FXUS66 KMTR 031140
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
440 AM PDT Mon Aug 3 2026
...New AVIATION, 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 1155 PM PDT Sun Aug 2 2026
(Tonight through Tuesday)
Upper level ridging builds over the eastern Pacific
and towards California while upper level troughing pushes across
southern CA and the intermountain west. Tonight, weak offshore flow
is set to develop over the Bay Area, which will lead to weak warming
and drying and keep the marine layer shallow. Models show it to be
around 500ft with any stratus development being confined to the
Monterey Bay and perhaps into the northern Salinas Valley. An otter
eddy is expected to form, which may pull it in and out of sites
periodically, with clouds mixing out by mid morning. After that,
sunny skies will prevail for much of the region leading to another
hot day for interior locations. Highs will generally be in the 90s
to near 105, with the hottest temperatures being found across the
interior locations for the Bay Area and Central Coast. For those
closer to the coast, San Francisco Bay, and Monterey Bay, the marine
layer should help keep temperatures manageable though the
gradient will be tight from the coast to just a few miles inland.
Look for highs ranging from the low to mid 60s to to mid 80s.
Widespread Moderate HeatRisk is expected across the interior
North Bay Mountains, the interior East Bay Valleys, the East Bay
Hills, the Santa Clara Valley, and the Santa Clara Hills. A Heat
Advisory has been hoisted for these conditions, which will run
from 10AM - 10PM Monday.
Here are some friendly reminders on how to beat the heat:
* 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.
&&
.LONG TERM...
Issued at 1155 PM PDT Sun Aug 2 2026
(Tuesday night through next Sunday)
Upper level high pressure gradually builds into the region this
week. Flow becomes a bit more onshore each day, with the marine
layer trying to deepen to around 500-1000ft by Wednesday. This
should allow temperatures to gradually step down for the next two-
three days, with a warming trend returning for the late portion of
the work week. Widespread Moderate HeatRisk returns, with perhaps a
few patches of Major Heatrisk in the East and South Bay if the
trends holds. For now, confidence is too low to issue any sort of
heat products that far out but it will be something to watch over
the next day or so.
&&
.AVIATION...
(12Z TAFS)
Issued at 429 AM PDT Mon Aug 3 2026
VFR everywhere except the Monterey Bay region. Satellite shows a
southerly surge of stratus taking place along the coast but
confidence is low that it will reach interior Bay Area airports.
IFR conditions are expected to continue at MRY and SNS through
late this morning before VFR returns. There is mixed confidence
for tonight's stratus forecast with models suggesting a more
widespread return tonight. If the southerly surge holds together
than more widespread stratus is likely, but, with the upper level
ridge rebuilding and compressing the marine layer it seems
unlikely that stratus would be widespread across the region. For
the 12Z TAFs went more optimistic and kept stratus over only the
Monterey Bay region for tonight.
Vicinity of SFO...VFR. Guidance shows some potential for patchy
stratus this morning and again tonight but confidence is low.
Breezy onshore winds return this afternoon/evening before winds
decrease overnight.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...IFR conditions continue through late this
morning. Confidence is low to moderate on the timing of stratus
return tonight. Models are indicating an earlier return is
possible around 03/04Z. It has indicated that trend for the last
few days but stratus has consistently not arrived until ~08/09Z.
Opted to go with persistence for a later return of stratus but
this may need to be adjusted depending how well the southerly
surge of stratus holds up offshore. If the stratus bank is able to
hold together offshore an earlier return of stratus becomes more
likely across the Monterey Bay region.
&&
.MARINE...
(Today through Saturday)
Issued at 429 AM PDT Mon Aug 3 2026
Strong north to northwesterly winds will gradually decrease
through this evening. Occasional gale force gusts remain possible
across the far northern outer waters through late this morning.
Rough to very rough seas (10-15 ft) will subside to moderate by
Tuesday evening. Moderate seas (4-6 ft) continue midweek through
the remainder of the work week.
&&
.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 from 10 AM this morning to 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...Kennedy
MARINE...Kennedy
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Prepared by Boulder-Creek.com Weather at: Mon Aug 3 06:30:02 PDT 2026
From the National Weather Service
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