National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS66 KMTR 182124
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
224 PM PDT Thu Apr 18 2024

...New SYNOPSIS, SHORT TERM, LONG TERM...

.SYNOPSIS...
Issued at 142 PM PDT Thu Apr 18 2024

A touch cooler Friday as a weak system moves through. Chance for
light drizzle for coastal areas the next couple of days. Temperatures
rebound late weekend and early next week. Chance for light rain
enters the forecast mid next week.


&&

.SHORT TERM...
(This evening through Saturday)
Issued at 142 PM PDT Thu Apr 18 2024

Increased cloud cover today along coastal areas south of SF as the
marine layer deepens ahead of the approaching weak trough. Still
looking like a progressive, open wave, this system will scoot
through rather quickly Friday, bringing additional cloud cover and
a slight chance for drizzle along coastal locations and higher
elevations of the East Bay Friday and Saturday mornings. The other
impact from this system will be the breezy NW winds that develop
along the coast as the system departs. Generally looking at gusts
of 25-30 mph along the immediate coast Saturday afternoon into
Sunday afternoon.

&&

.LONG TERM...
(Saturday night through next Wednesday)
Issued at 142 PM PDT Thu Apr 18 2024

By Sunday, ridging dominates the pattern once again with temps
warming back into near 80 for inland areas and 60s to near 70
along the coast. Similar picture into Monday as well. Tuesday
brings some changes. Ensemble guidance continues to advertise
anomalous troughing over the EPac/West Coast during the mid-to-
late next week period, hinting at a pattern that promotes above
average precip and below average temperatures. Average precip for
the second half of April for our region is roughly a half inch,
give or take a few tenths depending on if you`re coastal or
inland. What we`re expecting next week is generally on the order
of a trace to a few tenths here and there. Longer terms guidance
does show the pattern continuing into next weekend, where there
could be additional light rainfall, bringing us into that
ballpark of slightly above normal. The main caveat with this
forecast is that while there is moderate to high confidence in the
overall pattern, the confidence in widespread measurable rainfall
is low. In fact, in a grouping of 100 different models, roughly 24
of them advertise any measurable precip for us at all through next
weekend. The answer to the question of next week being widespread
light rain or just some increased cloudiness and drizzle will
need further refinement in future forecasts. For now, plan on the
latter half of next week being cool and damp.

&&

.AVIATION...
(18Z TAFS)
Issued at 1034 AM PDT Thu Apr 18 2024

VFR to continue through the evening with MVFR-IFR returning
overnight for most stations. HREF indicates stratus will return
along the coast and move inland around 08-12Z with a slightly
earlier return (03-06Z) along the Central Coast. Low to moderate
confidence that fog will develop overnight at STS, SNS, and MRY
with guidance indicating moderate potential for LIFR conditions
at STS and SNS. For most stations, stratus looks to dissipate by
mid-morning but at a few stations (STS, APC, SNS, MRY)
dissipation looks to occur by late morning shortly after this TAF
period ends. Light to moderate SW to W winds will continue through
the day with winds becoming light and variable overnight.

Vicinity of SFO...VFR with MVFR returning overnight. Stratus will
return during the early morning with MVFR CIGs and only minor
impacts to visibility anticipated. Low confidence that fog will
develop at SFO but if lower CIGs do develop 12-16Z looks to be the
best time frame. Stratus is expected to clear out by mid-morning
between 17-18Z. Moderate W winds persist through the afternoon with
light, variable winds returning overnight. Moderate W winds return
by mid to late morning tomorrow.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR transitioning to MVFR-IFR overnight.
Guidance indicates MVFR and IFR CIGs will develop overnight with
increasing potential for LIFR CIGs to develop, particularly at SNS.
Low to moderate confidence that fog will develop at SNS and MRY. If
fog does develop, LIFR CIGs and significantly reduced visibilities
are likely. Confidence is higher for fog development at SNS than MRY
with guidance indicating high RH values and weak winds between 06-
16Z. Moderate W-NW winds during the day with light, variable winds
returning overnight.

&&

.MARINE...
(Today through Tuesday)
Issued at 1034 AM PDT Thu Apr 18 2024

Expect light to moderate winds into the weekend before breezy to
gusty northerly winds arrive Saturday afternoon. Wave heights will
start to build heading into the late weekend to early next week.
Another moderate period northwest swell arrives over the weekend
as well as another light, longer period (18 seconds) southerly
swell.

&&

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

$$

SHORT TERM...Behringer
LONG TERM....Behringer
AVIATION...Kennedy
MARINE...Kennedy

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/nwsbayarea
www.twitter.com/nwsbayarea
www.youtube.com/nwsbayarea