National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS66 KMTR 102049
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
149 PM PDT Mon Aug 10 2020

.SYNOPSIS...A slight cooling trend is forecast to occur today and
Tuesday, especially across the interior. Meanwhile, little change
is anticipated near the coast with the typical ebb and flow of
low clouds each night/morning. Warming is likely late in the week
and into next weekend.

&&

.DISCUSSION...as of 01:48 PM PDT Monday...Morning low clouds have
rolled back to the immediate coast, but persistent southerly flow
over the coastal waters has kept low clouds locked in along the
coastline. Given the south flow a few favored spots are seeing sun
along the coast like Monterey and locally north of Pt Sur. On the
larger scale the N-S gradient has weakened and the E-W gradient
has increased and is over 2 mb now. Therefore, despite inland
sunshine temperatures this afternoon are running a few degrees
cooler than Sunday. High temperatures today will top out in the
60/70s at the coast and 80/lower 90s interior.

An upper level trough over the PacNW will deepen and sag southward
toward CA through midweek. The lowering 500mb heights will keep
night and morning low clouds in place the next few days.
Additionally, the overall airmass will cool keeping temperatures
seasonably cool.

If you`re hoping to see the Perseid meteor shower you`ll have a
few things working against you. Night and morning low clouds and
some moonlight. Best chance for seeing meteors the next few nights
will be fair interior locations or in the hills.

After Wednesday the high pressure system currently sitting over
the Desert Southwest will build westward. This upper level high
is on track to peak over the weekend. There were some bigger
differences between the ECMWF and GFS regarding the strength of
the high, but the GFS is now catching up. Both the GFS and ECMWF
now show 850mb temps in the mid-upper 20C range. Those warm 850mb
temps will translate to high temperatures in the 90s to lower 100s
across the interior. As temperatures increase so will the heat
risk. Latest guidance puts heat risk in the moderate to high
category across interior Monterey/San Benito.

The position of the high pressure system will help to advect some
tropical moisture northward from west of Baja. Lots of
uncertainty with details, but it does appear some upper level
moisture arrives Thursday afternoon and more on Friday.
Thankfully, no major instability being forecast at this time and
will mostly likely be high level clouds. Nonetheless will have to
watch closely to see if the threat for convection changes.




&&

.AVIATION....as of 10:30 AM PDT Monday...for 18Z TAFs. VRF
conditions have returned to the terminals as of 1730Z in response
to dissipating stratus. Look for VFR conditions to prevail through
the afternoon with a typical increase in onshore winds. Low clouds
likely to return inland slightly earlier this evening for
terminals closer to the coast while surface wind speeds also
diminish. A deeper marine layer will also likely bring lowering
ceilings to inland terminals by early Tuesday morning.

Vicinity of KSFO...VFR. W/NW winds will increase to around 12-15
KT around 20Z and persist through the early evening before
diminishing slightly. MVFR/IFR ceilings likely to develop beyond
10Z Tuesday and persist through about 18Z Tuesday.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR. An increase in NW winds to 9-12 KT
is likely later this morning and will continue through the
afternoon with low clouds lingering near the coast. An early
return of stratus and diminishing winds is likely around 03Z with
IFR to LIFR ceilings persisting through Tuesday morning.

&&

.MARINE...as of 10:30 AM PDT Monday...A weak upper level low
pressure system just west of San Francisco and surface high
pressure to the north of this feature will bring light southerly
winds through Tuesday. Winds will switch to the west to northwest
Tuesday night through Friday but will remain generally light.
Mixed seas will continue through the period with a short period
northwest swell and a longer period southerly swell. Southerly
swell will increase Tuesday and Wednesday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...SCA...SF Bay until 9 PM

&&

$$

PUBLIC FORECAST: MM
AVIATION: RGass
MARINE: RGass

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/nwsbayarea
www.twitter.com/nwsbayarea
www.youtube.com/nwsbayarea