620
FXUS66 KMTR 211940
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1240 PM PDT Tue May 21 2024

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

.SYNOPSIS...
Issued at 1237 PM PDT Tue May 21 2024

Summer-like pattern to persist through Thursday. Temperatures are
forecast to dip below seasonal averages by the upcoming weekend
as an upper level trough impacts the region.

&&

.SHORT TERM...
(This evening through Wednesday)
Issued at 1237 PM PDT Tue May 21 2024

The broad tilted upper level troughing pattern over California has
brought some weak offshore winds over interior areas, causing some
warmer temperatures and drier conditions. The offshore flow will
help inhibit some of the marine layer from reaching inland tonight
into Wednesday morning allowing for another blue sky morning for
interior regions. On the other hand, the weak onshore flow along the
coast will bring some low clouds along the coastal areas, especially
near Monterey Bay and Salinas Valley tonight. Models show interior
regions will be on the drier side this evening with minimum relative
humidity values between 14-30%.

Overnight temperatures are relatively the same as last night with
minimums in the mid to upper 40`s to low to mid 50`s. Some isolated
areas will see a slight increase 2-3 degrees higher. Temperatures
will start to trend cooler on Wednesday, but still will be
relatively warmer than usual with inland max temperatures in the low
80s to high 70s, as coastal areas will see temperatures in the upper
50s to 60s. The onshore flow along the coast will increase on
Wednesday, which will help increase some relative humidity values
between 20-55%.

&&

.LONG TERM...
(Wednesday night through next Monday)
Issued at 1237 PM PDT Tue May 21 2024

The low pressure system that sits in the northwest, will drop south
a bit on Thursday and will move across the Pacific northwest over
the weekend, which will bring stronger onshore flow and cooler
temperatures. Thursday will start to see max temperatures in the mid
70s inland and upper 50s to 60s along the coast. Friday through the
weekend, max temperatures are expected to drop between 5 to 7
degrees below average over the weekend with mid 50s to low 60s
coastline and upper 60s to low 70s inland. With the stronger onshore
flow, expect the gloomy mornings pattern to continue along the
coast, with slow clearing in the mornings. Ensemble models show
no impactful precipitation associated with this trough as it
moves through our area this weekend, but if precipitation does
occur this weekend, expect the best chance to occur near the
coast. On Sunday into Monday, a weak ridging will develop over our
area bringing back some slightly warmer temperatures.

&&

.AVIATION...
(18Z TAFS)
Issued at 1020 AM PDT Tue May 21 2024

Currently VFR at all terminals with stratus hugging the coastline
from the San Francisco Peninsula down to Point Conception. Moderate-
high confidence of VFR through the TAF period at all terminals with
the exception of the Monterey Bay terminals of MRY and SNS.

Vicinity of SFO...Currently VFR with offshore flow. VFR through the
TAF period. Winds will transition to become breezy out of the west
by this afternoon with gusts up to 25 knots to be expected.
Confidence is moderate that the terminal will evade a ceiling;
however, there will likely be low clouds in the FL010-FL030 range
between 10Z and 16Z. Winds will become breezy out of the west again
tomorrow afternoon with gusts up to 25 knots to be expected.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Currently VFR with westerly flow at MRY
and VFR with northerly flow at SNS. Moderate-high confidence that
MVFR stratus will return to both terminals overnight, with lower
confidence on if ceilings will dip into IFR territory. Winds will
remain breezy through the TAF period and out of the west/southwest
for MRY and out of the west/northwest for SNS.

&&

.MARINE...
(Today through Sunday)
Issued at 1020 AM PDT Tue May 21 2024

Building surface high pressure over the Eastern Pacific Ocean
will continue to allow for strong northwesterly winds to prevail
through Thursday, with gale force gusts across the outer coastal
waters. Expect hazardous conditions and steeper wind waves during
the week. Winds diminish heading into the weekend as surface high
pressure over the Eastern Pacific Ocean weakens and retrogrades
to the west.

&&

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

     Small Craft Advisory until 3 PM PDT Wednesday for Pt Reyes to
     Pigeon Pt 0-10 nm.

     Small Craft Advisory until 9 PM PDT this evening for Pigeon Pt
     to Pt Pinos 0-10 nm.

     Small Craft Advisory from 9 AM to 3 PM PDT Wednesday for Pigeon
     Pt to Pt Pinos 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10
     nm.

     Gale Warning until 3 PM PDT Wednesday for Pt Arena to Pt Reyes
     10-60 NM.

     Gale Warning until 3 AM PDT Wednesday for Pigeon Pt to Pt Pinos
     10-60 NM.

&&

$$

SHORT TERM...SO
LONG TERM....SO
AVIATION...Sarment
MARINE...Sarment

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