Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

FXUS66 KMTR 270435

Area Forecast Discussion
National Weather Service San Francisco Bay Area
835 PM PST Sun Feb 26 2017

.SYNOPSIS...A cold front with scattered showers over northernmost
California will move southeastward over the Bay Area and Central 
Coast very late tonight and Monday morning. Many locations will 
not see wet weather due to the more widely spaced weak convective
type of precipitation associated with this frontal system, but 
locations that do see wet weather will generally have light amounts
perhaps upwards of a tenth of an inch. Snow showers are likely 
over the higher elevations. Dry weather conditions then return for
the remainder of the work-week along with a gradual warming trend
as high pressure builds aloft.

&& of 8:35 PM PST Sunday...It was a picturesque day
in all locations with a chill in the air coupled with isolated to
widely scattered showers as northwesterly unstable flow continues.
The 0.39" precipitable water value on the most recent 00Z Oakland
sounding was only marginally higher compared to this morning's 
12z sounding; mainly dry air continues, freezing level near 4200 
feet and wet bulb zero near 3500 feet. One more reinforcing push 
of cold air visits Monday into Tuesday nudging 850 temperatures 
downward to -2C to -4C Monday into Tuesday. For comparison, 
inspection of all soundings per SPC's climatology page shows 
Oakland's late winter season 850 mb temperature has been colder 
(-6.8C on March 2nd). Nonetheless, unseasonably cold temperatures 
can be expected to close out the month. With March soon to be here
a fairly rapid return to upper level ridging will coincide with 
its start and extend the mainly dry stretch a bit further down the
road this week. Over the upcoming weekend the ridge will flatten 
out possibly allowing some light wet weather from the Pacific 
Northwest to reach as far south as the Bay Area.


.PREVIOUS of 12:50 PM PST Sunday...Aside from CU 
developing over the mountains/hills this afternoon, mostly sunny 
conditions prevail ahead of an approaching weather system to our 
north. The latest forecast models and current trends bring a 
frontal boundary across the region late this evening and through 
the overnight hours with isolated to scattered showers likely. 
These showers will likely impact the North Bay late this evening 
or tonight and shift southward through the Central Coast overnight
into Monday morning. Rainfall amounts in the range of a few 
hundredths of an inch to a couple tenths will be possible yet not 
all locations will pick up measurable precipitation. In addition, 
snow levels are forecast to lower again to the 3,000-3,500 foot 
range along the Central Coast with below 3,000 northward. Thus, 
should see some snow showers across the region with light 
accumulation in the higher elevations. Meanwhile, overnight 
temperatures will remain in the 30s to lower 40s as this system 
will bring a reinforcing shot of cooler air across the region.

Lingering showers will be possible into Monday morning before 
diminishing in coverage by the afternoon and evening. Dry weather 
conditions are then likely for the remainder of the week as high 
pressure builds out over the eastern Pacific. Temperatures will 
also begin a gradual warming trend late in the week with 
widespread 60s likely by Thursday and Friday. Overnight 
temperatures will also moderate some and only cool into the upper 
30s to lower 40s by late week, compared to the lower/mid 30s more 
common the next few nights. 

The upper level ridge is forecast to weaken a bit by the upcoming
weekend as a mid/upper level through approaches the Pacific 
Northwest. At this time, the best chance of precipitation will be 
north of the region yet cannot rule out the system clipping the 
far northern portion of the North Bay by Saturday night into 
Sunday. However, not expecting widespread heavy rainfall with most
locations remaining dry across the region through the extended 
forecast period. 


.AVIATION...As of 04:00 PM PST Sunday...Generally VFR through the
forecast period, aside from some overnight stratus development in
the North Bay valleys. That said, there is the possibility a 
passing shower could quickly lower ceilings down into the MVFR 
range. Primary area of shower activity looks to pass southward 
through the district in the late evening to overnight hours. There
could however still be a few lingering showers in the area on 

Vicinity of KSFO...Mostly VFR except possibly briefly down to 
MVFR during a shower. VCSH expected starting around 06Z. West 
winds 10 to 15 kt through early evening then diminishing. Moderate

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR. Light winds. Possible shower or two
late this evening through Monday morning. Moderate to high 

&& of 02:34 PM PST Sunday...A few showers can be
expected through Monday as a weak system moves through. No
significant swell trains are expected through the period with
winds forecast to stay under gale force levels.


     .Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm from 4 AM




Visit us at

National Weather Service Glossary of Abbreviations