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Severe Thunderstorms; Excessive Rainfall; Dangerous Heat; Air Quality Concerns and the Tropics

Wildfire smoke will push into the Midwest, worsening air quality. A frontal system brings severe storms from the Northern Plains to the Mid‑Atlantic the next few days. Heavy Gulf Coast rain is possible as Tropical Depression Two has formed, while monsoonal storms persist in the Southwest with heavy rainfall. Hazardous heat expands from the Plains into the Lower Mississippi Valley. Read More >

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438
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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