FXUS66 KMTR 140447
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
947 PM PDT Fri Mar 13 2026
...New AVIATION...
.KEY MESSAGES...
Updated at 244 PM PDT Fri Mar 13 2026
- Above normal temperatures and Minor HeatRisk continue through
Saturday
- A long duration, early season heatwave begins Sunday with
record breaking temperatures and Moderate HeatRisk expected
Monday through late week
- Elevated potential for grass fires due to warm and dry
conditions and periods of moderate offshore winds next week
&&
.UPDATE...
Issued at 905 PM PDT Fri Mar 13 2026
Strong 500 mb height ridging at 581 decameters on the evening
Oakland upper air sounding has decreased a little since morning.
Weak upper level jet stream divergence and cirrus clouds continue
to move across the forecast area within the medium to broad ridge.
The sounding vertical water vapor distribution is dry at 0.36"
precipitable water. The dryness in the vertical has helped nightly
coastal stratus/fog formation thanks to radiative cooling above
the marine layer. The marine layer is currently ~ 1000 feet deep.
The 850 mb temperature on the evening sounding is warm already at
15.2 Celsius which is greater than the 90th percentile for mid
March. After a cool to chilly start it did warm up above mid March
30 year normal highs today, but not to the extent it could've
warmed if air parcels aloft were compressed closer to the surface
and fully mixed vertically with March daytime surface warming. This
combination however has a better chance of occurring beginning early
next week which will cause daytime temperatures to warm up rapidly
to well above normal and record territory once the sun rises. There
is good agreement in the model forecasts showing strong long wave
ridging becoming highly focused over the southwestern U.S. while on
the periphery the singular high is surrounded by low pressure
development downstream and upstream. Late Saturday night and Sunday
in fact the WMC-SFO pressure gradient (offshore winds) will
temporarily steepen to ~ 10 mb while the 850 mb temperature won't be
at its forecast peak quite yet for next week. This may be a good
thing that it's out of step from a warming potential for Sunday. 850
mb temperatures then climb next week while the WMC-SFO pressure
gradient eases.
Overall as advertised expect warmer to much warmer daytime highs
next week. 500 mb wave amplification will take place and it may
take much of next week before the high has a chance to move and/or
weaken any. There's been some consistency in the GFS showing
upstream movement may be a little quicker to arrive here than what
recent ECMWF has shown. This may make a difference in when cooler
air returns here later next week.
No updates to the forecast anticipated this evening.
&&
.SHORT TERM...
Issued at 244 PM PDT Fri Mar 13 2026
(This evening through Saturday)
Pleasant, above normal temperatures are expected across the region
today with forecasted highs running 10-15 degrees above normal.
However, there is one caveat to today's high temperatures: cloud
cover. Satellite shows high level clouds streaming across much of
the Bay Area and Central Coast while a shallow marine layer is
bringing low level clouds directly along the coastline. The shallow
marine layer is keeping temperatures cool along the coast with both
HAF and MRY at 55 degrees as of 1PM. Temperatures are a bit higher
(mid to upper 60s) across inland areas where low level clouds have
cleared. Made some tweaks to the high temperature forecast for today
and bumped afternoon highs down to the low 60s directly along the
coast to account for the persistent shallow marine layer. Generally
expecting temperatures to peak in the mid to upper 70s across the
interior today before cooling down into the upper 40s to low 50s
tonight. If you have any outdoor activities today and Saturday will
be the best days for them as they are the two coolest days of the
upcoming forecast period.
&&
.LONG TERM...
Issued at 244 PM PDT Fri Mar 13 2026
(Saturday night through next Thursday)
Upper level ridging builds in across the region Saturday before
fully settling in by late weekend. Temperatures on Saturday will be
fairly similar to those observed on Friday with highs in the upper
70s to low 80s across the interior and 60s directly along the
coastline. Both HREF and WRF guidance suggest a shallow (500 ft)
marine layer is possible again Saturday morning which will keep
coastal areas cooler than interior areas.
Saturday will generally be the last "pleasant" day of the Long Term
forecast. By Sunday, the center of the upper level ridge will push
into California and usher in the start of our prolonged heat wave.
The center of the upper level ridge will then remain over the
California/Arizona border through late next week, potentially
sticking around into next weekend. This unusually strong ridge is
bringing us late summer like weather with 500mb heights around 5900
meters. Sunday will act as a transition day between the more
pleasant Saturday temperatures to full summer on Monday with highs
in the upper 70s to mid 80s. Starting Monday, highs across the
interior will rise into the upper 80s to 90s. It will then stay that
hot through the remainder of the long term forecast. This has the
potential to break numerous daily high temperature records and even
some all time high temperature records for March.
It is worth noting that temperatures may in fact go up during the
second half of the week (starting Wednesday) as the ridge
strengthens further. The NBM 95th Percentile (a reasonable high end
scenario) pushes temperatures into the upper 90s to low 100s across
the interior Central Coast and portions of the Santa Cruz
Mountains/interior valleys Wednesday through late week. There is
enough supporting evidence to say that this heatwave will extend
through Friday and likely into the weekend given the longevity and
restrengthening of the upper level ridge. Currently, Moderate
HeatRisk is only forecast Monday through Wednesday but this is
likely to expand through the rest of the week as the temperature
forecast continues to increase. If you are spending any time
outdoors this week, remember to drink plenty of water and allow your
body to rest as needed. This heatwave is a marathon not a sprint
with overnight conditions to offer at least some respite from
daytime heat. Heat Advisories are likely to be issued for much of
the urban areas and adjacent Santa Cruz Mountains/Diablo Range
starting Monday and continuing through late week. For now, we are
not anticipating issuing an Extreme Heat Watch/Warning as overnight
temperatures will cool enough to prevent us from reaching Extreme
Heat criteria. We will, however, need to keep a close eye on the
forecast for the second half of the week as models are signaling
that it could be even warmer than the first half.
As small, fine fuels (grass) cure this week, the potential for grass
fires will increase. Offshore winds will remain light to moderate
which will help mitigate how much any fires that do develop can
grow. If you are participating in any outdoor activities (camping,
offroading, hiking, etc) exercise caution when using fire and be
aware that the risk of grass fires will be elevated next week.
&&
.AVIATION...
(06Z TAFS)
Issued at 946 PM PDT Fri Mar 13 2026
Winds are starting to reduce, becoming light for most areas aside
from the immediate coast. This means HAF will continue to see
moderate winds through the night. Low CIGs look to form in the late
night around the Monterey Bay as well as at HAF, then STS looks to
have moments of low CIGs and mist into Saturday morning. Moderate
winds return Saturday afternoon for most areas, while the coast (and
HAF) see strong gusts. Cloud cover erodes into the afternoon, but
hazy conditions look to form in most of the valleys and along the
coast into the weekend. Winds reduce again into Saturday night.
Vicinity of SFO...VFR through the TAF period. Moderate west winds
linger into the night before reducing. Northwest winds build again
into Saturday afternoon and last into late that night before
becoming light again.
SFO Bridge Approach...Scattered low clouds look to move around the
Eastern SF Bay into Saturday morning, with a few passing through the
approach until the late morning.
Monterey Bay Terminals...VFR lasts into the night before winds
become light and IFR CIGs arrive to MRY. IFR CIGs will be slower to
arrive to SNS, but are expected into early Saturday morning while
MRY begins to see moments of LIFR CIGS. Expect some mist and reduced
visibilities along with the building cloud cover. VFR returns in the
mid to late morning as moderate west to northwest winds build. Winds
reduce again into Saturday night.
&&
.MARINE...
(Tonight through next Wednesday)
Issued at 842 PM PDT Fri Mar 13 2026
Fresh to moderate north/northwest breezes Continue across the
waters causing hazardous conditions through the weekend. Winds
and seas ease in the inner waters by Sunday afternoon, and the
rest of the waters by mid Monday. Mostly calm conditions will
then last through the rest of the forecast period.
&&
.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 Pigeon Pt to Pt
Pinos 0-10 nm-Pt Arena to Pt Reyes 0-10 nm-Pt Pinos to Pt
Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.
Small Craft Advisory until 9 PM PDT Sunday for Pt Arena to Pt
Reyes 10-60 NM.
Small Craft Advisory until 9 AM PDT Sunday for Pigeon Pt to Pt
Pinos 10-60 NM.
&&
$$
SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...Murdock
MARINE...Murdock
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Prepared by Boulder-Creek.com Weather at: Sat Mar 14 00:30:03 PDT 2026
From the National Weather Service
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