into northern California by
this evening. As the system approaches later today, scattered
shower activity may begin in the North Bay by late afternoon.
Also, the NAM shows isolated showers developing over the hills
south and east of Monterey Bay late in the day in areas where
residual moisture from the departing system remains. Otherwise,
expect dry and cool conditions today under partly cloudy skies.
Scattered showers are forecast to continue tonight and through
Monday as an upper trough gradually deepens across eastern
California and into the Great Basin. This system will not have a
lot of moisture to work with and so rainfall totals are expected
to be light...generally less than a quarter of an inch through
late Monday. Shower activity is expected to taper off on Monday
evening and end by late Monday night as the trough moves off to
the east. A cold airmass will arrive with this system and snow
levels will decrease to 2500-3000 feet by Monday. But since
precipitation amounts are expected to be light, only a dusting of
snow is possible on most Bay area peaks. Some of the higher
mountains in Monterey County may see as much as an inch or two of
snow where heavier showers develop.
Skies are expected to clear late Monday night and temperatures
will drop down close to freezing in the coldest valleys by
daybreak Tuesday, especially in the North Bay valleys.
Dry weather is forecast from Tuesday on through the end of the
week as an upper level ridge builds over California. Monday night
will probably be the coolest night of the week, with nighttime
temperatures expected to moderate as the week progresses. Daytime
highs will gradually warm through the end of the week.
The upper ridge is forecast to weaken slightly next weekend as a
storm system moves into the Pacific northwest. That system may
clip the far northern end of our forecast area with rain by late
next weekend, otherwise dry weather should prevail through next
weekend, along with mild temperatures.
Aviation...as of 03:34 am PST Sunday...for 12z tafs. Currently
VFR across all sites. Patchy valley fog possible early this
morning. VFR cigs and vis expected throughout forecast period,
with the exception of sts. Possibility of showers late tonight
Vicinity of ksfo...VFR. Generally light winds this morning
increasing to 10-15 kt west to northwesterly flow by this
Sfo bridge approach...similar to sfo.
Monterey Bay terminals...VFR. Light winds.
Beaches...a beach hazard statement was issued for the threat of
sneaker waves on Sunday. A long period swell arriving Sunday
morning, along with fair weather and light morning winds, will
bring a moderate risk of sneaker waves to North Bay and Bay area
coastal beaches. Arrival of the long period swell will coincide
with a rapidly rising tide on Sunday morning, pushing more energy
up the beach. West and northwest facing and steep sloped beaches
will be at greatest risk. The threat is expected to abate in the
afternoon as the tide drops, onshore winds develop, and long
period waves transition to shorter periods. Bfg
Marine...as of 2:02 am PST Sunday...low pressure is exiting the
coastal waters to the south. Another system will enter the area
Sunday night bringing moderate to fresh northerly conditions.
Monday Onward conditions should remain moderate to fresh with
possible near gale conditions later this week. No significant
swell trains are expected through the period.
Public forecast: dykema
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