Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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FXUS66 KMTR 111954
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1254 PM PDT Tue May 11 2021

.SYNOPSIS...Cooling conditions near the coast will gradually spread
inland through late week along with an increase in night/morning low
clouds. Near to slightly below normal daytime temperatures will then
persist into the upcoming weekend with mainly dry weather
conditions.

&&

.DISCUSSION...as of 12:50 PM PDT Tuesday...Slight cooling has
returned to the region in response to a deepening marine layer and
onshore flow near the coast. Meanwhile, light offshore flow
persists across the interior where temperatures are likely to max
out in the mid/upper 80s with a few spots reaching into the lower
90s. The onshore push is forecast to spread further inland through
this evening and more so into tonight, reducing fire weather
concerns in the North Bay and East Bay mountains/hills as well as
the interior East Bay Valleys. Given this and the fact that
offshore winds this afternoon have greatly diminished, the Red
Flag Warning previously in effect has been cancelled. However,
very dry conditions will persist through the remainder of the
afternoon across the interior.


The cooling trend will expand inland on Wednesday with low clouds
becoming more widespread near the coast and into the adjacent
valleys tonight into Wednesday morning. Meanwhile, temperatures
across the interior will remain well above average with high
pressure aloft. Look for temperatures to cool back to near seasonal
averages by late week as the mid/upper level ridge begins to flatten
and more zonal flow develops aloft.

Forecast ensembles then indicate a mid/upper level trough and
associated low will drop southward down the West Coast this upcoming
weekend. This feature will likely further deepen the marine layer
resulting in more widespread night/morning clouds along with cooler
daytime temperatures. While some of the deterministic models do
indicate the potential for light precipitation with this system
Friday night into Saturday, confidence is low at this time with
widespread beneficial rainfall unlikely.

&&

.AVIATION...As of 11:00 AM PDT Tuesday...For the 18z TAFs. VFR
continues across the Bay Area today. The afternoon will offer
breezy northwesterly winds that will weaken into the evening. Low
level clouds will return to the Monterey Bay this evening and the
SF Bay overnight. Confidence is low that the stratus will wrap
around to Oakland, so VFR conditions should continue around the SF
Bay through the night. However patchy fog may form in the late
night around KSTS. The Monterey Bay Terminals will begin to see
scattered clouds turn to broken and overcast overnight with
chances for fog lasting into the next morning.

Vicinity of KSFO...VFR through the evening. Northwesterly winds
will build into the afternoon peaking around 15 kts. Surface winds
will decrease in the evening and a few low level clouds will
filter into the area overnight but VFR will remain. Skies will
clear into the late morning.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR and mild winds will last through the
afternoon. Coastal stratus returns in the evening and ceilings
look to fall below 1000 AGL. Expect broken and overcast conditions
with fog overnight, leading to IFR and the possibility for LIFR
criteria to be met.

&&

.MARINE...as of 10:57 AM PDT Tuesday...Winds will continue to
diminish across the coastal waters today with locally breezy
conditions over the northern outer waters into this afternoon.
Light winds then expected mid-week before re- strengthening into
the weekend as the next system approaches. As winds diminish, seas
will also subside with a light northwest and southerly swell
prevailing.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm until 3 PM
             SCA...SF Bay until 9 PM

&&

$$

PUBLIC FORECAST: RGass
AVIATION: Murdock
MARINE: AS
FIRE WEATHER: RGass/Dykema

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