FXUS66 KMTR 131601
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
901 AM PDT Fri Mar 13 2026

...New UPDATE, MARINE...

.KEY MESSAGES...
Updated at 1229 AM PDT Fri Mar 13 2026

 - Above normal temperatures and minor HeatRisk continue through 
   Saturday

 - A sharp warm-up Sunday through Monday will kick off an early
   season heat wave with record breaking temperatures and moderate
   HeatRisk next week

 - Elevated potential for grass fires due to warm and dry 
   conditions and periods of moderate offshore winds next week

&&

.UPDATE...
Issued at 901 AM PDT Fri Mar 13 2026

Locally foggy conditions along the coastline are beginning to 
dissipate with visibility to improve through the remainder of the
morning. Increased cloud cover across the region has kept 
temperatures this morning a few degrees cooler than they were at 
this time yesterday. Still expecting highs today to be 10-15 
degrees above normal with most interior locations in the mid to 
upper 70s. Minor HeatRisk is forecast across the CWA today which 
primarily effects those who are extremely sensitive to heat or 
without access to cooling/hydration.

&&

.SHORT TERM...
Issued at 1229 AM PDT Fri Mar 13 2026
(Today and tonight)

Cirrus clouds are moving over the CA coast associated with a sharp
upper level trough over the Eastern Pacific. This feature is
producing southerly winds that are pumping upper level moisture
from the tropics to the West Coast. These clouds will likely
remain trough the day as the trough slowly weakens and meanders a
little closer towards the coast. This will help moderate the
temperatures today, but the moderate strength upper level ridge
will keep max temperatures similar to yesterday and around 10-15 
degrees above normal.

&&

.LONG TERM...
Issued at 1229 AM PDT Fri Mar 13 2026
(Saturday through Thursday)

Saturday's temperatures will be similar to Friday, but for a
different reason. The high clouds will clear, but a very weak
disturbance will take a quick bite out of the ridge. 500mb 
heights are expected to drop from around 5850m on Friday to around
5770m on Saturday morning. That's still well above normal (5650m)
for this time of year. The ridge starts to rebuild Saturday 
afternoon while surface high pressure builds over the northern Rockies
causing the winds to veer offshore. This upper level ridge will
continue to build through Tuesday, eventually becoming as strong
as we ever seen in March. Some high clouds are likely to return 
Sunday before clear skies and unfiltered heat moves in for the 
peak of the heat wave starting Monday. Tuesday and Wednesday look 
like the hottest days before the ridge axis moves through. This 
will cause the temperatures to drop a couple degrees, but the heat
wave will persist through the workweek. More noticeable relief 
will have to wait until the weekend, but temperatures may not 
return to normal for the rest of the month.

The guidance on the strength of this heat wave is remarkable. I'm
going to cover it in detail here, but the bottom line is that I 
audibly gasped when I saw the ECMWF Extreme Forecast Index for 
maximum temperatures next week. I have never seen it anywhere 
near this aggressive with bright red painted across the state. 
That means the ECMWF ensemble members are showing a 99-100% chance
of exceeding the maximum values of M-Climate (20-year database). 
The upper level support strongly points record breaking heat. 
There is a 75% chance that the 500mb height will break 5900m 
Monday evening (March record: 5885m). There is also a 75% chance 
the 850mb temp will break 20C Tuesday - Wednesday (March record: 
19.2C). The 250 mb height is very likely to set a monthly record
as well. All of this upper level support, combined with offshore
winds, creates the perfect recipe for record breaking heat. As
such, we expect a slew of daily records to be broken, and several
monthly records are likely to go down as well. One final note on
the upper level statistics before the hype train runs off the
rails; these numbers are very high for March (near the lowest 
heights climatologically), but would be typical for early August. 
As such, expect next week to feel like early August, just without 
the marine layer.

So what does this mean for you? Temperatures will be warm but
comfortable through Saturday with mid to upper 70s inland and
upper 60s along the coast, roughly similar to what we saw on 
Thursday. By Sunday temperatures jump 5-10 degrees before another 
similar increase Monday. During the peak of the heat wave on 
Tuesday and Wednesday, most areas will be in the upper 80s and 
90s, including many coastal locations thanks to the offshore 
winds. Temperatures will likely drop a couple degrees later in the
week, but not nearly enough to end the heat wave. Much of the 
area will be under moderate HeatRisk. This level affects people 
sensitive to the heat, especially those without access to cooling
and hydration. Keep in mind this is our first heat wave of the 
year and we haven't seen these temperatures since September.

&&

.AVIATION...
(12Z TAFS)
Issued at 435 AM PDT Fri Mar 13 2026

Upper level moisture riding the ridge is leading to widespread
cirrus over the region this morning (SCT-BKN150-250). As the
surface, a quasi-marine layer trying to reforming, but it is
struggling. VFR most terminals this morning except HAF/MRY with
stratus and STS with some patchy fog. Some stratus will linger for
HAF, but elsewhere will be VFR today. Stronger onshore flow will
lead to some breezy conditions at times. Expect a repeat again
tonight into Saturday with some marine stratus impacting the 
immediate coast and pushing locally inland. 

Vicinity of SFO...Breezy NW flow through the GAP with a few low
clouds around 500 ft thru AM rush. VFR this afternoon. Didn't buy
in on cigs for tonight, but guidance does have some lower cigs
with a 20-25% chc of MVFR conditions.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Low/patchy cigs for MRY. There will be
pockets of clearing through 17Z at times. Low cigs again tonight
for MRY.

&&

.MARINE...
(Today through Wednesday)
Issued at 901 AM PDT Fri Mar 13 2026

Fresh to moderate north/northwest breezes will persist through
the weekend. Periods of stronger winds will result in locally
hazardous conditions. Both winds and seas will begin to ease late
Sunday night into the beginning of next week.

&&

.CLIMATE...
Issued at 614 PM PDT Thu Mar 12 2026

The following are the record high temperatures at the long term
sites for March 15th, 16th, 17th and 18th.

Location         Mar 15      Mar 16      Mar 17      Mar 18

Santa Rosa       88 in 2004  91 in 2004  87 in 1996  84 in 2010
San Rafael       83 in 1972  87 in 1972  84 in 1972  80 in 1996
Kentfield        85 in 2004  86 in 2004  87 in 1914  89 in 1914
Napa             86 in 2004  88 in 2004  92 in 1914  87 in 1914
Richmond         85 in 2004  84 in 1972  83 in 2004  78 in 1996
Livermore        83 in 1972  88 in 1972  87 in 1972  86 in 2004
San Francisco    82 in 2004  85 in 1914  85 in 1914  86 in 1914
SFO Airport      81 in 2004  82 in 2004  82 in 2004  77 in 2004
Redwood City     84 in 2004  84 in 2004  85 in 2004  84 in 2004
Half Moon Bay    74 in 1974  78 in 1972  83 in 2004  75 in 1978
Oakland Museum   85 in 2004  85 in 2004  85 in 2004  81 in 2004
San Jose         82 in 2004  85 in 1914  88 in 1914  87 in 1914
Salinas Airport  83 in 1972  87 in 2004  87 in 2004  84 in 1960

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Sunday for Pt Arena to Pt 
     Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory from 3 PM this afternoon to 3 AM PDT Sunday 
     for Pt Reyes to Pigeon Pt 0-10 nm.

     Small Craft Advisory from 9 PM this evening to 3 AM PDT Sunday 
     for Pigeon Pt to Pt Pinos 0-10 nm.

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

&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...MM
MARINE...JM

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: Fri Mar 13 10:30:03 PDT 2026