FXUS66 KMTR 031833
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1133 AM PDT Mon Aug 3 2026

...New AVIATION...

.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. 

&&

.UPDATE...
Issued at 941 AM PDT Mon Aug 3 2026

Satellite imagery this morning and current windfield along the
coast shows a semi-southerly surge. Low clouds continue to sneak
farther north up the coast near Pt Reyes. We even see a few 
clouds up the Salinas Valley. Inland clouds will roll back to the 
coast by this afternoon, but clouds will linger along the coast. 
As noted below the bigger weather impact for today will be the 
Heat. No update with current Heat Advisories as they remain valid 
for interior N and E Bay. Finally, one other highlight this 
morning with the southerly surge is what's happening above the 
surge.  over the higher terrain showed critically low humidity 
with several sites in the single digits. This is a solid example 
of nocturnal drying where humidity recovers early in the night 
then dry toward sunrise. Therefore, critical fire weather 
conditions exist. 

No update need this morning, but will be monitoring the heat and
fire weather conditions through the day.

MM

&&

.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...
(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...
(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 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...Kennedy

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Prepared by Boulder-Creek.com Weather at: Mon Aug 3 12:30:03 PDT 2026