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Area Forecast Discussion (AFD)

Issued by San Francisco Bay Area, CA (MTR)

FXUS66 KMTR 181737

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1037 AM PDT Wed Jul 18 2018

.SYNOPSIS...Seasonably warm and dry weather will continue across 
the interior with marine air keeping conditions cooler near the 
coast. Monsoon moisture will move into California which may bring
a slight chance of high-based thunderstorms on Thursday. Otherwise,
look for an increase in high level clouds and continued warm 
temperatures through late week.


.DISCUSSION...as of 08:54 AM PDT Wednesday...Very little change 
in weather conditions compared to 24 hours ago with most locations
reporting temperatures withing a few degrees of those yesterday 
morning. In addition, low cloud cover is also similar to that on 
Tuesday even with a bit more compressed marine layer now between 
1,000-1,200 feet in depth. This should help for the cloud cover to
burn-off a bit more quickly through the remainder of the morning 
and give way to mostly sunny conditions in the afternoon. Thus, 
look for slightly warmer temperatures this afternoon region-wide, 
but only by a few degrees or so. Will also focus our attention
back to the potential for high-based convection Thursday into
Friday across the region. While chances are not high, the
potential is there and worth looking into. With that said, the 
ongoing forecast for today remains on track and no major updates 
are anticipated at this time. 


.PREV DISCUSSION...as of 3:16 AM PDT Wednesday...The marine layer has 
compressed slightly and is now around 1000 feet per the Fort Ord 
profiler. Coastal stratus has pushed inland once again filling the
valleys. Patchy fog is also being reported near the coast. Look 
for another warm day today across inland locations with highs 
expected to top out in the 90s to around 100 in the very warmest 
areas. Near-coastal sites will be in the 60s to mid 70s. Today 
should be the warmest day with temperatures cooling a few degrees 
by Thursday.

As the upper ridge edges eastward later in the week, increased
low and mid-level moisture will enhance the afternoon thunderstorm
possibility across mainly the eastern and southern portions of
California through the end of the week. Latest model guidance now
keeps shower chances confined to areas outside of our CWA so pops
were lowered for the Thursday time frame, although confidence
remains low. There will likely be some afternoon cloud buildups, 
especially over higher terrain of San Benito and eastern Monterey 

The upper ridge will then shift farther east over the weekend with
a baggy trough forecast along the coast. Little overall change in
temperatures expected through the remainder of the forecast
period, with night and morning coastal stratus/fog. 


.AVIATION...As of 10:29 AM PDT Wednesday...For 18Z 
TAFS...Earlier burn off this morning with terminals VFR. Tonight
do expect some cigs to roll back in, but coverage will likely be
less than this morning. Will also see an increase in mid/high
level clouds as monsoon moisture streams in from the SE. 

Overall conf is medium to high.

Vicinity of KSFO...VFR this afternoon. Similar to yesterday winds
will ramp up this afternoon with gusts over 20kt possible. Lower
conf on cigs tonight impacting SFO. Some models actually show a
hole around SFO with cigs on the edges. Will keep cigs in for now,
but may be removed in later updates. 

SFO Bridge Approach...Similar to SFO this afternoon. Better chance
for cigs to impact approach later tonight.

Monterey Bay Terminals...VFR this afternoon. Cigs will return this
evening with patchy fog possible late tonight.


.MARINE...as of 08:54 AM PDT Wednesday...Light to moderate winds
will persist for much of the coastal waters as high pressure
remains anchored off the Pacific  Northwest Coast. Winds will be
locally stronger north of Point Reyes. Gusty seabreezes will
develop north of the Bay Bridge to  the Delta this afternoon and
evening and likely again Thursday  afternoon and evening.
Southwesterly swell is forecast to mix with northwesterly swell
this weekend.


     .Tday...SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...SF Bay from 1 PM




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