436
FXUS66 KMTR 301920
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1220 PM PDT Tue Apr 30 2024

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 133 AM PDT Tue Apr 30 2024

High pressure brings quiet weather and slowly warming temperatures
this week. Breezy onshore winds will keep temperatures along the
coast cooler however. Cooler and more unsettled conditions return
this weekend into next week with light rain chances in the forecast.

&&

.UPDATE...
Issued at 854 AM PDT Tue Apr 30 2024

Low clouds continue to dissipate across the Santa Clara Valley and
the Santa Cruz Mountains this morning while they are hanging around
the Monterey Bay region. However, conditions will continue to
improve throughout the morning with mostly sunny conditions this
afternoon. Breezy northwest winds will also prevail and strengthen
this afternoon with gale force gusts out over the ocean. No changes
anticipated to the ongoing forecast.

&&

.SHORT TERM...
(Today and tonight)
Issued at 203 AM PDT Tue Apr 30 2024

Dry conditions prevailing with high pressure from the offshore
waters to far northern California and the Pacific Northwest.
Gusty northwest winds continue over the coastal waters. Forecast
highs today 60s near the coast and bays to the 70s inland.

&&

.LONG TERM...
(Wednesday through Monday)
Issued at 203 AM PDT Tue Apr 30 2024

Dry conditions prevailing through mid-week. A slowly retrograding
long wave trough along the West Coast varies in strength late
week and early next week. There is a large difference between
recent GFS (wet) and ECMWF (not nearly as wet as the GFS) in
calculating the trajectory/progression of a low pressure system
moving through the long wave trough, now well within 120 hours (5
days) forecast. QPF differences are showing up in the GEFS and EPS
as well, though recent EPS have increased a little. As of current,
it remains a low confidence forecast from a global model forecast
perspective. Given the model forecast trajectory of the low pressure
system is from near the Bering Sea/Aleutians southeastward across
the Pacific (and surface high pressure over the Pacific retrogrades)
where below normal sea surface temperatures exist including a
negative phase Pacific Decadal Oscillation (PDO) i.e. the potential
forward slowing due to local surface heating is reduced therefore
the quicker arriving QPF in the GFS solution may not be that far
off if development much closer to our forecast area verifies. The
northern hemispheric pattern remains active with the current number
of long wave troughs reflecting a winter-like circulation.

Stay tuned to latest forecast updates, as currently advertised
the official forecast shows potential for showery, cool weather
this weekend. Planning travel to the mountains? This pattern has
potential for snow accumulations, it`s a good idea to monitor the
latest forecasts. Per 30 year climatology we are of course past
peak cool season rainfall, however it can still rain in May in the
Bay Area and north Central Coast. Recalling a Lead Forecaster here
years ago mentioned it`s always a good idea to carry chains in case
needed (for Sierra Nevada travel) through Memorial Day.

July climatologically is our driest time of year since by then the
jet stream has reliably weakened and returned northward and high
pressure often sets up.

&&

.AVIATION...
(18Z TAFS)
Issued at 1220 PM PDT Tue Apr 30 2024

VFR conditions prevail through the TAF period. However, strong and
gusty winds will be the main concern through the late evening today.
Winds increase out of the W/NW to become sustained generally
around 15-20 knots into the afternoon today, with gusts in the
25-30 kt range. The one exception to prevailing gusty conditions
this afternoon will likely be Monterey Bay terminals, though they
will still see winds nearing 15 kts. One thing to keep an eye on
will be whether winds at KSFO strengthen above the forecast 30 kt
gusts. Will expand more on this in their discussion section.

Into the late night tonight, winds slowly ease near the surface, but
in the mid levels (1500+ feet), winds turn more northerly and
increase to around 25-30 kts on average, with select terminals
seeing stronger winds. This will introduce directional and speed
shear for most terminals tonight, especially the North Bay. It is
not until the mid to late morning of Wednesday that wind shear
diminishes.

Vicinity of SFO...VFR through the TAF period, with the terminal
seeing strong and gusty winds out of the W/NW. Current thought is
that wind gusts will stay contained to around 30 kt this afternoon
and not exceed or reach AWW criteria (35 kt). As it currently
stands, high resolution models have the mean (50th percentile) wind
gusts this afternoon at KSFO at 25 kts, with the higher end (90th
percentile) only reaching 28 kts around the time for strongest winds
near 01Z. However, current SFO-ACV gradient is stronger now than at
this same time yesterday. Therefore, moderate confidence in wind
gusts not exceeding 30 kt at KSFO this afternoon. If the gradient
continues to strengthen, gusts may increase beyond 30 knots. This
will be something to watch closely over the next few hours.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR through the TAF period. Winds out of
the NW and moderate around 12-15 knots. Some higher gusts are
possible, though do not look to be as prevailing compared to
terminals to the north. Winds ease into the late night to below 10
knots.

&&

.MARINE...
(Tonight through next Sunday)
Issued at 1220 PM PDT Tue Apr 30 2024

Strong winds persist through Friday, with gale force gusts of 40
to 45 knots are possible over the outer waters and portions of the
immediate coast near Point Reyes and Point Sur through much of the
week. The strong winds will result in hazardous seas and steep
wind waves with significant wave heights reaching 10 to 14 feet
in the outer waters. Conditions will gradually improve over the
weekend and into next week as winds begin to ease. Chances of rain
begin early Saturday as a trough descends over the region.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Wednesday for SF Bay N of
     Bay Bridge.

     Small Craft Advisory until 3 AM PDT Wednesday for Mry Bay-Pigeon
     Pt to Pt Pinos 0-10 nm.

     Small Craft Advisory from 9 AM to 9 PM PDT Wednesday for Mry Bay.

     Gale Warning until 3 AM PDT Wednesday for Pt Arena to Pt Reyes 0-
     10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

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

     Gale Warning until 9 PM PDT Wednesday for Pt Pinos to Pt Piedras
     Blancas 0-10 nm.

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

&&

$$

SHORT TERM...Canepa
LONG TERM....Canepa
AVIATION...AC
MARINE...AC

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