Small Craft Advisory 160, NWS San Francisco Bay Area, CA

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1052 PM PDT Tue Jul 25 2017

.SYNOPSIS...A gradual warming trend will get underway beginning on
Wednesday and continue through late week. By Thursday and into the
weekend, afternoon temperatures will warm to above seasonal averages
for inland areas while coastal locations remain cooler. Above average
temperatures are then likely to persist into early next week.

&&

.DISCUSSION...as of 9:12 PM PDT Tuesday...A vertically extensive,
nearly stationary, and dry low pressure area is located near the
Bay Area this evening. This low is dry except it is responsible
for helping to produce ongoing scattered thunderstorms over the
highest terrain of northern and eastern California.

It was a nice late July day, and temperatures have settled back
and remain comfortable over most if not all locations this evening
with 9 pm temperatures in the upper 50s along the immediate coast
and 60s near the bays and inland valleys. A deep marine layer will
persist tonight into Wednesday with clouds and fog coverage similar
to last night's and early this morning's coverage. The aforementioned
low pressure area will gradually dissipate and move eastward through
mid-week. A mid-upper level high pressure will redevelop and cause
a warming trend into this weekend and next week.

&&

.PREV DISCUSSION...as of 01:38 PM PDT Tuesday...Temperatures across
the region this afternoon are generally running near to a few
degrees above those 24 hours ago. In addition, low clouds have
mixed out well given the deep marine layer in place with mostly
sunny conditions for most coastal and just about all inland areas.
With the marine layer forecast to remain between 2000-2500 feet
in depth overnight, look for low clouds to return to the coast
late this evening and then spread inland through the overnight.

The mid/upper level trough and associated low pressure system that
has brought a few days of cooler than average temperatures to the
region will begin to lift northward on Wednesday. This will allow
for the air mass aloft to warm as the upper level high over the
southern portion of the country builds back toward the West Coast.
Thus, look for a warming trend to begin by Wednesday afternoon with
temperatures up by about 3 to 6 degrees for inland areas. Meanwhile,
coastal areas will continue to stay around seasonal averages due to
continued onshore flow and marine influences.

Additional warming is expected from late in the week into early next
week as the mid/upper level ridge of high pressure builds over the
southwestern portion of the country. There remains model differences
in the placement of the ridge as well as how strong it will become.
Thus, it is difficult at this time to nail down exactly which day
will be the warmest. However, do expect inland temperatures to warm
to above seasonal averages with 90s more widespread in the higher
elevations and in the valleys/interior. By late week, will also see
temperatures in the warmest inland areas warming into the 100-105
degree mark. At this time, not expecting widespread heat impacts,
yet will need to monitor given the current level of uncertainty in
the models. With the ridge building aloft, also expect the marine
layer to become more compressed with less inland penetration of
overnight/morning low clouds. Also worth noting, conditions near the
coast are not forecast to warm all that much given the persistent
onshore flow and typical influences from the Pacific.

&&

.AVIATION...as of 10:52 PM PDT Tuesday...For 06z TAFs...Low
clouds are filling in along the coast and through coastal gaps and
valleys. Southerly flow persists along the coast. Downsloping
will keep cigs out of select terminals till later tonight. Low
clouds will scatter out around 17z Wednesday morning.

Moderate confidence.

Vicinity of KSFO...VFR conditions will prevail through late
tonight with MVFR/IFR cigs returning around 11z-12z Wednesday
morning. Cigs will scatter out around 17z Wednesday morning.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...MVFR/IFR cigs will prevail through
tonight then scatter out around 17z-18z Wednesday morning.

&&

.MARINE...as of 9:00 PM PDT Tuesday...A weak area of low pressure
off the California coast will continue to produce a southerly
flow today along the immediate coast. West to northwest winds will
return tomorrow as high pressure builds over the Eastern Pacific.
Several tropical disturbances in the Pacific will bring a long
period southerly swell to the coastal waters at the end of the
week and through weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...None.

PUBLIC FORECAST: Canepa/RGass
AVIATION/MARINE: CW

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