661
FXUS66 KMTR 061610
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
910 AM PDT Thu Jun 6 2024

...New UPDATE...

.SYNOPSIS...
Issued at 215 AM PDT Thu Jun 6 2024

Hot inland otherwise expecting the beginning of a cooling trend
today mainly on the coastline then cooling reaches further inland
Friday through Sunday. Another potential hot period mid next week.

&&

.UPDATE...
Issued at 905 AM PDT Thu Jun 6 2024

Forecast looks on track today, overall running about 5-10 degrees
cooler than 24 hours ago. Still warm today with minor to moderate
Heat Risk for most. Some haze currently being observed may act to
keep temps a bit cooler than expected for areas more near the
coast. Still looking like we`ll shave off another 3-5 degrees for
tomorrow.

&&

.SHORT TERM...
(Today and tonight)
Issued at 259 AM PDT Thu Jun 6 2024

There are markedly different temperatures across the Bay Area and
north Central Coast depending on your location this morning. For
example there`s as much as 36F degree difference in temperatures
from 83F on Mt Tam (within the lower level temperature inversion -
a result of large scale sinking motion with the high pressure
system) vs mid 50s to upper 40s near sea level (due to a chilly
maritime influence) in Marin county at 2 am. Similarly it`s in the
lower 80s elsewhere along the ridgetops of the Bay Area, however
again it`s generally cooler with light breezes closer to sea level
nearest the bay and especially along the coastline.

Surface winds are settling in to a new regime in response to newly
developing adjustments in surface pressure gradients. Northerly
and southerly directed winds will join with the onshore wind and
begin to steepen today, this will bring about cooling from sea
level up through about 2500 feet today, best chances of this along
the immediate coast. At the moment, will let the Heat Advisory
continue as is, but we are closing in on the time when we can
think about reducing some of its coverage, possibly more so during
the day shift and/or evening shift. On the mid shift we`ll
continue to closely monitor the development of coastal stratus and
fog and marine layer depth.

Seeing the northerly pressure gradient gradually reducing is a
good sign, which will help give more equal weight to the onshore
gradient and wind today, the NAM forecasts the SFO-SAC gradient
to near 4 mb this afternoon. Sea surface temps in our coastal
waters vary from a few upper 40s to lower 50s, nice and chilly
which helps provide good potential for a sea breeze. HREF output
shows more coastal stratus and fog tonight.

&&

.LONG TERM...
(Friday through Wednesday)
Issued at 259 AM PDT Thu Jun 6 2024

A cooling trend continues into the weekend, onshore breezes will
extend farther inland. Daytime highs on the coastline cooler than
typical for this time in June, inland daytime highs will also cool
back to near typical in June. Weak upper level troughing moves across
the forecast area over the weekend then the global models forecast
increasing high pressure redeveloping over northern California early
to mid next week.

&&

.AVIATION...
(12Z TAFS)
Issued at 438 AM PDT Thu Jun 6 2024

Sky condition is VFR mixed with MVFR surface visibility in haze
along the coastline. Microphysics satellite imagery shows stratus
and fog slowly moving northward along the Big Sur Coast connected
to an extensive pool of stratus and fog from Point Conception and
areas to the southeast through southwest. Also, a few patches of
coastal stratus and fog are forming around the Monterey Bay and in
the Bay Area near the Golden Gate and in the North Bay. In our
forecast area the marine layer depth varies from a few hundred
feet along the coast of the North Bay to 1,000 feet along the
north Central Coast. Bodega Bay and Fort Ord profilers and
Wednesday evening`s Oakland upper sounding show the marine layer
temperature inversion is still strong. The ACV-SFO pressure
gradient (northerly wind) is diminishing to 4.6 mb, the SBA-SFO
and SMX-SFO pressure gradients (southerly wind) are 2.1 mb and 1.7
mb respectively, while the SFO-SAC pressure gradient is onshore
at 2.2 mb.

As of current, the meso-scale model output are under-forecasting
the aforementioned southerly pressure gradient(s) by at least 50%.
With the newly developed combined northerly and (under-forecasted)
southerly wind potential coupled to the onshore wind, am expecting
at least what the meso-scale models show for cooling at 1000 mb
(~300 feet) and at 925 mb (~2500 feet), therefore the lower level
temperature inversion should weaken somewhat today below the 850
mb level (~5000 feet). Bottom line, this and current nocturnal
radiative cooling provides coastal stratus and fog /VLIFR-IFR/ a
foothold for additional development through daybreak, then mixing
out temporarily during the day with the usual vertical mixing then
redeveloping tonight and Friday morning.

Vicinity of SFO...VFR. West wind 10 to 15 knots through this morning,
increasing to 18 to 25 knots in the afternoon and evening. West
wind decreasing tonight and early Friday morning to near 10 knots.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...LIFR-IFR developing early this morning,
stratus and fog mixing out 16z-17z to VFR during the day. West to
northwest winds in the afternoon, possibly shifting to southwest
at KMRY depending how strong the southerly wind reversal is during
the day. KSNS surface wind northwesterly and becoming gusty in the
afternoon. Stratus /MVFR-IFR/ forecast this evening and likely to
continue tonight and Friday morning.

&&

.MARINE...
(Tonight through next Tuesday)
Issued at 220 AM PDT Thu Jun 6 2024

Expect breezy northerly winds to persist through the day before
gradually easing into Friday. These winds along with rough seas
will lead to hazardous conditions for small craft. A moderate
period Northwest swell will continue impact the coastal waters
but will diminish Friday through Saturday before waves build
again towards the end of the period.

&&

.BEACHES...
Issued at 222 AM PDT Thu Jun 6 2024

A Beach Hazards Statement is in effect through Thursday evening.

Forecast remains on track. Moderate period swell is entering the
coastal waters at 14-17 seconds with heights varying 7-11 feet.
The would generate breaking waves of 8-15 feet with locally
higher waves at favored break points. Sneaker waves can run over
100 ft up a dry beach, pulling people in the water from rocks,
jetties, and beaches. Inexperienced swimmers should stay out of
the water. Observe the ocean for 20 minutes before relaxing on the
beach. The hot weather inland will lead to more people visiting
the beach this week. Know where lifeguards are, obey their
instructions, and never turn your back on the ocean!

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through this evening for CAZ006-505-509-
     530.

     Heat Advisory until midnight PDT tonight for CAZ503-504-506-510-
     512>516-518.

PZ...Small Craft Advisory until 3 AM PDT Friday for Pt Arena to Pt
     Reyes 0-10 nm.

     Small Craft Advisory until 9 PM PDT this evening for Pigeon Pt
     to Pt Pinos 10-60 NM-Pt Reyes to Pigeon Pt 0-10 nm.

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

&&

$$

UPDATE...Behringer
SHORT TERM...Canepa
LONG TERM....Canepa
AVIATION...Canepa
MARINE...Murdock

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