FXUS66 KMTR 072014
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
114 PM PDT Wed Oct 7 2026

...New SHORT TERM, LONG TERM...

.KEY MESSAGES...
Updated at 1259 PM PDT Wed Oct 7 2026

 - Hot inland temperatures continue through Thursday

 - Sharp cool-down this weekend

 - Coastal flooding and large swell this weekend

 - Light rain possible early next week

&&

.SHORT TERM...
Issued at 1259 PM PDT Wed Oct 7 2026
(This evening through Thursday night)

Another hot day. Inland temperatures have already climbed into 
the 90s, and the hottest spots will get close to 100 degrees later
this afternoon. At 500 mb a ridge is extending over the Bay Area,
originating from high pressure over the Channel Islands. The 850 
mb temperature is 21.5C, which is well above the 90th percentile,
and near the daily max for this time of year. Winds are generally
onshore, which is bringing good relief to the coast, where 
temperatures are in the 60s and 70s. As we've seen the last few 
days, there is a chance for coastal fog in the morning within a 
shallow marine layer.

The ridge will remain in place Thursday, although it will start to 
weaken through the day as a cut-off low pressure system approaches 
from the west. This will allow the marine layer to expand a bit. 
Nevertheless inland temperatures will be broadly similar Thursday, 
and the Heat Advisory remains in effect through the day. 

&&

.LONG TERM...
Issued at 1259 PM PDT Wed Oct 7 2026
(Friday through next Tuesday)

The long term forecast is quite active. I'll start with a 
synoptic breakdown and then list the individual hazards in greater 
detail. By Friday the ridge will break down as the cut-off low off 
the coast starts to dominate the pattern. This feature will merge 
with the jet stream to the north and the remnants of Hurricane 
Rachel to the south to form a high amplitude trough over California 
through the weekend.

Temperatures: The pattern change will lead to a drastic drop in 
temperatures. High temperatures Wed-Thu are 10-20 degrees above 
normal for this time of year, and will drop to 5-10 degrees below 
normal by Saturday. Friday is the transition with some relief before 
the big cool down arrives Saturday. Livermore, for example, has 
been dealing with 100+ degree high temperatures since last 
Saturday, and we have 72 degrees in the forecast for this 
Saturday. That's the good news.

Wind: The incoming trough will bring much lower surface pressure to 
California, with a central pressure likely below 1000 mb somewhere 
in the Central Valley this weekend. By Saturday, the gradient 
between this low pressure and higher pressure over the Pacific will 
generate strong to near gale force northwesterly winds across the
coastal waters and along Pacific beaches. These winds will push 
inland through gaps and passes as fresh to strong west - southwest
winds Saturday afternoon. We're probably not quite at wind 
advisory level, but bring a wind breaker if you're going to Fleet 
Week or anywhere near the beach. 

Coastal Flooding: With warm waters driven by El Nino, we are seeing 
some remarkable tidal anomalies. Every tidal station in the Bay Area 
down to Monterey is recording a full foot of residual surge (extra 
water above the tide table prediction). With clear skies, light 
winds and high pressure, this is caused primarily by thermal 
expansion from the warm water. The current sea surface temperatures 
are in the low to mid 60s, which is around 5-7 degrees above 
normal for this time of year. Beyond the local SST, the regional 
waters are quite warm across the Eastern Pacific, especially at 
depth. There has been a lot of talk about the 3+ C SST anomaly 
from El Nino (a record), but the larger anomaly is found at depth,
closer to the thermocline. In the Nino 3.4 region, the water 
temperature at 100 m depth is over 10-13.5C above normal. That's 
18-24F. Warmer water takes up more volume through thermal 
expansion, and the only place that extra water can go is up. A 
Kelvin wave of even warmer water has reached southern California, 
where the SSTs are in the 70s and the tidal anomaly is roughly 
1.2-1.4 feet above normal. That's heading our way, moving at about
5-10 mph up the coast. All of this extra water will make the 
typically innocuous Spring tide driven by a normal new moon feel 
more like a King Tide this weekend. The incoming winds and swell 
will push the tide even higher. We are expecting high tides this 
weekend to be somewhere from 1.2 to 1.5 feet above normal. That's
enough to trigger minor coastal flooding across low-lying areas 
in the San Francisco Bay and southern Monterey Bay. This is just a
sign of things to come this season. The extra foot of water will 
be here for several months, including during the real king tides 
in Nov, Dec, and Jan.

High Surf: In addition to the high tides, there will be large waves 
this weekend. This is due to a combination of long period southerly 
swell from Hurricane Rachel and large wind waves from the near gale 
force conditions over the coastal waters. The forerunners from 
Rachel will arrive as early as late Thursday and will build in 
height through the weekend. A new set of westerly swell arrives 
Sunday from a hurricane force extratropical storm in the central
north Pacific. As the swell reaches the beaches, breaking waves 
of 15 feet are possible. Particularly during high tide, these 
wave will run much further up the beach and cause erosion. There 
will also be stronger currents than normal due to both the large 
swell and big tidal swings. Expect a Beach Hazards Statement or 
High Surf Advisory to be issued in the next day or two.

Rain: While the moisture from the remnants of Rachel will initially 
be confined to the southern California, there is a potential for 
some wrap around moisture to bring light rain early next week. 
Roughly half of the European ensemble show measurable precip at 
SFO Monday-Tuesday, with the ensemble mean around 0.05". None of 
the current simulations show anything very impactful.

The cooler weather looks like it will stick around next week, as
the wind and waves calm down.

&&

.AVIATION...
(18Z TAFS)
Issued at 1004 AM PDT Wed Oct 7 2026

Patchy fog and LIFR stratus lingers at the immediate coast with the 
rest of the region remaining VFR through the daytime. A gentle to 
moderate onshore pattern wind develops in the afternoon and 
evening hours. Overnight stratus development is limited to the 
immediate coastal region, with a low confidence for radiational 
fog development at STS. Some clearing will occur late Thursday 
morning close to the end of the TAF period. 

Vicinity of SFO... High confidence for VFR conditions through the 
TAF period. Moderate west-northwest winds will develop in the 
afternoon and evening hours, with light winds overnight into the 
morning.

SFO Bridge Approach... Similar to SFO

Monterey Bay Terminals... VFR conditions through the rest of the 
daytime with a gentle to moderate northwest winds in the afternoon 
and evening hours. LIFR stratus will develop in the evening hours 
with moderate confidence for fog development, lower confidence in 
the clearing tome on Thursday morning. 

&&

.MARINE...
(Today through Monday)
Issued at 1004 AM PDT Wed Oct 7 2026

Gentle to moderate north breezes and moderate seas prevail
through Thursday. Strong to near gale force north winds will
develop across the northern outer waters Friday, spreading across
the rest of the waters this weekend. Rough to very rough seas will
build Friday into the weekend as a result. Long period southerly
swell arrives Friday with long period westerly swell arriving
Sunday.

&&

.FIRE WEATHER...
Issued at 410 AM PDT Wed Oct 7 2026

Hot and dry conditions will lead to elevated fire weather conditions 
across the higher terrain through Thursday. Temperatures 10 to 20 
degrees above normal and poor minimum relative humidity will 
continue away from the compressed marine layer at the coast. The 
higher terrain will experience active thermal belting, little-to-no 
recovery with nocturnal drying across the highest peaks, and thus 
prolonged burn periods. Winds remain the limiting factor, with 
diurnal winds prevailing except for light northerly/offshore flow 
overnight across the higher terrain. ERC values will rise to near 
records during the hot and dry conditions. A pattern change Friday 
into the weekend will bring cooler, moister, and windier 
conditions.

Sarment

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory from 9 AM Friday to 3 PM PDT Tuesday for 
     CAZ006-508-529-530.

     Heat Advisory until 10 PM PDT Thursday for CAZ503-504-506-508-
     510-512>518.

     Coastal Flood Advisory until 4 PM PDT Wednesday for CAZ506.

PZ...None.
&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...DialH
MARINE...DialH

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Prepared by Boulder-Creek.com Weather at: Wed Oct 7 16:30:02 PDT 2026