FXUS66 KMTR 071917
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
1217 PM PDT Mon Sep 7 2026
...New SHORT TERM, LONG TERM...
.KEY MESSAGES...
Updated at 1214 PM PDT Mon Sep 7 2026
- Hazardous conditions at Pacific Coast beaches Monday
- 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...
(18Z TAFS)
Issued at 1054 AM PDT Mon Sep 7 2026
Weak offshore aloft has resulted in VFR conditions across much of
the region. Onshore winds are forecast to increase this afternoon
and into the early evening before diminishing after sunset and more
so into Tuesday morning. Winds today are forecast to be weaker than
previous days however. Low confidence for stratus to return early
Tuesday morning with the greatest potential being around the
Monterey Bay terminals. Onshore winds return Tuesday by early
afternoon, yet may be delayed in timing.
Vicinity of SFO...VFR. Light offshore flow persists at SFO this
morning, but is forecast to become west-northwesterly between 21Z-
23Z and prevail until late this 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 a 10-30% probability of reaching MVFR CIGs. Thus, have
left out of the official forecast at this time.
SFO Bridge Approach...The potential for MVFR CIGs Tuesday
morning is less than 10%. Otherwise, similar to SFO.
Monterey Bay Terminals...VFR. Currently variable winds at both
sites with increasing onshore winds between 19Z-20Z. Winds ease
late this evening after sunset and become light/variable early
Tuesday morning. There is a 20-40% probability for sub-VFR between
approximately 08Z-17Z, however confidence is not great enough to
include in the official forecast at this time. Once any low clouds
that do develop mixout, expecting VFR conditions to return by
around 17Z.
&&
.MARINE...
(Today through Saturday)
Issued at 1054 AM PDT Mon Sep 7 2026
Moderate to fresh northwest breezes gradually diminish across the
coastal waters today becoming more moderate. 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 Labor Day. 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 14:30:03 PDT 2026
From the National Weather Service
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