FXUS66 KMTR 032009
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
109 PM PDT Mon Aug 3 2026
...New SHORT TERM, LONG TERM, MARINE...
.KEY MESSAGES...
Updated at 1155 PM PDT Sun Aug 2 2026
- Moderate HeatRisk in the interior through Tuesday, becoming
patchy midweek
- Near critical fire weather threat across the interior North and East
Bays, and the Diablo and Santa Lucia ranges through Monday
with elevated fire weather threat through the week
- Widespread Moderate HeatRisk looks to return for the end of the
work week.
&&
.SHORT TERM...
Issued at 1255 PM PDT Mon Aug 3 2026
(This evening through Tuesday night)
Nearterm:The southerly surge continues to inch its way northward
along the coast and finally made it past Pt Reyes. The surge has
really taken a bit out of temperatures along the immediate coast
this afternoon. 24 hr trends show many locations along the
coastline are running cooler than Sunday, which isn't surprising
with nearby clouds. On the flip side, head inland and away from
the surge influence and temps are soaring into the 90s and lower
100s. As such, Heat Adv remains in effect through this evening for
Interior North Mts and Interior East/South Bays.
Tonight through Tuesday night:
The surge will become less of a surge and more just onshore with
more stratus. Moderate marine layer stratus coverage for inland
areas tonight. This stratus will bring some relief and better RH,
but above the shall layer will remain mild and dry.
Interesting set up for Tuesday as the upper level pattern shows a
slight rebound of the ridge, but lower surface levels keep the
southerly/onshore flow. Pretty hard to bet again stratus and
cooler SST along the coast. As such, temperatures for Tuesday will
be within a few degrees of Monday, but on the cooler side. Just
enough to knock down HeatRisk values to Moderate with little to no
Major.
Tuesday night will see even more stratus coverage with a slight
deepening.
One final concern for the short term will be smoke/haze. Ample
fire activity across OR/WA will push some smoke over the coastal
waters. Longer range RRFS actually brings some smoke/haze to the
coastal waters late Tuesday into Wednesday.
&&
.LONG TERM...
Issued at 1255 PM PDT Mon Aug 3 2026
(Wednesday through next Sunday)
Rinse and repeat for the long term, but in the other direction
with a gradual warming and drying trend.
Upper level high pressure that briefly flattened will rebuild
over the West Coast beginning late Wednesday lasting through at
least Friday. While there is a slight reprieve in temps mid-week
inland heat and increasing HeatRisk return Thursday and more so
Friday. In fact, some of the guidance suggest an airmass
approaching 30C at 850mb. 30C is a pretty toasty airmass, which
would easily yield max temps over 100 across the interior. Would
also expect mild overnight lows in the hills. If this trend
continues we may need another Heat Advisory.
&&
.AVIATION...
(18Z TAFS)
Issued at 1133 AM PDT Mon Aug 3 2026
Current satellite imagery shows stratus receding to the coastline.
Widespread VFR conditions prevail through the day as onshore winds
increase to around 10-15 kt before easing into the evening. We had a
bit of a disorganized southerly surge of marine stratus that not
only brought IFR-LIFR ceilings to the coastline, but also south to
southwesterly winds. We can anticipate another southerly surge to
happen again tonight, though there is low to medium confidence on
the exact arrival of marine stratus and how far inland it will
perturb. Highest confidence for IFR ceilings, intermittently LIFR,
at HAF and the Monterey Bay terminals. High confidence SJC and LVK
will remain VFR through the TAF period. Low to medium confidence for
marine stratus to reach North Bay terminals, though TAFs hint at the
potential with SCT decks.
Vicinity of SFO...VFR with moderate onshore breezes into the
evening. Medium confidence on VFR conditions through the TAF period.
As described above, there is uncertainty on whether the southerly
surge of stratus will push through the Golden Gate and inland. If
the stratus makes it through the Golden Gate, it is possible for IFR
ceilings to reach OAK and SFO around the time of the SCT decks.
Leaned more on the optimistic side for this TAF period as the surge
was rather disorganized this morning and likely will be again
tomorrow morning.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Onshore winds follow their usual diurnal
pattern with VFR conditions prevailing. As mentioned previously, the
southerly surge of marine stratus will return overnight with SW
winds likely for MRY. SNS will remain more NW. Low-end IFR ceilings
will impact SNS first and then MRY between 06-10Z. Winds should
remain light overnight, but there is the potential for visibility
impacts around 4-6SM due to coastal drizzle/fog. Ceilings may also
intermittently drop down to LIFR given how compressed the marine
layer will be.
&&
.MARINE...
(Tonight through next Saturday)
Issued at 1215 PM PDT Mon Aug 3 2026
North to northwest winds continue to decrease from strong to fresh
into the evening, becoming moderate overnight. Strong gusts
persist in the far northern waters through the day before
diminishing this evening. In response, rough wind driven seas
continue to subside to moderate (4-7 feet) by tomorrow afternoon
and prevail thereafter.
&&
.FIRE WEATHER...
Issued at 1200 PM PDT Sun Aug 2 2026
Near critical fire weather conditions are expected through Monday
and after a period of elevated fire weather conditions, potentially
return later in the week. Temperatures remain around 10 to 15
degrees above normal across the interior through early next week
with highs in the upper 80s to 90s. No major changes to the
forecasted dry conditions. Daytime humidity retention remains poor
across the interior (20-30%) with humidity values dropping into
the 10s across the interior Central Coast, East Bay Hills/Valleys,
and the higher elevations. Portions of the interior Central Coast
may see daytime humidity values drop into the single digits
through the next couple of days. Overnight RH recovery remains
poor at locations above 2,000 feet with values between 25 to 40%
expected with some favored locations struggling to reach even 25%.
This will be particularly true across the Mayacamas, highest
peaks of the East Bay Hills, the Diablo Range, the Santa Cruz
Mountains, the Santa Lucia and Gabilan Ranges. Nocturnal drying
(rapid decrease in RH through the pre- dawn hours) may also
transpire which will increase the burn period or time in which
fire behavior may remain active. Energy Release Component (ERC)
values are projected to climb above the the percentile across the
interior Central Coast, Mid Coast to Mendocino (North Bay), and
Diablo- Santa Cruz (Diablo Mountains and Santa Cruz Mountains)
zones within the next two days. Diurnally breezy onshore winds are
expected along the coast, mountain gaps and passes, and along the
ridgelines each afternoon/evening. In addition, a burst of
offshore wind is forecast tonight into Monday morning for the SF
Bay Area and the North Bay, increasing the risk for nocturnal
drying events especially in downslope areas. With near critically
dry conditions and above normal temperatures expected, individuals
across these areas are advised to avoid activities that may spark
a fire. Fire crews are urged to exercise extra caution when
executing any prescribed burns, especially where fuels,
topography, and weather align.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 10 PM PDT this evening for CAZ504-510-
513>515.
PZ...Small Craft Advisory until 9 PM PDT this evening for Pt Arena to
Pt Reyes 10-60 NM.
Small Craft Advisory until 3 PM PDT this afternoon for Pigeon Pt
to Pt Pinos 10-60 NM.
&&
$$
SHORT TERM...KR
LONG TERM....KR
AVIATION...Navarrete
MARINE...Navarrete
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Prepared by Boulder-Creek.com Weather at: Mon Aug 3 14:30:02 PDT 2026
From the National Weather Service
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