FXUS66 KMTR 151128
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
428 AM PDT Wed Jul 15 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 101 PM PDT Tue Jul 14 2026

 - Moderate HeatRisk continues across the interior Wednesday

 - Breezy onshore winds through Thursday 

 - Elevated fire weather conditions through Thursday

&&

.SHORT TERM...
Issued at 1139 PM PDT Tue Jul 14 2026
(Tonight through Thursday)

It was hot Tuesday. San Francisco hit 76, Santa Rosa 97, Livermore 
102, and San Jose 95. I made the mistake of baking bread in the 
afternoon and my house in Monterey got to 81 degrees. The highs were 
about 5 degrees warmer than forecast, driven by strong high pressure 
to the east and totally clear skies. The 03Z WPC Surface Analysis 
shows a mesoscale 1019 mb high over northern Nevada that was 
stronger than expected. The 6-member PGE WRF ensemble (POMMS EPS) 
predicted the SFO-WMC gradient would be between +3 and +4 mb at 
04Z, and it was actually observed at -3.8 mb. In other words the 
weather models missed this mesoscale high pressure over Nevada. 
This helped keep the air dry today and discouraged the marine 
layer from reforming. Temperatures are going to remain relatively 
warm overnight, but not quite as warm as last night thanks to the 
clear skies and enhanced radiational cooling. Similar high 
temperatures are expected Wednesday afternoon with slightly 
stronger winds in the afternoon as a trough starts to approach the
coast. The overnight temperatures will cool much more effectively
Wednesday night.

With the hot temperatures, low humidity, and moderate onshore winds, 
fire weather conditions will be elevated Wednesday and Thursday. A 
few stations are currently reporting red flag conditions across the 
North and East Bay. This will continue over the next couple days. 
Wednesday is hot and dry with moderate winds. Thursday will be a 
little cooler, but the winds will be a bit stronger. The elevated 
fire weather will continue through the nights as well. The lack of 
marine layer and strong thermal belting will keep higher elevations 
warm with poor humidity recoveries. 

&&

.LONG TERM...
Issued at 1139 PM PDT Tue Jul 14 2026
(Thursday night through next Tuesday)

A cooling trend starts Thursday as a low pressure trough
approaches the coast. There has been a slight change from 
yesterday however. It now looks like the Rocky Mountain 500 mb 
high will remain strong enough to force the incoming low north 
into the Pacific Northwest. The associated trough will still 
bring us cooler temperatures, but maybe not as drastic or quick as
we thought yesterday. Temperatures will be about 5 degrees above 
normal Thursday, near normal Friday, and 5 degrees cooler than 
normal over the weekend and into early next week. The marine layer
will also start to reform during this cooling trend, with low 
clouds likely to return to the typical gloomy areas by Friday 
morning.

The large scale mid level flow will stay out of the SW between the 
fairly stationary Eastern Pacific trough and central US ridge. This 
keeps the conveyer belt open for surges of tropical moisture, 
particularly if a recurving tropical cyclone drags some of the deep 
tropical moisture into the subtropics. We now have a tropical 
cyclone in the NE Pacific near 15N, 110W named TROPICAL DEPRESSION 
FIVE-E. This system is expected to become a hurricane by Thursday 
and continue NW through the weekend. Depending on the track and the 
ultimate strength of this tropical cyclone, it has the potential to 
bring moisture far enough north to be sucked into the conveyer belt 
and delivered to the Bay Area. The uncertainty is pretty high 
with tropical cyclone tracks, but it looks likely that there will 
be some moisture arriving Sunday or Monday from this system. The 
amount of moisture is still up in the air. The ECMWF ensemble mean
has dropped from 1.0" yesterday to 0.8" today (90th percentile to
75th percentile), but the spread between members remains quite 
large. Why do we care about this? Elevated moisture surges bring 
the potential for high based thunderstorms and dry lightning that 
can spark wildfires.

&&

.AVIATION...
(12Z TAFS)
Issued at 424 AM PDT Wed Jul 15 2026

Currently VFR at all terminals. High confidence in VFR through the 
afternoon with low to moderate confidence on IFR ceilings returning 
to the coastal terminals of HAF, MRY, and SNS tonight. Diurnal winds 
will prevail.

Vicinity of SFO...Currently VFR with westerly flow. High confidence 
in VFR and diurnal winds prevailing through the TAF period. 45% 
chance for wind gusts to reach 35 knots, primarily between 23Z and 
03Z.

SFO Bridge Approach...Low probability (20% chance) of low clouds 
below FL045 developing across the San Mateo Bridge Approach tonight.

Monterey Bay Terminals...Currently VFR and calm at MRY and VFR with 
northwesterly flow at SNS. Moderate confidence on IFR ceilings 
returning to the terminals tonight with a greater chance at MRY than 
SNS.

&&

.MARINE...
(Today through Monday)
Issued at 424 AM PDT Wed Jul 15 2026

Widespread hazardous conditions for small craft are expected into
Friday across the inner and outer waters due to fresh to strong
northwesterly breezes. Gale force gusts are expected along the
coastal jet regions of Point Reyes and Point Sur. The afternoon
sea breeze will create hazardous conditions for small craft within
the bays. Moderate seas will prevail with intermittent rough seas
in the outer waters through Friday.

&&

.FIRE WEATHER...
Issued at 101 PM PDT Tue Jul 14 2026

The warm temperatures we have had the past several days and 
continued warm weather has resulted in fuels rapidly drying this 
week. ERC charts are expected to exceed the 97th percentile across
the Mid Coast to Mendocino zone and get close to the 97th 
percentile across the Central Coast. Fire weather concerns will 
remain elevated this afternoon through Thursday due to near 
critically dry conditions, gusty onshore winds, and very dry fuel 
conditions. This may result in additional fire starts particularly
across the interior and higher elevations. Unsettled weather is 
possible next weekend with returning potential for dry 
thunderstorms and gusty, erratic winds.

RGass/Flynn

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory until 4 AM PDT Thursday for CAZ006-506-
     508.

     Heat Advisory from 10 AM this morning to 10 PM PDT this evening 
     for CAZ516-517.

PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this 
     evening for Mry Bay-SF Bay N of Bay Bridge.

     Small Craft Advisory from 9 AM to 3 PM PDT Thursday for Mry Bay.

     Small Craft Advisory until 3 PM PDT Thursday for Pt Arena to Pt 
     Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.

     Small Craft Advisory from 9 AM this morning to 3 PM PDT Thursday 
     for Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-
     60 NM-Pt Reyes to Pigeon Pt 0-10 nm.

     Small Craft Advisory until 9 AM PDT Thursday for Pt Pinos to Pt 
     Piedras Blancas 0-10 nm.

     Gale Warning from 9 AM to 3 PM PDT Thursday for Pt Pinos to Pt 
     Piedras Blancas 0-10 nm.

&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...Sarment
MARINE...Sarment

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Prepared by Boulder-Creek.com Weather at: Wed Jul 15 04:30:03 PDT 2026