FXUS66 KMTR 192056
AFDMTR

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

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

.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...
(18Z TAFS)
Issued at 1141 AM PDT Sun Jul 19 2026

Flight categories continue to improve and over the next 2-4 hours
VFR is anticipated at OAK, HAF, and MRY. There is high confidence
that MVFR/IFR stratus and BR will make a return tonight into 
Monday morning. However, the marine layer is projected to compress
and this lowers confidence in the specifics. There's medium 
confidence that LIFR will transpire at STS and HAF due to a 
combination of stratus and BR. While some hi-resolution guidance 
does suggest a threat for visibility under 1/2 mile, confidence 
remains too low to include at this time. The compressed marine 
layer will limit the duration of stratus at SJC and LVK is 
forecast to remain VFR. There is a non-zero potential for elevated
showers with largely virga/turbulence, with the greatest chance 
(~10%) at HAF, STS, and APC. While the current TAF set omits VCSH,
inclusion may be warranted in future forecasts as confidence 
increases. For now, mid- level clouds between FL100-FL150 will 
stream in overhead. 

Vicinity of SFO...VFR has returned with diurnal WNW'ly winds in
progress. VFR is expected through 07Z Mon, though there's a
potential that MVFR stratus may return sooner than advertised. If
this transpires, impacts to the evening push should be
anticipated. The compressed marine layer lowers forecast 
confidence in IFR at SFO, but nearly half of short-range hi-res 
guidance advertises intermittent cigs below FL010 around sunrise 
Monday. VFR should make a swift return mid-morning Monday. The 
potential for elevated showers INVOF SFO is low with the greater 
chance to the north and west of the terminal. 

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR anticipated shortly at MRY.
Otherwise, diurnal breezes and VFR this afternoon. Stratus 
returns near/just after 00Z Mon and will initially be MVFR. 
Roughly 2-3 hours thereafter, ceilings will lower into the IFR 
category. The compressed marine layer does support the 
introduction of IFR visibility and LIFR ceilings at MRY around 
9Z. This potential isn't quite as high at SNS, but trends will be 
monitored. A return to VFR is more probable after the end of the 
current valid TAF period, unless the inland intrusion of stratus 
is less than anticipated.

&&

.MARINE...
(Today through Friday)
Issued at 1141 AM PDT Sun Jul 19 2026

Gentle to moderate northwesterly breezes will persist through the
upcoming workweek with slight to moderate seas. As tropical
cyclone activity continues across the eastern Pacific, long period
southerly swell is forecast. While heights for the southerly
swell are largely anticipated to remain in the slight category,
mixed seas may result in hazardous boating conditions through the
week. In addition, there are non-zero chances for high based
showers which could result in pockets of gusty outflow winds and
subsequent steep seas 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...Bain
MARINE...Bain

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Prepared by Boulder-Creek.com Weather at: Sun Jul 19 16:30:03 PDT 2026