FXUS66 KMTR 030901
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
201 AM PDT Sun May 3 2026
...New SHORT TERM, LONG TERM...
.KEY MESSAGES...
Updated at 1201 PM PDT Sat May 2 2026
- Cooler temperatures through the early part of this week with a
chance for drizzle and light rain, mainly along the coast
- Widespread stratus persists overnight and into the morning
through Sunday
- Warmer and drier conditions return for the middle of the week
&&
.SHORT TERM...
Issued at 201 AM PDT Sun May 3 2026
(Today and tonight)
Onshore winds continue to carry clouds and cooler air farther
inland. 24 hour trends show cooler to much cooler air is reaching
the higher elevations of the forecast area as well. Temperatures
vary from the 50s to the 40s at 1 am. A cloudy, chilly start and
continuation of cool air advection will slow the diurnal warming
process today. There may be spotty light drizzle. Forecast highs
are in the 60s today though it may be difficult to break out of
the 50s along the immediate coastline. The best chance of the sun
breaking through the clouds will be farthest inland from late
morning through afternoon. Onshore winds, low clouds and chilly
temperatures prevail tonight. A few additional patches of light
drizzle are possible.
&&
.LONG TERM...
Issued at 201 AM PDT Sun May 3 2026
(Monday through Saturday)
Residual polar jet stream winds on the back side of the 500 mb
closed low currently to our west will have already merged with
subtropical jet stream winds by Monday. By Monday the center of
the 500 mb low is forecast to be located over the Central Coast
to the Sierra Nevada/westernmost NV. The forecast gets a little
more challenging later Monday and early Tuesday with respect to
wet weather potential over our forecast area. Our current official
forecast carries light rain (0.10" or less) developing over the
North Bay and the East Bay and dry elsewhere during this time.
However, something to keep in mind is recent output e.g. from the
ECMWF/GFS/NAM show greater measurable rain later Monday and early
Tuesday. Lingering cold air aloft, with the 500 mb low cold core,
including possibly temporarily surface cooled air i.e. higher
surface pressures locked over the highly varied terrain of CA
while the mechanism for rainfall in this case becomes warm air
advection at ~ 850 mb to 700 mb (up to ~ 10K feet up) arrives
from the north and interacts with the colder air. At this time
per model forecasts it's forecast as stratiform precipitation vs
convective/unstable. Precipitable water is still forecast to peak
0.90" to 1" during this time. If the wetter pattern does develop,
it'd bring more widespread beneficial light to moderate rain across
more of our forecast area. Stay tuned to further updates.
From mid to late week high pressure aloft moves in from the west
and northwest. Compressional warming within the high will steepen
850 mb temperatures well above normal and likewise with the help
of the May sun angle, surface temperatures will warm well above
normal for early May. A quick check on forecast 850 mb temps on
the ECMWF show readings nearing the 90th percentile on Oakland
upper air sounding climatology for the time of year. Daytime
surface high temperatures far from any cooler maritime influences
will climb to the 80s to lower 90s by late in the week.
&&
.AVIATION...
(06Z TAFS)
Issued at 934 PM PDT Sat May 2 2026
High clouds are now obscuring low clouds around the region.
However, enough terminals and webcams continue to advertise MVFR
CIGs. Current taf package will keep MVFR CIGs well into Sunday
afternoon. Late Sunday afternoon and Sunday night confidence
decrease as the marine layer becomes less pronounced and begins to
mix. That being said, hard to bet against stratus already there
and HREF does show some clouds reforming. Breezy onshore flow
will return again Sunday afternoon.
Vicinity of SFO...MVFR CIGs through the Sunday AM rush. VFR and
gusts 20-25kt Sunday afternoon. MVFR CIGs return Sunday night.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...MVFR CIGs for much of Sunday. Small
window late Sunday afternoon where some SCT could occur.
&&
.MARINE...
(Tonight through next Friday)
Issued at 934 PM PDT Sat May 2 2026
High pressure to the north will maintain moderate to fresh
northerly breezes through early Sunday morning. Seas will also
subside on Sunday as winds continue to diminish. Moderate seas and
a gentle to moderate NW breeze prevail Sunday into the early work
week. Winds will gradually increase throughout the remainder of
the work week.
&&
.BEACHES...
Issued at 1201 PM PDT Sat May 2 2026
Long period northwest swell, with periods of 15 seconds or above, is
expected to arrive along the Pacific coast today. These long period
swells increase the risk of sneaker waves and rip currents,
particularly as the period between swell impulses results in lulls
of around 20 to 30 minutes before larger sets of waves arrive. Due
to the dangers, a Beach Hazards Statement for all Pacific coast
beaches comes into effect at 11 AM today and remains in effect until
11 PM Sunday night. Never turn your back to the ocean! Don't be
fooled by calmer seas; observe the waves for at least 20 minutes
before approaching the coast.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through this evening for CAZ006-505-509-
529-530.
PZ...None.
&&
$$
SHORT TERM...Canepa
LONG TERM....Canepa
AVIATION...MM
MARINE...MM
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Prepared by Boulder-Creek.com Weather at: Sun May 3 04:30:03 PDT 2026
From the National Weather Service
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