FXUS66 KMTR 271922
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1222 PM PDT Thu Aug 27 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 1201 AM PDT Thu Aug 27 2026

 - Slight chance of thunderstorms this morning, with shower
   chances through Friday

 - Slight cooling today, with temperatures close to seasonal averages

 - Cooling trend continues Friday into the next week

&&

.UPDATE...
Issued at 725 AM PDT Thu Aug 27 2026

Have updated the forecast to include a slight chance of 
thunderstorms through 10 AM this morning for the Central Coast. This 
is as we are seeing thunderstorms offshore and moving into Santa 
Barbara and San Luis Obispo counties. While there still appears to 
be limited instability across the Central Coast, we have added them 
due to the convection offshore. We will continue to monitor this 
closely throughout the day. 

RGass

&&

.SHORT TERM...
Issued at 1201 AM PDT Thu Aug 27 2026
(Today and tonight)

Stratus clouds are developing at the immediate coast and are 
expected to generally remain confined to the coastal valleys 
overnight before mixing out through Thursday morning. Zooming out 
into the Pacific reveals some interesting activity off the coast as 
some storm cells with frequent lightning have developed around a 
moisture gradient. The latest forecast update includes a slight 
chance for thunderstorms for the morning hours, around the time 
that these cells would impact the coast if they hold together. As 
of the time of writing, they have been dissipating as they move 
towards our coastal waters, but the night shift will continue 
monitoring these cells as they approach and issue any forecast 
updates and products as they become necessary. Beyond the morning 
hours, tropical moisture sourced from the remnants of Tropical 
Storm Iselle will come into the state, and slight chances for 
showers persist through the day. Low, but non-zero, chances for 
thunderstorms will tick up again in the afternoon and evening 
hours, but the limiting factor appears to be insufficient 
atmospheric instability. Will continue to monitor the situation as
it evolves through the day.

The large-scale weather pattern remains dominated by the balance 
between the ridging over the Desert Southwest and the troughing over 
the eastern Pacific. The ridging has generally won out over the last 
few days, but today will mark the very beginnings of a transition to 
a more troughing-dominated pattern. Temperatures will remain near to 
slightly above the seasonal averages, but we will see a slight 
cooldown as highs reach the upper 80s to middle 90s inland, the 
upper 90s to the triple digits in the warmest interior locations, 
the lower 70s to the lower 80s near the Bays, and the lower to 
middle 60s at the Pacific coast. Breezy onshore winds will develop 
in the afternoon and evening hours with gusts of 20 to 30 mph at the 
coasts.

For a discussion of weather-related impacts to the fire weather 
situation, see the FIRE WEATHER section.

&&

.LONG TERM...
Issued at 1201 AM PDT Thu Aug 27 2026
(Friday through Wednesday)

The progression of the trough, and with it the cooling trend and 
associated tropical moisture, continue into Friday with the slight 
chances for showers continuing through the day. Later on Friday into 
the weekend, the tropical moisture dips to the south but the 
deepening trough remains, and cooler temperatures continue into the 
middle of next week. Temperatures reach their coolest on Monday, 
around 5 to 15 degrees below seasonal averages, as high reach the 
70s throughout the inland valleys, the 80s along the warmest 
interior Central Coast regions, and the upper 50s to the 60s at the 
Bays and the Pacific coast. The trough will start to flatten out, 
but remains in place with temperatures slow to rise. The forecast 
shows rain chances returning to the region for the middle of next 
week, but this is critically dependent on how conditions evolve in 
the tropical Eastern Pacific, so confidence remains low.

&&

.AVIATION...
(18Z TAFS)
Issued at 1222 PM PDT Thu Aug 27 2026

Quite an interesting set up today. A moisture plume is moving across 
our region from the southwest and is producing lightning offshore as 
well as some light rain. Whether rain will reach the ground over the 
terminals is uncertain, but high confidence for virga at the very 
least. Overall, there is low confidence on the forecasted ceilings 
towards the end of the TAF period and exact timing of potential 
vicinity showers, but medium confidence for it to remain south of 
the Golden Gate. The potential for lightning to impact terminals 
this TAF period is low, around a 10-15% chance, and TAFs will be 
updated as needed.

Despite the current set up, VFR conditions prevail through the day 
with a parade of high level clouds associated with the high-based 
convective system. Moderate onshore breezes increase through the day 
and ease overnight. If thunderstorms do develop over land, we will 
monitor for gusty outflows and amend as needed.

Vicinity of SFO...VFR through the afternoon with onshore winds 
increasing to 15-20 kt and ease to around 10 kt overnight. SFO and 
OAK are currently on the edge of the previously mentioned convective 
system, so there is not an immediate concern for lightning or VCSH. 
However, this moisture plume is expected to become a bit more 
widespread early Friday morning. As of writing this, there is a 
great deal of discrepancy in model guidance, so the timing will be 
refined in following TAF issuances.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Moderate onshore winds prevail this 
afternoon and ease overnight. MRY and SNS have the highest chance of 
remaining under the influence of the moisture plume this TAF period. 
MRY may be close enough to the coast to still experience some marine 
influence, but medium confidence on the timing of IFR ceilings. 
Lightning is still being observed via satellite offshore and will 
continue to be monitored. 

&&

.MARINE...
(Tonight through next Tuesday)
Issued at 1222 PM PDT Thu Aug 27 2026

Fresh northwest breezes with occasional near gale force gusts
persist through the weekend and ease by early next week. Wind
driven  seas remain moderate into next week as a long period
southerly swell  around 16 to 18 seconds approaches our coastal
waters by Friday  morning.

&&

.FIRE WEATHER... 
Issued at 1201 AM PDT Thu Aug 27 2026

One more day of near-critical fire weather conditions above 1000 
feet, especially across the Central Coast, as warm and dry 
conditions continue above the marine layer inversion and overnight
humidity recoveries remain poor. One thing to note is that even 
with the slight chance of rain today into Friday, we are not 
expecting wetting rains to develop, while a small but non- zero 
chance for thunderstorms raises the specter for a dry lightning- 
induced fire start in the higher elevations. Across the Timber and
Plaskett Fires, light offshore winds overnight may lead to 
nocturnal drying concerns at the higher elevations. A pattern 
change Friday into the weekend will bring cooler temperatures and 
likely a deeper marine layer, bringing progressively more relief 
to some of the higher elevations. 

DialH

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Red Flag Warning from 5 AM to 3 PM PDT Friday for CAZ512-516-517-
     528>530.

PZ...Small Craft Advisory until 2 PM PDT Friday for Pigeon Pt to Pt 
     Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt 
     Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM-Pt Pinos to Pt 
     Piedras Blancas 0-10 nm.

     Small Craft Advisory from 3 PM Friday to 9 AM PDT Saturday for 
     Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 
     NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 
     NM-Pt Pinos to Pt Piedras Blancas 0-10 nm.

&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Navarrete
MARINE...Navarrete

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, X, and YouTube at:
www.facebook.com/nwsbayarea
x.com/nwsbayarea
www.youtube.com/nwsbayarea


  
Prepared by Boulder-Creek.com Weather at: Thu Aug 27 12:30:03 PDT 2026