463
FXUS66 KMTR 181812
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1112 AM PDT Wed Sep 18 2024

...New AVIATION...

.SYNOPSIS...
Issued at 1252 AM PDT Wed Sep 18 2024

Chance of scattered showers today, tapering off from north to
south gradually through Thursday morning. A warming trend is on
tap for the rest of the week with seasonal normal temps expected
by the weekend.

&&

.UPDATE...
Issued at 924 AM PDT Wed Sep 18 2024

Precipitation over the region has been mainly across the northern
Santa Cruz Mountains and into the East Bay with reports up to 0.06"
at Rocky Ridge (RGEC1). However, expecting rain to increase over the
North Bay in the next couple of hours as a rain band approaches the
region. As the low pressure center remains offshore, rain is
expected to be less widespread as once thought with the region
picking up around a trace to a few hundredths of an inch through the
afternoon and evening. That said, the forecast remains on track with
no updates anticipated at this time.

&&

.SHORT TERM...
(Today and Thursday)
Issued at 1252 AM PDT Wed Sep 18 2024

The next system is currently moving in, made noticeable by the
influx of higher cloud cover through the evening. As of about
midnight, the surface low was located just off the coast of
Oregon. The low will move southward through this morning, bringing
light rain chances to the Bay Area by mid-to-late morning. There
is a slight chance (~15%) of thunder during this time period,
mainly in the North Bay. As the low moves through, moisture
wrapping around the back side will affect areas south of the Bay
Area, including the Central Coast, by the middle of Thursday
morning. There is also a slight chance of thunder here during this
time. Though a small chance, there could be some terrain
enhancement over the Santa Lucia, resulting in isolated, brief
heavier rain than what will be seen elsewhere. Shower activity
ends gradually Thursday evening as the low moves inland.

&&

.LONG TERM...
(Friday through Tuesday)
Issued at 1252 AM PDT Wed Sep 18 2024

A warming trend will kick off Friday into the weekend as the upper
low exits and confidence grows in an a broad upper level ridge
situated off the west coast. Temperatures through the weekend are
expected to be near seasonal normals. Warming continues into early
next week where we will begin to see slightly above normal
temperatures.

&&

.AVIATION...
(18Z TAFS)
Issued at 1112 AM PDT Wed Sep 18 2024

Approaching showers have slowed down slightly but are expected to
reach the Bay Area by late this morning and continue into the
afternoon. Currently a mix of mid-level clouds and MVFR CIGs with
VFR conditions to return during the afternoon/evening. Any showers
that do directly impact airports may result in temporary decreased
visibility and lowered ceilings. Confidence remains low on inclusion
of thunderstorms in TAFs. For all sites except STS, there is a less
then 8% chance of thunderstorms. For STS, thunderstorm chances reach
10-12% beginning early this afternoon through the evening. Shower
chances decrease at all airports except MRY and SNS beginning this
evening with MVFR CIGs expected to return overnight. Light to
moderate southwesterly winds continue into the afternoon before
becoming more northwesterly after cold frontal passage later this
afternoon.

Vicinity of SFO...Scattered showers will arrive within the next few
hours. Any precipitation that reaches the surface will generally be
light but if a stronger shower moves directly over the airport
visibilities may temporarily decrease. A low chance (~5%) of
thunderstorms continues for SFO through this afternoon. Confidence
is too low to include in TAFs but will continue to monitor as
showers start to approach the SF Peninsula. Moderate west to
northwest winds continue with winds weakening slightly overnight.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Scattered showers are expected to move
through the Central Coast through late this evening. Low chance of
thunderstorms (~4-5%) continues through this evening but confidence
remains too low to include thunderstorms in TAFs. MVFR to IFR CIGs
are expected to return later this evening with an early return around
02-03Z. Low to moderate confidence on timing of transition from MVFR
to IFR CIGs overnight. Moderate northwesterly winds are expected
during the day with lighter, variable winds overnight.

&&

.MARINE...
(Today through Monday)
Issued at 924 AM PDT Wed Sep 18 2024

Northwesterly winds will become gusty across the outer waters by
late Wednesday. Seas will be moderate, building to become rough in
the outer waters by Thursday. Unsettled conditions will continue
over the outer waters through the weekend. Showers continue over
the coastal waters through this afternoon. There is up to a 12%
chance for thunderstorms in the mid morning which could produce
lightning, locally heavy rainfall, locally gusty winds.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM Thursday to 3 AM PDT Friday for
     Pt Arena to Pt Reyes 10-60 NM.

&&

$$

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

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