National Weather Service Raw Text Product

Displaying AFOS PIL: AFDMTR Received: 2017-09-14 04:07 UTC

FXUS66 KMTR 140407

Area Forecast Discussion
National Weather Service San Francisco Bay Area
907 PM PDT Wed Sep 13 2017

.SYNOPSIS...Shower and thunderstorm chances have ended across the
entire region this evening. Expect dry weather through the 
weekend. Temperatures are forecast to warm slightly on Friday and 
Saturday, but then cool beginning Sunday. Much cooler weather, and
locally blustery conditions, are likely early next week as a deep
upper trough develops over the Pacific Northwest and northern 
California. There is also a slight chance of showers in the North 
Bay beginning Monday.


.DISCUSSION...As of 9:05 PM PDT Wednesday...The upper low that
produced scattered showers and thunderstorms across our region
over the past few days is currently moving inland near Point
Conception and is forecast to move quickly east into southern
California overnight. All shower activity ended across our region
by sunset and expect no further convective precipitation. A
forecast update was recently completed to remove all thunderstorm
chances from the forecast this evening. This update also included
adjustments to cloud cover for the next few days. Considerable 
low level moisture remains across our region and patchy drizzle 
could possibly develop out of this low level moisture late 
tonight and into early Thursday as a shortwave trough approaches 
from the northwest. 

As the shortwave trough swings through later on Thursday, we will
see a drier northwest flow develop which should help most areas 
clear in the afternoon. Clearing may be slower in southern coastal
areas, especially around the southern periphery of Monterey Bay. 
Temperatures on Thursday will remain relatively cool. Breezy 
conditions are expected with brisk west to northwest winds, 
especially in the afternoon and evening hours.

Slightly warmer weather is forecast for Friday and Saturday while
our area is under dry northwest flow aloft. Coastal areas will see
temperatures return to about normal, while inland areas will
likely remain a bit cooler than average for this time of year.

By late in the weekend an unseasonably deep upper trough is
forecast to drop south out of the Gulf of Alaska and by Monday 
settle in over the Pacific Northwest and northern California. 
This will result in cooling beginning on Sunday and then much 
cooler weather by Monday and Tuesday. We will also see blustery 
conditions...especially near the coast...with locally strong and 
gusty northwest winds possible by Monday afternoon and evening. 
This trough may also generate scattered shower activity on Monday 
and Tuesday, with best chances in the North Bay.

Both the GFS and ECMWF move the upper trough very slowly to the
east next week, and so temperatures will likely remain cooler than
average through the end of the week, with only modest warming
expected late in the week. 


.AVIATION...As of 5:00 PM PDT Wednesday...Upper low over the central
California coast has kept stratus in over the North Bay and the 
northern SFO Bay Area and MRY Bay Area today. The upper low will
slowly move east tonight but onshore flow behind the system will
bring stratus back over all terminals. Southwest winds at SFO will
keep low cigs out until after the airport evening rush.  

Vicinity of KSFO...MVFR after 06Z possibly later. Southwest winds
to 10-12 kt through 03Z. 

SFO Bridge Approach...same as KSFO.

Monterey Bay Terminals...A brief scattering out of clouds through
03Z then becoming MVFR.

&& of 5:00 PM PDT Wednesday...Shower and thunderstorm 
chances will significantly decrease through the evening as an 
upper level low shifts onshore. Northwest winds will increase 
through the next 24 hours, starting over the northern coastal 
waters, eventually affecting the southern coastal waters by late 
Thursday morning.


     .Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pt Arena to Pt Reyes 0-10 nm from 9 PM
             SCA...Pt Reyes to Pigeon Pt 0-10 nm from 3 AM
             SCA...SF Bay




Visit us at

Follow us on Facebook, Twitter, and YouTube at: