FXUS66 KMTR 061913
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
1213 PM PDT Tue Oct 6 2026
...New SHORT TERM, LONG TERM...
.KEY MESSAGES...
Updated at 1212 PM PDT Tue Oct 6 2026
- Hazardous heat inland persists through Thursday, never leave
children or pets in unattended vehicles!
- Elevated fire weather conditions persist in the interior
through Thursday
- Coastal flooding concerns due to astronomical tides and thermal
expansion through the weekend
- Hazardous beach conditions along Pacific coastline later this
week into the weekend due to long period swell
&&
.SHORT TERM...
Issued at 1212 PM PDT Tue Oct 6 2026
(This evening through Wednesday night)
Patches of fog and stratus linger at the immediate coast, associated
with a shallow marine layer that sits around 500 feet deep. The rest
of the region remains clear as large scale ridging results in
sinking air, thus suppressing cloud formation processes. The ridging
is also helping to compress the marine layer, so don't expect any
overnight stratus outside of the immediate coast and favored areas
adjacent to it, including the Petaluma Gap, the Golden Gate, and the
coastal plain around Monterey Bay. On the flip side, for higher
elevation areas above around 1000 feet, don't expect that much
relief at night. The marine layer inversion has set up right along
those areas, resulting in a thermal belting effect where overnight
lows remain in the upper 60s to middle 70s, limiting the ability of
the body to recover from the heat of the day. As a final note, as
the ridge has set up right over our area, local pressure gradients
are relatively low, and the onshore flow this afternoon has likewise
been neutered.
Over the last couple of days, the default model blend has been
running warmer than the observed temperatures across much of the
region. On a broad scale, this is relatively minor (around 3 degrees
warmer in the forecast across the inland valleys) so not a
significant deviation to correct for. At the immediate coast,
temperatures are significantly cooler than the model blend output
would otherwise suggest. For example, downtown San Francisco
reported a high of 71 yesterday compared to a forecast high of 80.
Based off that assessment, I have lowered the high temperatures for
today and Wednesday at the immediate coastal regions by around 5
degrees, into the middle 60s to lower 70s. This might still be an
overshoot in some patches of the coast where the stratus continues
to linger well into the afternoon. Elsewhere, high temperatures
remain in the 80s to the lower 90s near the Bays, while the interior
valleys should expect highs in the middle 90s to the triple digits
(near 105 in the warmest spots of interior Monterey County).
A Heat Advisory remains in effect for the interior regions through
the end of Thursday, excluding the coastal strip and the northern
Salinas Valley, as widespread Moderate HeatRisk blankets the
interior, corresponding to a moderate risk of heat-related illnesses
for sensitive populations, including children, the elderly, pregnant
women, people with chronic illnesses, and people who work or live
outdoors without access to adequate cooling or hydration. In
addition, many of the higher elevations are seeing Major HeatRisk,
corresponding to a high risk for heat-related illnesses for anyone
without hydration or cooling. Follow these tips to avoid heat
exhaustion and heatstroke:
* Stay hydrated and drink plenty of fluids.
* Wear lightweight, light-colored clothing.
* Reduce time spent outdoors or stay in the shade.
* Never leave people or pets unattended in vehicles.
* Use sunscreen if going to the coast or the pool.
Minor coastal flooding is expected at the Bayshore locations along
the San Pablo Bay through the next few days as up to 0.9 ft of
thermal expansion surge significantly impacts the tidal level. At
the San Francisco tidal gauge, high tide is expected to be 0.6 ft
above normal (6.48 ft MLLW) at 8:58 PM Tuesday 10/6 and 0.6 ft above
normal (6.44 ft MLLW) at 10:19 AM Wednesday 10/7. Confidence in
these specific values is moderate and the high tide yesterday
evening ran to 0.8 ft above normal (6.64 ft MLLW) representing a
surge of around 1.0 feet.
&&
.LONG TERM...
Issued at 1212 PM PDT Tue Oct 6 2026
(Thursday through next Monday)
Hot and dry conditions continue through Thursday with the Heat
Advisory for the inland locations expiring at 10 PM that night. The
first hints of a pattern change arrive on Friday, when an upper
level trough forming over British Columbia and the Pacific
Northwest, a decaying husk of an upper level low coming in from the
Central Pacific, and a weakening Hurricane Rachel (expected to be a
Tropical Storm by Friday) will interact to flatten the upper level
ridge and bring troughing across the West Coast for the upcoming
weekend. As a side note, with the breakdown of the ridge on Friday,
confidence in the High temperatures will drop closer to, or
slightly below, the seasonal averages by the weekend, with highs in
the 70s across the inland valleys and the 60s at the Pacific coast
and near the Bays. Ensemble model cluster analysis is coming around
to some sort of trough across the region for the weekend, and
continues to hold on to chances for something resembling an inside
slider pattern towards the end of the weekend into the early part of
next week, although confidence is not high. As the trough deepens,
various clusters show the trough axis developing somewhere from
central Oregon and Northern California to the Great Basin. Many of
the scenarios support some form of northerly flow over the Bay Area
and Central Coast, but the exact orientation of the low will
determine whether the flow retains a more westerly component or
pushes more from due north or the northeast.
Minor coastal flooding continues along the bayshore San Pablo Bay on
Thursday with high tide at San Francisco expected to be 0.8 ft above
normal (6.68 ft MLLW) at 10:51 AM Thursday 10/8. With higher
astronomical tides expected Friday into the weekend, a Coastal Flood
Advisory may need to be issued for bayshore locations along the San
Francisco and Monterey Bays closer to that time. In addition,
southerly swell from Rachel will increase the risk of rip currents
and sneaker waves later this week into the weekend as long period
swell of 15 to 18 seconds arrives.
&&
.AVIATION...
(18Z TAFS)
Issued at 1042 AM PDT Tue Oct 6 2026
After some LIFR conditions early this morning impacting Monterey
Bay Region and HAF, conditions have improved. Expecting mostly
VFR today all terminals with IFR/LIFR for HAF due to lingering
marine layer. High pressure remains overhead compressing the
marine layer again tonight. Shallow moist layer will inch inland
leading to higher conf for IFR to LIFR for Monterey Bay Region and
HAF. Airport mins are poss for MRY/SNS. Conf was less than 15-20%
for other terminals therefore didn't include any low clouds/fog.
Vicinity of SFO...VFR through the period. NE flow into the
afternoon less than 10 kts then onshore for afternoon/evening
rush. Likely see a NE push again Wednesday AM.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals... VFR through this evening, but as noted
above expect shallow CIGs/FG to return. Higher conf on impacts to
SNS, but conf high enough to mention for MRY as well.
&&
.MARINE...
(Today through Sunday)
Issued at 939 AM PDT Tue Oct 6 2026
High pressure off the Pacific Northwest Coast and low pressure
near Southern California will maintain gentle to moderate
northerly breezes through Thursday. Northerly breezes will then
increase strong to very strong Friday into Saturday, bringing
widespread hazardous conditions for small craft. Frequent gale
force gusts are likely across the northern waters during this
time. Moderate seas will prevail through Thursday, building to
become rough to very rough Friday into Saturday.
&&
.FIRE WEATHER...
Issued at 456 AM PDT Tue Oct 6 2026
Maximum and minimum temperatures 10 to 20 degrees above normal
across the interior with a compressed marine layer at the coast
will persist through Thursday. Widespread poor minimum relative
humidity is expected across the interior with little-to-no
recovery for the higher terrain. Active thermal belting and prolonged
burn periods will continue across the higher terrain. Winds
remain the limiting factor, with diurnal winds prevailing except
for light northerly/offshore flow overnight across the higher
terrain. ERC values are forecast to reach near records during the
next seven days from the hot and dry conditions. An inside slider
like pattern succeeding this heat event will likely keep elevated
fire weather conditions around.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 10 PM PDT Thursday for CAZ503-504-506-508-
510-512>518.
Coastal Flood Advisory until 1 PM PDT Thursday for CAZ506.
PZ...None.
&&
$$
SHORT TERM...DialH
LONG TERM....DialH
AVIATION...MM
MARINE...MM
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Prepared by Boulder-Creek.com Weather at: Tue Oct 6 16:30:02 PDT 2026
From the National Weather Service
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