FXUS66 KMTR 181958
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1258 PM PDT Mon May 18 2026

...New SHORT TERM, LONG TERM, FIRE WEATHER...

.KEY MESSAGES...
Updated at 1251 PM PDT Mon May 18 2026

 - Breezy to windy conditions, especially across the North, East,
   and South Bay Mountains and the Santa Cruz Mountains continue
   through tonight

 - Elevated fire weather concerns continue through today across
   the interior due to very dry conditions and breezy winds

 - Above normal temperatures continue through midweek with seasonal
   temperatures returning late week

&&

.SHORT TERM...
Issued at 1251 PM PDT Mon May 18 2026
(This evening through Tuesday)

Gusty offshore winds have started to come down across the region and 
will continue to ease through the remainder of the day. Current 
gusts across the lower elevations are peaking around 25-30 mph with 
gusts across the higher elevations peaking between 35-45 mph. The 
strongest gust observed during this wind event was 86 mph right 
around midnight at Mt. Umunhum where the station is at an elevation 
of 3319 feet. This tracks pretty well with when the SFO-WMC pressure 
gradient peaked (-7.60 mb) around 1AM and again around 5AM. The SFO-
WMC gradient is currently around -4.3 mb and is expected to continue 
easing through the remainder of the day. Winds remain lightly 
offshore across the interior through the remainder of today into 
tomorrow but winds will be weaker. We will see a return to our 
normal breezy afternoon/evening winds that ease overnight starting 
Tuesday. 

Upper level ridging continues to dominate the Pacific Ocean while 
broad upper level troughing prevails over the Western United States. 
At the surface, high pressure prevails over the Pacific while a 
coastal trough develops along the California coast. Warmer 
temperatures are expected to continue Tuesday through Thursday. This 
is thanks both to ridging offshore suppressing the marine layer and 
a warmer, drier airmass moving in in the wake of this weekend's 
strong offshore winds. Interior high temperatures will generally be 
in the 80s with the hottest portions of the North and East Bays in 
the low 90s. Coastal areas will be slightly cooler in the 60s to mid 
70s. Dry conditions are expected to prevail through much of the 
upcoming week with daytime relative humidity values dropping into 
the 10's to 20's. While fire weather concerns are lower now that the 
winds are easing, fine fuels (grass, shrubs) are dried out and are 
ready to burn. If you are engaging in any outdoor activities 
involving flames or are towing something, keep a close eye on it and 
prevent sparks from spreading.

&&

.LONG TERM...
Issued at 1251 PM PDT Mon May 18 2026
(Tuesday night through next Sunday)

The overall pattern remains the same for much of the upcoming week. 
High temperatures will stay above seasonal normals through Thursday 
with highs in the 80s to low 90s across the interior and 60s to 70s 
along the coast. Patchy moderate heatrisk is forecast across urban 
areas but it is note widespread enough to necessitate a Heat 
Advisory. If you are spending time outdoors this week make sure to 
drink plenty of water and take breaks in the shade as needed. Winds 
generally remain offshore with diurnally breezy conditions expected. 
Friday into the weekend a pattern change looks likely. Long range 
guidance suggests upper level ridging will weaken and shift westward 
over the Pacific while broad upper level troughing dominates the 
West Coast. With high pressure shifting away, onshore winds return 
and the marine layer will be able to redevelop by late week. A 
shallow (~500 ft) marine layer will redevelop mid to late week but 
will deepen to ~1000 ft by Friday. This, and receding high pressure, 
will kick off a cooling trend with interior temperatures returning 
to the 70s to low 80s and coastal areas to the 60s. The return of 
the marine layer will help to alleviate dry daytime conditions, 
further reducing fire risk late next week. &&

.AVIATION...
(18Z TAFS)
Issued at 1021 AM PDT Mon May 18 2026

VFR conditions prevail through the TAF period. Breezy and gusty 
northeast winds will gradually diminish through the next couple of 
hours as an onshore push returns to the coastal regions this 
afternoon, with the coastal breeze continuing through the evening. 
Breezy winds will continue across the interior mountains of the Bay 
Area through the night, with northeast winds spreading across the 
interior valleys Tuesday morning towards the end of the 24-hour TAF 
period. Beyond that, Tuesday's coastal breezes look to be stronger 
than today's.

Vicinity of SFO... VFR conditions through the TAF period. Breezy and 
gusty northeast winds will turn more northwesterly through the 
afternoon, before diminishing through the evening and remaining 
light overnight through Tuesday morning. West-northwest winds will 
resume on Tuesday afternoon.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... VFR conditions through the TAF period. 
Breezy northwest winds will develop imminently and continue into the 
evening. Winds remain light overnight before resuming Tuesday 
afternoon after the end of the TAF period.

&&

.MARINE...
(Today through Saturday)
Issued at 1021 AM PDT Mon May 18 2026

Winds continue to diminish throughout the marine environment, but
moderate to rough seas and moderate to fresh northwest breezes
will still offer hazardous conditions for small craft into the mid
weak before easing for most zones. Fresh to strong northwest
breezes will remain hazardous for small craft into the late week
for the northern outer zone.

&&

.FIRE WEATHER...
Issued at 1251 PM PDT Mon May 18 2026

Gusty north to northeast winds will continue through this
afternoon before easing tonight into tomorrow. Peak gusts between
35 to 45 mph are still possible across the higher elevations into
this evening. Daytime humidity retention remains poor with most
sites staying around 10-25% across the interior and higher peaks
with limited overnight recoveries. Winds ease by Tuesday but fire
weather concerns will linger through late week as light offshore
flow continues and daytime humidities remain poor.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory until 3 AM PDT Tuesday for CAZ506.

PZ...Small Craft Advisory until 3 PM PDT this afternoon for SF Bay N 
     of Bay Bridge.

     Small Craft Advisory until 9 PM PDT this evening for Mry Bay-
     Pigeon Pt to Pt Pinos 0-10 nm.

     Small Craft Advisory until 3 AM PDT Tuesday for Pt Arena to Pt 
     Reyes 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

     Small Craft Advisory until 9 PM PDT Wednesday for Pt Arena to Pt 
     Reyes 10-60 NM.

     Small Craft Advisory until 9 AM PDT Tuesday for Pigeon Pt to Pt 
     Pinos 10-60 NM.

&&

$$

SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...DialH
MARINE...DialH

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Prepared by Boulder-Creek.com Weather at: Mon May 18 14:30:03 PDT 2026