Preview of NWS' New Version of Forecast
This preview is not operational and should not be used for support decisions.

Area Forecast Discussion (AFD)

Issued by San Francisco Bay Area, CA (MTR)

                            
000
FXUS66 KMTR 231547
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
847 AM PDT Tue Jul 23 2019

.SYNOPSIS...Inland temperatures will warm to above seasonal 
averages through the remainder of the week and into the upcoming 
weekend as high pressure dominates the weather pattern. The 
influence of a shallow marine layer and persistent onshore flow 
will keep conditions seasonably mild near the coast. 

&&

.DISCUSSION...as of 08:47 AM PDT Tuesday...Satellite imagery 
currently shows stratus over the waters and along the coast as the
marine layer remains at around 1000 ft AGL. Expect low clouds to 
dissipate over land by late morning leaving mostly clear skies 
across the region aside from some passing high clouds. A mid/upper
high continues to build over the Desert Southwest while an upper 
low sits just offshore of western Canada with an associated trough
extending southward along the west coast down to Northern 
California. The mid/upper high is circulating mid/upper level 
moisture across southern and eastern California that will generate
some high clouds over our area today. Mid/upper level instability
will also continue, but at least for today will be confined to 
our south and east. The aforementioned upper trough will act to 
stall this weeks warming trend for today. Some areas may even be a
few degrees cooler than yesterday afternoon. Highs this afternoon
along the coast will be mainly in the upper 60s to mid 70s with 
inland areas seeing widespread 80s and 90s. Isolated interior 
locations may reach triple digits. Warming will pick up again 
tomorrow and continue into the upcoming weekend while onshore flow
and a shallow marine layer keep coastal areas relatively mild.

&&

.PREV DISCUSSION...as of 02:51 AM PDT Tuesday...A shallow marine 
layer at about 800 feet in depth has resulted in low clouds over 
much of the Monterey Bay southward into the Salinas Valley. In 
addition, patchy stratus can be see on GOES-W satellite imagery 
along the San Francisco Peninsula as well as offshore. These 
clouds may fill in a bit through sunrise, yet will be less 
widespread compared to previous mornings. In addition, mid- level 
moisture rotating around the building mid/upper level high 
pressure over the Desert Southwest appears to have produced an 
isolated high-based shower over far eastern portion of San Benito 
County, now moving across western Fresno and Merced Counties. 
Overall, expecting only a few sprinkles from this if any 
precipitation is reaching the surface at all. Regardless, look for
mid/high level clouds to continue to move over the interior 
portion of the Central Coast through the morning. 

The aforementioned mid/upper level high pressure to our east will 
continue to be the dominate weather feature across the southwestern 
portion of the country through the remainder of the week. However, 
the ridge is forecast to be suppressed slightly over northern 
California today as an upper level trough just off of the British 
Columbia coast pushes into the Pacific Northwest. This will stall 
the warming trend a bit today with some inland locations potentially 
cooling by a few degrees. Regardless, look for widespread 80s and 
90s across the interior while upper 60s to middle 70s will be common 
near the coast. 

The warming trend will continue on Wednesday as the ridge 
strengthens over the region. Daytime temperatures will likely warm 
to around 10 degrees above seasonal averages over the interior. 
Meanwhile, a shallow marine layer and continued onshore flow will 
maintain cooler conditions near the coast with periods of 
night/morning low clouds and patchy fog. Temperatures cool slightly 
across inland areas Thursday and Friday, but will remain very warm. 
Look for an increase in mid/upper level clouds late in the week as 
monsoon moisture advects across the region around the ridge over the 
Desert Southwest. With this, will need to monitor for any potential 
of high-based showers and/or thunderstorms, mainly for Thursday 
night. 

Longer range guidance from both the ECMWF and GFS, as well as the 
ensembles, indicate the ridge of high pressure will shift westward 
and over southern California during the upcoming weekend. This will 
likely result in additional warming with daytime temperatures 
rebounding to above seasonal averages for much of the region. Thus, 
will need to monitor for increased heat risks across the interior by 
the weekend. 

&&

.AVIATION...as of 4:44 AM PDT Tuesday...The marine layer remains
compressed under large scale subsidence resulting in VLIFR-IFR on
the coastline and into the Salinas Valley. VFR is still reported 
at KMRY, but tempo IFR remains in the forecast for a few hours 
until 16z this morning. Inland it's VFR. Similar to yesterday the 
marine layer should scatter back to the coastline then return 
locally inland tonight and Wednesday morning.

Vicinity of KSFO...Conditions remain favorable for VFR to prevail
through the forecast period. Onshore wind increases by early
afternoon with gusts up to 20 knots possibly a few higher gusts 
up to 25 knots. 

SFO Bridge Approach...Similar to KSFO. 

Monterey Bay Terminals...VLIFR-IFR then clearing is anticipated 
around 17z this morning. VFR late morning into the afternoon then
VLIFR-IFR returning this evening.

&&

.MARINE...as of 2:51 AM PDT Tuesday...Breezy northwest winds will
persist today across the coastal waters. Winds will increase 
becoming gusty tonight and Wednesday as high pressure builds into 
the Pacific Northwest and northern California. Light southerly 
swell coupled with short period wind waves will continue through 
the week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tday...SCA...Pigeon Pt to Pt Pinos 0-10 nm from 9 AM
             SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
             SCA...Pt Reyes to Pigeon Pt 0-10 nm
             SCA...Mry Bay from 9 AM
             SCA...SF Bay from 3 PM

&&

$$

PUBLIC FORECAST: AS/RGass
AVIATION: Canepa
MARINE: Canepa

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