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Area Forecast Discussion (AFD)

Issued by San Francisco Bay Area, CA (MTR)

FXUS66 KMTR 171017

Area Forecast Discussion
National Weather Service San Francisco Bay Area
317 AM PDT Wed Apr 17 2019

.SYNOPSIS...A warming trend is forecast through Thursday. 
Temperatures are expected to climb well above normal by Thursday, 
with widespread 80s for inland locations and 70s near the coast. A
cooling trend is then forecast to begin on Friday and continue 
into the weekend. Dry conditions are forecast through the weekend 
and well into next week.


.DISCUSSION...As of 3:15 AM PDT Wednesday...A few patches of low 
clouds developed near the ocean overnight, but most areas remain
clear early this morning. Fort Ord profiler data indicate a 
marine inversion has not yet developed, so expect coastal low 
clouds to remain patchy through the morning hours. 

A warming trend will get underway today as an upper ridge centered
just offshore begins to build eastward over California. Inland
temperatures today are forecast to be as much as ten degrees 
warmer than yesterday. Persistent light onshore flow will keep 
coastal temperatures from warming more than a few degrees. 

The upper ridge will strengthen over California into Thursday, 
continuing the warming trend across our region. A shallow marine 
layer will likely form near the coast by tonight. However, the 
latest local WRF shows drier air in the boundary layer making its
way to the coast by Thursday morning as light offshore flow 
develops. Thus, warming on Thursday will occur in all areas, 
including areas near the ocean. Inland areas are forecast to see 
widespread highs in the 80s on Thursday, while coastal areas warm 
into the 70s. While Thursday's temperatures are forecast to be 10 
to 15 degrees warmer than normal, record highs are not 

Thursday is expected to be the warmest day of the week. Onshore 
flow will return by Friday as the upper ridge shifts to our east 
and weakens. Cooling on Friday will be greatest in coastal areas 
where marine layer clouds will likely be on the increase. Inland 
areas will experience more modest cooling on Friday. Cooling will
continue into Saturday, especially inland, as an upper trough 
develops over northern California. Shower activity associated with
this trough is forecast to mostly remain to the north and 
northeast of our area, and model consensus is for dry weather to 
persist across our area through the weekend. It should be noted, 
however, that the latest NAM brings light precip as far south as 
the northern fringes of Sonoma County by Saturday morning. 

Temperatures will begin to rebound on Sunday, with more robust
warming then anticipated next Monday and Tuesday as an upper ridge
builds over California once again.  

&& of 10:45 PM PDT Tuesday...VFR conditions prevail 
at all terminals, but current fog product satellite imagery shows
areas of stratus starting to form along the coast south of the 
Golden Gate. Key forecast question remains ceiling development 
during overnight and early morning hours. Mixed signals from 
models and statistical guidance. Upshot though is that it appears 
likely for the Monterey Bay terminals and unlikely for those in 
the San Francisco Bay Region.

Vicinity of KSFO...Onshore winds will continue to diminish
overnight becoming light and variable during the morning 
hours. Latest model output indicates diminished chances of late 
night/early morning ceiling development so am maintaining VFR 
conditions throughout the forecast period, but confidence is on 
the low side.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...MVFR ceilings projected to develop over
the next few hours and then continue well into the morning before
clearing. Light winds turning onshore 10 to 15 kt Wednesday
afternoon. Moderate confidence.


.MARINE...As of 2:57 AM PDT Wednesday...High pressure centered 
west of Monterey Bay will keep northerly winds over the coastal 
waters. Winds will be locally stronger along the coast north of 
Point Reyes and south of Point Sur this afternoon. A longer period
moderate northwest swell will decrease through out today and 


     .Tday...SCA...Pt Arena to Pt Reyes 0-10 nm




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