Technical NOAA Weather Discussion

FXUS66 KMTR 192334
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
434 PM PDT Sun Apr 19 2026

...New AVIATION, MARINE...

.KEY MESSAGES...
Updated at 935 PM PDT Sat Apr 18 2026

 - Seasonally warm temperatures Sunday

 - Cooler temperatures, beneficial rainfall, and isolated
   thunderstorms expected Monday through Wednesday

&&

.SHORT TERM...
Issued at 235 PM PDT Sun Apr 19 2026 
(This evening through Monday)

Pleasant end to the weekend for the Bay Area and Central Coast 
weather wise with filtered sunshine and seasonably mild 
temperatures. Max temps today will peak in the 60s to mid 70s 
with a few interior spots making a run at 80 plus. 

Stepping back and taking look at the bigger picture reveals a 
system lurking off the coast. In fact, pretty impressive looking
visible satellite imagery this afternoon. A discernible
circulation is spinning off the PacNW with a band of clouds
wrapping around the system and stretching along the West Coast.
The circulation is an anomalously deep upper low. At the surface 
is a double barrel low pressure system with a marked frontal 
structure. The surface low and front will begin to inch its way 
eastward Sunday evening and Sunday night. The advancing cold front
will bring increasing clouds and a few scout showers to the 
northern coastal waters and far northern Sonoma county. Not 
expecting much in the way of accumulating precip with these 
leading showers through Sunday night. 

More widespread precip is expected on Monday as the highly
amplified upper jet begins to phase off the CA coast. Light to 
moderate rain will begin across the North Bay toward the end of 
the AM commute. Rain will spread S and E through the day with the 
passage of the cold front. Expect the evening commute to be pretty
messy with wet roads.

In addition to the rain on Monday, southerly flow will ramp 
thanks to a tightening surface gradient. Winds are initially
strongest over the waters before hitting the coast and inland
areas by the afternoon. Not strong enough for a wind advisory, but
general gusts in the 30-40 mph range seems reasonable. Given the
southerly flow, initial rain chances for some areas will be eaten
thanks to downslope flow and rain shadowing. 

As for temperatures, despite a pattern change temperatures will 
be mild since the region will be in a warmer sector until fropa. 
Given the solid S flow think there could be some enhanced 
downslope warming - thinking Monterey. 

&&

.LONG TERM...
Issued at 238 PM PDT Sun Apr 19 2026 
(Monday night through next Saturday)

Monday looks wet, but Tuesday may end up being a little more
dynamic thanks to convection. A few things we'll be watching for
Tuesday: cold pool aloft behind the front destabilizing the 
atmosphere, approaching upper low, position of left exit of jet 
aloft, and wind profiles relating to low level shear. While those
pieces varying from model to model, enough of a signal is present
to justify having thunderstorms in the forecast for Tuesday. 
Putting things into better context, the ECMWF Extreme Forecast 
Index has strong signal for CAPE over the coastal waters giving 
more confidence to thunderstorms. SPC Day 3 outlook does have the 
entire region in a general mention of thunderstorms. 

Monday's rain and Tuesday additional shower activity should be
mostly beneficial rain, but given the convective nature local 
ponding/minor flooding is possible. Lingering showers will 
continue into Wednesday afternoon thanks to a trailing shortwave 
behind the departing upper level low/trough.

Warmer and drier conditions there after.

&&

.AVIATION...
(00Z TAFS)
Issued at 425 PM PDT Sun Apr 19 2026

A slow moving cold front approaching the coast will dominate the
weather through this TAF period and beyond. High cloud coverage
will increase overnight as winds trend southerly. Rain should
reach the North Bay late Monday morning and move south through the
day. This rain will be preceded by high MVFR or VFR clouds for 
all terminals.

Vicinity of SFO...There is very little chance for low ceilings 
before 12Z when the more direct impacts from the approaching cold 
front start to move over the terminal. Rain should reach the 
terminal sometime between 18Z and 00Z before the intensity 
increases Monday night.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...The front is creeping very slowly and 
impacts will take longer to reach the southern terminals. The best
chance for rain onset is Monday afternoon/evening. 

&&

.MARINE...
(Tonight through next Friday)
Issued at 425 PM PDT Sun Apr 19 2026

Calm conditions continue into the night. Breezy and gusty winds
build ahead of a slow moving cold front that arrives on Monday.
Rain will accompany the cold front starting Monday and lingering
into early Wednesday. Chances of thunderstorms will move through
the waters for much of Tuesday. Dry weather returns late in the
week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 9 AM to 9 PM PDT Monday for SF Bay N 
     of Bay Bridge.

     Small Craft Advisory from 9 AM Monday to 3 AM PDT Tuesday for 
     Mry Bay.

     Small Craft Advisory from 3 AM to 9 PM PDT Monday for Pigeon Pt 
     to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena 
     to Pt Reyes 10-60 NM-Pt Reyes to Pigeon Pt 0-10 nm.

     Small Craft Advisory from 3 AM Monday to 3 AM PDT Tuesday for 
     Pigeon Pt to Pt Pinos 0-10 nm-Pt Pinos to Pt Piedras 
     Blancas 0-10 nm.

&&

$$

SHORT TERM...MM
LONG TERM....MM
AVIATION...Flynn
MARINE...Murdock

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Prepared by Boulder-Creek.com Weather at: Sun Apr 19 20:30:03 PDT 2026
From the National Weather Service