National Weather Service United States Department of Commerce

Excessive Rainfall and Tropical Storm in the South; Severe Thunderstorms in the Midwest

Excessive rainfall may produce considerable, potentially life-threatening, flooding across the lower Mississippi River Valley and central Great Lakes region through tonight. Tropical Storm Arthur will move northeastward along the Texas coast today and then move inland over southwestern Louisiana by tonight. An outbreak of severe thunderstorms is expected across portions of Illinois and Indiana. Read More >

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234
FXUS66 KMTR 172317
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
417 PM PDT Wed Jun 17 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 156 PM PDT Wed Jun 17 2026

- Minor coastal flooding due to higher than normal high tides
anticipated across low-lying coastal areas.

- Hazardous beach conditions as well with increased risk of
sneaker waves and strong rip currents.

- Minor HeatRisk through the end of the week with temperatures
cooling to below normal.

&&

.SHORT TERM...
Issued at 156 PM PDT Wed Jun 17 2026
(This evening through Thursday night)

The marine layer, ~1500ft, continues to retreat back towards the
coast, having lingered a bit longer than expected for the San
Francisco Bay and into the northern interior valley, bringing
slightly cooler high temps for today. Expect the marine layer to
push back onshore tonight. Have included drizzle along the coast
as the marine layer slightly deepens as the ridge breaks down as
troughing pushes east towards the coast. Patchy fog for interior
valleys possible as well. The slight cooling trend will continue
into Thursday, especially for interior locations, as a result of
the troughing and slightly stronger onshore flow, with afternoon
highs in the 60s along the coast to mid 70s to 80s for interior
locales. The marine layer builds to ~2000kt and expands further
inland for tomorrow night, with more fog and drizzle expected.

Tidal flooding continues across low-lying coastal and Bayshore
areas through Thursday morning as high astronomical tides combine
with surge effects from wind, swell, and thermal expansion to
bring us the highest tides of the summer season. High tide is
expected to be 1.2 ft above normal (7.1 ft MLLW) at 1:51 AM on
Thursday. In addition, the long-period southerly swell continues,
which increases the risk for sneaker waves and strong rip
currents, with a Beach Hazards Statement out through late Friday
night. See the BEACHES section for more information, but the main
takeaway is to never turn your back to the ocean!

&&

.LONG TERM...
Issued at 156 PM PDT Wed Jun 17 2026
(Friday through Wednesday)

The trough will begin to move onshore on Friday and pass over the
region through the weekend, with the cooling trend continuing.
Shower and thunderstorm potential associated with the trough will
stay primarily over the higher terrain to the north and east of
the area as a deep marine layer greatly inhibits any thunderstorm
potential. However, there will be enough elevated instability for
cumulus development and around a 5% chance of thunderstorms
across far northern Napa and Sonoma counties Thursday night and
Friday with lower chances to the south.

The marine layer will likely deepen as the trough passes through,
with the cooling trend continuing through Saturday. Afternoon
highs temps will only reach the 70s to low 80s for interior
location and upper 50s to mid 60s along the coast. The onshore
flow will continue with breezy afternoon winds. Coastal areas will
could continue to see drizzle.

By Sunday, the trough is expected to weaken as model guidance is
suggesting a ridge building across the western US into next week.
This will bring a warming trend, beginning Sunday into next week,
with a return of some 90s and moderate HeatRisk concerns by
midweek for some interior areas.

&&

.AVIATION...
(00Z TAFS)
Issued at 417 PM PDT Wed Jun 17 2026

MVFR-IFR stratus is confined to the immediate coast with breezy
onshore winds with a southerly component and strong gusts through
the evening hours. Generally MVFR with some borderline IFR stratus
will return to the North Bay, central SF Bay, and Monterey Bay
terminals overnight with low to moderate confidence in stratus
impacts at LVK and SJC, where the marine layer is thick enough to
bring stratus into both terminals but the lower level southwest flow
may inhibit stratus flow into those areas. May need to monitor
conditions through the night. Stratus should retreat to the coastal
areas through Thursday morning and the breezy and gusty southwest
pattern winds should resume in the afternoon.

Vicinity of SFO... VFR conditions at present with breezy and
southwest winds in place through the evening. MVFR-IFR stratus moves
in overnight with impacts expected by 07-09Z. Stratus will dissipate
through Thursday morning with breezy southwest winds returning to
the terminal in the afternoon. Stratus will return to the terminal
area late Thursday night to early Friday morning, right at or after
the end of the TAF period.

SFO Bridge Approach... Lower confidence of stratus impacts tonight
with the large scale southwest flow, as high resolution models tend
to keep the stratus deck away from the approach path. Otherwise
similar to SFO.

Vicinity of OAK and SJC... VFR with breezy northwest winds at both
terminals through the evening hours. At OAK, MVFR-IFR stratus should
flow into the terminal area this evening with moderate confidence of
impact timing, as high resolution models generally aim for the 02-
05Z timeframe. At SJC, there is much less confidence in the stratus
forecast. High resolution model output keeps the terminal area
clear, but places scattered stratus in the vicinity and particularly
to the north of the terminal. This may need to be watched closely
during the night. Stratus will dissipate through the course of
Thursday morning, with breezy and possibly gusty winds developing
through the afternoon. Winds remain northwesterly at OAK but
moderate confidence for southwest flow at SJC.

Monterey Bay Terminals... VFR conditions at the moment with breezy
southwest winds at MRY and northwest winds with strong gusts at SNS
continuing into the evening hours. MVFR-IFR stratus will come over
both terminals within the next couple of hours and persist through
the night. Stratus will retreat to the immediate coast Thursday
morning with winds during the afternoon exhibiting a similar pattern
to today`s winds.

&&

.MARINE...
(Tonight through next Monday)
Issued at 417 PM PDT Wed Jun 17 2026

Moderate to fresh west/southwest winds in the bays will diminish
around sunset this evening. Winds increase again for the next
couple afternoons and evenings with strong breezes anticipated,
leading to hazardous conditions for small crafts. Light to
moderate seas with southwesterly swell will continue into the
weekend. Moderate west/southwest winds and moderate seas will
prevail over the open ocean into the weekend.

&&

.BEACHES...
Issued at 156 PM PDT Wed Jun 17 2026

Long period southerly swell at around 15 to 17 seconds will persist
through early Saturday as energetic storms in the Southern
Hemisphere continue to affect the California coast, especially for
south and southwest facing beaches. Hazardous beach conditions
are advertised, specifically for moderate to steeply sloped
beaches along the Pacific Coast of the North Bay, San Mateo, Santa
Cruz counties. A Beach Hazards Statement for Pacific Coast
beaches continues through late Friday night. Be sure to check
beach conditions before you head out. Sneaker waves will run up
the beach much farther than other waves, potentially catching
beachgoers by surprise and resulting in people being swept into
the water. Rip currents are strong enough to pull the strongest
swimmers away from shore. Swim near a lifeguard if possible. Stay
back from the beach, and away from jetties, piers, beachside
rocks, and other infrastructure near the water. Never turn your
back to the ocean!

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through late Friday night for CAZ006-505-
509-529-530.

Coastal Flood Advisory until 5 AM PDT Thursday for CAZ006-506-
508.

PZ...Small Craft Advisory from 3 PM to 9 PM PDT Thursday for Mry Bay-
SF Bay N of Bay Bridge.

&&

$$

SHORT TERM...Slagle
LONG TERM....Slagle
AVIATION...DialH
MARINE...Berislavich

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