659
FXUS66 KMTR 200354
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
854 PM PDT Sat Apr 19 2025

...New UPDATE, MARINE...

.SYNOPSIS...
Issued at 127 PM PDT Sat Apr 19 2025

Slight warming trend expected Monday and Tuesday before cooler,
cloudier conditions return Wednesday into the weekend. Continuing
to monitor a slight chance for light rain Friday into the weekend.

&&

.UPDATE...
Issued at 846 PM PDT Sat Apr 19 2025

The forecast remains on track this evening with low stratus
confined mostly to the coastline, with the exception of Half Moon
Bay and Monterey Bay where local small scale circulations are
feeding a steady fetch of low level marine layer stratus farther
inland. Those portions of southern Sonoma County, Santa Cruz
County and northern Monterey County can expect the stratus to
linger through the night into Sunday afternoon.

&&

.SHORT TERM...
(This evening through Sunday)
Issued at 127 PM PDT Sat Apr 19 2025

Stratus is dissipating across the interior but persists along the
coastline. The exception to this is interior Sonoma County where a
circulation just offshore continues to feed stratus into the Sonoma
Valley. Nudged high temperatures along the coast down by 2-3 degrees
to account for continued stratus coverage along the coast with highs
forecast to reach the upper 50s to low 60s. Across the interior,
clearing skies will allow for increased radiational warming with
highs to reach the upper 60s to mid 70s. Some uncertainty remains
about high temperatures across the Sonoma Valley, if stratus
coverage is able to dissipate within the next few hours then high
temperatures are likely to reach the low 70s. If stratus coverage
persists into the mid to late afternoon, high temperatures will
struggle to reach the upper 60s. We`ll keep an eye on satellite and
evaluate if any changes need to be made for today`s forecast across
the North Bay. Light, onshore winds will persist through the
remainder of the weekend with locally breezier conditions across the
elevated terrain. A weak shortwave trough will move through the
region this evening into Sunday. This disturbance will allow the
marine layer to deepen to around 2000ft and bring widespread
overcast conditions to the Bay Area and Central Coast. High
temperatures on Sunday are forecast to be in the low to mid 70s
across the interior and upper 50s to mid 60s along the coastline.
The main question for tomorrow`s forecast is how long stratus
coverage will persist and what impact that will have on the high
temperatures. We may expect to see a similar setup to today, where
areas that have prolonged stratus coverage may struggle to reach
their forecast highs vs areas that clear faster will reach their
forecast highs more easily.

&&

.LONG TERM...
(Sunday night through next Friday)
Issued at 127 PM PDT Sat Apr 19 2025

By Sunday evening, the weak upper level disturbance will have exited
the region with high pressure and zonal upper level flow replacing
it. High resolution guidance shows the marine layer compressing to
around 500 ft starting Sunday night and remaining compressed through
Tuesday. The combination of a compressed marine layer, zonal flow,
and high pressure will result in rising temperatures Monday and
Tuesday. Temperatures across the interior will be about 5 to 10
degrees above normal in the mid to upper 70s with a few areas
possibly reaching the low 80s. Along the coast temperatures will be
cooler, more seasonal, with highs in the low to mid 60s expected.
Minor HeatRisk persists Monday and Tuesday for portions of the Bay
Area and Central Coast but this will primarily only impact
individuals who are incredibly sensitive to heat.

The pattern shifts Wednesday with interior temperatures going from
above normal to below normal as zonal upper level flow gives way to
upper level troughing. A weaker upper level trough will arrive
Wednesday, giving way to weak ridging on Thursday, before a deeper
upper level trough arrives Friday. This second trough (Friday into
the weekend) will be associated with a surface low pressure system
and a cold front moving through the region. Temperatures will cool
to the mid to upper 60s across the interior and to the upper 50s to
low 60s along the coast starting Wednesday. Cooler temperatures will
persist through the end of the forecast period with CPC guidance
highlighting below normal temperatures continuing through the end of
April. We are still monitoring potential for light rain towards the
end of the forecast period (Friday into the weekend) with ensemble
guidance indicating some potential for light rain. However, there is
still a fair amount of uncertainty regarding how deep upper level
troughing will be and how far south rain will spread. For example,
the previous forecast update showed more widespread light rain
across the Bay Area and Central Coast while this afternoon`s limited
it to the North Bay. It is likely we will see some light rain from
this system but it is still too far out for exact locations and
forecast amounts. Initial NBM guidance suggests some potential for
breezier conditions next weekend as this system moves through the
region. Guidance is likely to continue fluctuating in the short term
with forecast confidence increasing as we get closer to the end of
next week.

&&

.AVIATION...
(00Z TAFS)
Issued at 452 PM PDT Sat Apr 19 2025

Mostly VFR but there are several terminals that are still
experiencing low ceilings, especially along the coast. Therefore,
expect MVFR ceilings to retreat back to the coast for couple of
hours after 00Z. After 02-03Z, expect another push of MVFR/IFR
conditions early this evening and lasting into the morning. VFR is
expected to return after 18Z for most terminals as diurnal
warming and mixing goes into affect, with a chance it may linger
into 19- 20Z. Winds will diminish overnight to light to moderate
and will rebuild to moderate to breezy by Sunday afternoon.

Vicinity of SFO...VFR currently but a FEW low clouds linger near the
terminals. Breezy onshore winds will diminish tonight but will
rebuild by Sunday afternoon. MVFR conditions will return this
evening and last until 18Z. There is a chance for later clearing
near 19-20Z, but confidence is low.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...MVFR conditions but satellite shows
clearing will occur soon, but MVFR/IFR/LIFR is expect to have a
early return near 02-03Z and last until 18-19Z.

&&

.MARINE...
(Tonight through next Friday)
Issued at 846 PM PDT Sat Apr 19 2025

A week cold front will begin to move south through our area
tonight and Sunday. Expect breezy to gusty north/northwest winds
and a building north swell. The gusty northerly winds will persist
into next week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM Sunday to 3 AM PDT Monday for Pt
     Arena to Pt Reyes 0-10 nm.

     Small Craft Advisory until 3 PM PDT Tuesday for Pt Arena to Pt
     Reyes 10-60 NM.

     Small Craft Advisory from 9 AM Sunday to 3 PM PDT Tuesday for
     Pigeon Pt to Pt Pinos 10-60 NM.

&&

$$

SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...SO
MARINE...JM

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