FXUS66 KMTR 200510
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1010 PM PDT Sun Jul 19 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 148 PM PDT Sun Jul 19 2026

 - Near or slightly below normal temperatures and higher humidity
   through the first half of the upcoming week.

 - The marine layer and mid to upper level cloud cover will
   continue to help keep temperatures cooler under building high
   pressure.

 - Approximately 5% chance of elevated showers with isolated 
   thunderstorms Tuesday afternoon through Wednesday evening.

&&

.SHORT TERM...
Issued at 148 PM PDT Sun Jul 19 2026
(This evening through Monday night)

Marine layer stratus has retreated back to the coastline as of early 
this afternoon. Increasing coverage of mid/high level clouds 
streaming northeast out ahead of an upper level low over the EPAC 
will continue this afternoon and tonight. Elevated showers can be 
seen on radar approaching our southern outer marine zones and will 
continue to remain well off shore for the remainder of today and 
this evening. However, after midnight, elevated shower activity is 
possible mainly for the Bay Area and the North Bay through mid-
morning Monday. Poor lapse rates and thermal instability will limit 
the chances for thunderstorm activity. Along with the weak 
instability, very dry air between 700mb-925mb will likely result in 
little to no precipitation reaching the ground with only a trace to 
a few hundredths where any rainfall is measured. Temperatures on 
Monday will be similar to slightly cooler than todays values with 
the increased cloud coverage. 

Expecting a typical stratus intrusion tonight into early Monday 
morning as onshore flow persists, with high clouds helping to limit 
some of the radiational stratus cloud top cooling that will result 
in less mist/drizzle coverage than we saw this morning, and mostly 
confined to coastal areas.

&&

.LONG TERM...
Issued at 148 PM PDT Sun Jul 19 2026
(Tuesday through next Saturday)

Chances for another round of elevated showers with isolated 
thunderstorms is trending upward. Not currently reflected in the 
official forecast but subsequent updates may see increases in 
coverage and intensity by Tuesday afternoon into Wednesday, mainly 
across the North Bay and maybe as far south as the Bay Area. The 
main source continues to be the moisture associated with what will 
be the remnants of Elida moving north, well offshore of our area by 
the end of the day Wednesday. Increasing lift, better thermal 
instability and slightly improved mid-level lapse rates between 7-
7.5 C/km by late Tuesday afternoon into Tuesday night will provide 
the best chances for elevated thunderstorms and potentially 
impactful dry lightning. A similar pocket of dry air from 700mb-
925mb will continue to limit beneficial rainfall. A final wave of 
elevated instability will move into the North Bay once again late
Wednesday afternoon into the evening hours with potentially 
improved thermal instability, however less lift and weaker lapse 
rates, with dry air in the mid-levels continuing to limit 
precipitation reaching the ground. By Thursday into the weekend, 
the increased mid-level moisture shifts north and we begin to see 
drier air aloft with a gradual warming trend into the weekend. 
However, onshore flow will persist will persist through the 
extended forecast with typical no- sky-July conditions each night 
and morning.

&&

.AVIATION...
(06Z TAFS)
Issued at 1000 PM PDT Sun Jul 19 2026

High clouds are obscuring low level stratus across the region but
observations and cameras indicate it is starting to move inland. 
Pushed back the timing of stratus arrival for Bay Area sites 
slightly with the thinking being high clouds are slowing down the 
arrival of low level stratus. Confidence is mixed as to if stratus
will reach SJC and LVK so have included a tempo for stratus at 
SJC but not at LVK. Stratus is forecast to start out MVFR but will
compress to IFR overnight. LIFR conditions and fog are possible 
along the coastline. Conditions improve by late morning with the 
exception of the coast where some models indicate stratus could 
linger through the entire day. The marine layer compresses to 
around 1000 ft tonight (and again tomorrow night) so we can expect
stratus to return late tomorrow evening for most sites. Diurnally
breezy onshore winds continue.

Vicinity of SFO...High clouds are streaming into the Bay Area with
cameras showing stratus approaching SFO. Highest confidence in
stratus making it to SFO around 08Z but it may arrive as early as
06Z. Most likely MVFR CIGs but IFR CIGs may temporarily develop 
during the early morning hours. Clearing will take place by the 
late morning and remain VFR through the rest of the day. Models 
indicate some potential for stratus to return tomorrow night but 
confidence is mixed this far out given the compressing marine 
layer and high level clouds.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...LIFR conditions to persist through the
late morning with some potential for reductions in visibility and
fog overnight. Highest confidence in reduced visibilities to
around 2-3SM but the LAMP model does show dense fog developing
during the early morning hours. Clearing will take place by late
morning with SNS around 17Z and MRY around 19/20Z before stratus
returns early that evening. The MRY TAF is on the more optimistic
side in terms of clearing with LAMP guidance keeping stratus over
the site through the entirety of tomorrow.

&&

.MARINE...
(Tonight through next Saturday)
Issued at 1000 PM PDT Sun Jul 19 2026

Slight to moderate seas and a gentle to moderate northwesterly
breeze will persist through the upcoming workweek. Long period
southerly swell is forecast to increase due to tropical cyclone
activity across the Eastern Pacific. Southerly swell heights are
anticipated to remain in the slight category but mixed seas may
result in hazardous boating conditions through the week.
Additionally, there are non-zero chances for high based showers
which could result in pockets of gusty outflow winds and
subsequent steep seas now through mid-week.

&&

.FIRE WEATHER...
Issued at 148 PM PDT Sun Jul 19 2026

Near to slightly cooler than normal temperatures will continue 
through the week with typical diurnal intrusion of the marine layer 
each night and retreat to the coast each morning as onshore flow 
persists. However, above 1500-2000ft we'll see relatively weak 
thermal belting the first half of the week with continued warm 
overnights and poor RH recovery at higher elevations.

Guidance is trending toward an increasing potential for elevated 
showers and isolated thunderstorms Tuesday afternoon through 
Wednesday evening. Chances are below 5% in the official forecast but 
may increase in subsequent updates tonight and Monday. The 
primary concern is dry lightning strikes across the North Bay, 
with lesser chances farther south into the Bay Area.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&

$$

SHORT TERM...JM
LONG TERM....JM
AVIATION...Kennedy
MARINE...Kennedy

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: Sun Jul 19 22:30:03 PDT 2026