FXUS66 KMTR 072345
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
445 PM PDT Mon Sep 7 2026
...New AVIATION, MARINE...
.KEY MESSAGES...
Updated at 1214 PM PDT Mon Sep 7 2026
- Hazardous conditions at Pacific Coast beaches through Monday
evening
- Warming and drying trend will bring widespread moderate to
major HeatRisk through Thursday
&&
.SHORT TERM...
Issued at 1214 PM PDT Mon Sep 7 2026
(This evening through Tuesday night)
Hazardous conditions at Pacific Coast beaches continues today. Long
period southerly swell from distant Tropical Storm Marie will result
in an increased risk for sneaker waves and strong rip currents with
breaking waves up to 10 feet. Stay off the beach and remain out of
the water to mitigate your risk. Minor coastal flooding will be
possible during high tide this evening for bayshore locations along
the San Pablo Bay in Marin County. The warming and drying trend has
already commenced with conditions notably warmer and drier than they
were 24 hours ago. High pressure will build in from the east
tomorrow, peaking Wednesday and Thursday. Uncertainty in the
forecast stems from Marie's moisture. Fortunately from a fire
weather standpoint, the mid-level moisture and associated
rain/thunderstorm chances are expected to remain confined to our
south and west. However, associated high-level clouds are expected
to stream in Tuesday into Wednesday which could make highs lower and
lows higher due to decreased solar insolation and radiational
cooling, respectively. We aren't even going to have the marine layer
to save us this heat event. Reason being, flow aloft has an easterly
component as it wraps into Marie. If we miraculously get any sort of
marine layer, expect it to be compressed below 500 feet which would
bring dense fog to coastal locations. A Heat Advisory has been
issued for all areas and will run from 10AM Wednesday through 10PM
Thursday. Temperatures will be 10 to 20 degrees above normal with
minimal onshore flow. There are high probabilities for moderate and
even major HeatRisk during this time; in fact, San Francisco has a
high probability (70%+) that the eastern half of the city will reach
or exceed a maximum temperature of 80 degrees on Wednesday. Onshore
flow is expected to return on Thursday which may be enough to remove
coastal locations from the Heat Advisory; however, we will likely
wait to see how Wednesday's forecast fares before making any
changes. To put this heat event into context, 850 mb temperatures
and 500 mb heights are going to be between the 90th percentile and
daily record values which indicates that we are dealing with an
anomalously warm airmass with higher than normal heights. Two things
that are preventing this from being a widespread record breaking
event is September is climatologically the warmest month of the year
for most of our area and we have benchmark records dating back to
1944.
&&
.LONG TERM...
Issued at 1214 PM PDT Mon Sep 7 2026
(Wednesday through next Sunday)
Global ensemble clusters are in agreement that the ridge will be
tamped down by an upper-level low digging into the Pacific Northwest
Friday. This will kickoff the cooling trend with temperatures
moderating to near normal. The tightening of the pressure gradient
will bring an increase in onshore flow and strong northerly breezes
across the waters.
&&
.AVIATION...
(00Z TAFS)
Issued at 442 PM PDT Mon Sep 7 2026
Northwesterly winds have developed this afternoon and are likely
to persist through sunset before diminishing. Wind become
light/variable overnight before becoming offshore at times early
Tuesday morning. Low confidence for stratus to return early
Tuesday morning around the Bay Area with the greatest potential
being around the Monterey Bay terminals. VFR conditions are
forecast regionwide beyond 16Z-18Z Tuesday. Onshore winds return
Tuesday by early afternoon, yet may be delayed in timing and not
occur until closer to 00Z Wednesday.
Vicinity of SFO...VFR. Onshore winds have developed this
afternoon and are forecast to persist through late evening. Winds
ease into Tuesday morning and become light/variable or offshore at
times. There is low confidence for stratus to return early
Tuesday morning with generally less than 20% probability of
reaching MVFR ceilings. Thus, have left out of the official
forecast at this time. Onshore winds return late Tuesday morning
and will persist through the evening.
SFO Bridge Approach...The potential for MVFR CIGs Tuesday
morning is less than 10%. Otherwise, similar to SFO.
Monterey Bay Terminals...VFR. Onshore winds have developed this
afternoon between 06-12kt. Winds ease late this evening after
sunset and become light/variable early Tuesday morning. There is
now a 30- 60% probability for IFR between approximately 06Z-17Z.
Thus, have introduced IFR conditions into the official forecast
overnight and into early Tuesday morning. Once any low clouds that
do develop mixout, expecting VFR conditions to return by around
17Z.
&&
.MARINE...
(Tonight through next Saturday)
Issued at 442 PM PDT Mon Sep 7 2026
Northwest winds gradually diminish to gentle to moderate tonight
which then prevails through the remainder of the week. Winds look
to increase late this week into the weekend. A long period
southerly swell induced by distant tropical cyclone activity in
the East Pacific prevails into next week.
&&
.BEACHES...
Issued at 1213 AM PDT Mon Sep 7 2026
A Beach Hazards Statement is in effect through 11 PM this evening.
Moderate to long period swell will increase the chance for
sneaker waves, since there are 2 different sets of southerly
swell, and their energy will periodically combine. In addition to
sneaker waves, expect strong rip currents and breaking waves up to
10 ft. As this is a holiday weekend and the weather is otherwise
pretty nice, the exposure to the risk is high. Avoid the water if
you're not an expert swimmer. If caught in a rip current, swim
parallel to shore until you stop feeling the pull. Even on the
beach, be prepared for sneaker waves this weekend and never turn
your back on the ocean.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement until 11 PM PDT this evening for CAZ006-
505-509-529-530.
Heat Advisory from 10 AM Wednesday to 10 PM PDT Thursday for
CAZ006-502>506-508>510-512>518-528>530.
PZ...None.
&&
$$
SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...RGass
MARINE...RGass
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Prepared by Boulder-Creek.com Weather at: Mon Sep 7 20:30:03 PDT 2026
From the National Weather Service
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