810
FXUS66 KMTR 021541
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
841 AM PDT Thu May 2 2024

...New UPDATE, MARINE...

.SYNOPSIS...
Issued at 307 AM PDT Thu May 2 2024

A ridge of high pressure will keep daytime temperatures mild to
warm across the region throughout late week. Breezy onshore winds
will keep temperatures cooler near the coast. Wet, unsettled
conditions returning Friday night into Saturday, much cooler
inland Saturday. Unseasonably cool daytime highs continuing into
early next week then gradually warming by the middle of the week.

&&

.UPDATE...
Issued at 841 AM PDT Thu May 2 2024

Quick update for this morning. Satellite shows largely clear skies
across the CWA. Today and Friday`s highs still expected to be on the
warm, but pleasant side with interior regions seeing max temps in
the upper 70s to low 80s. Closer to the coast, highs will be in the
60s with breezy northwest winds. That being said, enjoy the warm
temperatures and sunshine today and tomorrow! Saturday, light and
beneficial rain accompanied by overcast conditions are still
expected over the region. All for now.

&&

.SHORT TERM...
(Today and tonight)
Issued at 349 AM PDT Thu May 2 2024

Dry air, a continental influence is remaining locked in over the
forecast area. The northerly 5.9 mb ACV-SFO and 2.6 mb UKI-STS
pressure gradients are resulting in dry northerly wind flow, over
the coastal waters gale warnings continue. Seeing some increases
in water vapor and stratus/fog development over the coastal waters
per recent satellite imagery while drier air/clear sky is still
prevailing closer to the coastline. A trough moving across northernmost
CA/OR will ease the ACV-SFO pressure gradient a little today and
tonight, the UKI-STS gradient not really easing until tonight.

Lower to mid level ridging continues through tonight. A lower level
temperature inversion within 500-800 feet of the surface is seen on
the Bodega Bay and Fort Ord profilers. Early May insolation tapping
the lower level inversion will bring daytime temperatures back up a
few degrees above early May normals inland. It`ll remain cooler along
the coast today. Highs 60s coastside, 70s to lower 80s inland.

&&

.LONG TERM...
(Friday through Wednesday)
Issued at 349 AM PDT Thu May 2 2024

Seeing good global and mesoscale model agreement, one long wave
trough is now stationary along the West Coast, part of an unsteady
northern hemispheric long wave trough pattern. A low pressure
system from the Aleutian Islands will move through the long wave
trough and bring rain to our forecast area Friday night and
Saturday. Rain developing first over the North Bay Friday night,
rain quickly spreading southeastward across much of the rest of
the forecast area Saturday. Expect noticeably cooler temperatures
especially inland Saturday with daytime highs in the upper 50s to
mid 60s, warmest southern interior; daytime temperatures 5F to 15F
below early May normals. The low is still expected to brush by
and tap higher levels of water vapor extending far north of
Hawaii, while retaining a strong mid-latitude influence e.g. it`s
an appreciably cold core system up through the 700 mb level by
comparison on Oakland upper air climatology, the pool of cold air
a little more compact by the 500 mb level. Unlikely there`ll be
layer instability extending above 700 mb, forecast 700-500 mb
lapse rates are low and much more stable. Recent precipitable
water values on the GFS maintain between 1.00" and 1.10" Saturday,
not far from the max moving average on Oakland upper air sounding
climatology in early May.

Seeing some recent increases in model forecast rainfall amounts.
For example over 0.50" to 1" rain totals North Bay, near 0.50" low
elevations and up to 0.75" to 1" East Bay hills/mountains and the
Santa Cruz Mountains, 0.10" to 0.20" interior north Central Coast to
around 0.50" Big Sur Coast. The Bay Area and northernmost north
Central Coast may receive over half if not nearly May normal
precipitation from this system if current QPF verifies. As mentioned
expect wet and cooler weather Saturday, gusty northwest winds over
the coast temporarily subsiding with the passage of a surface cold
front/trough.

Chilly to cold overnight low temperatures for the time of year (40s
coastside and bayside / 30s inland) are forecast late Saturday night
to Sunday morning and Sunday night to Monday morning. San Francisco
and Oakland downtown possibly including a few other locations may be
nearing record lows Sunday and Monday mornings. Stay tuned to updates,
right now Sun-Mon mornings look to be the chilliest. Forecast temperature
guidance could edge a little lower between now and late weekend.

Otherwise dry weather returns Sunday. The surface pressure pattern
favors gusty northwest winds redeveloping over the coastal waters
late in the weekend and continuing early next week. Daytime highs
gradually warming by the middle of next week.

&&

.AVIATION...
(12Z TAFS)
Issued at 417 AM PDT Thu May 2 2024

Generally VFR through the afternoon, with breezy northwest winds
building through the day, gusting to 20-25 knots this afternoon and
evening. Marginal LLWS concerns in the North Bay this evening, but
shear magnitudes are too small to include in the TAFs. Expect
stratus to fill towards and at the immediate coastline through the
evening ans into Friday morning, as a trough approaches the region.

Vicinity of SFO... VFR through the TAF period. West-northwest winds
building through the day with gusts to 30 knots. A low confidence
(20-30% probability) that wind gusts exceed 35 knots at the
terminal. Model output shows some stratus streaming through the
Golden Gate and San Bruno Gap this evening, but confidence is low,
with OAK and SJC having slightly higher probabilities for MVFR-IFR
ceilings, noting that "slightly higher" in this case only goes up to
10-20%.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... VFR through the afternoon, with westerly
winds building through the day, gusting to 25 knots. IFR-LIFR
stratus builds at the coast and across the Monterey Bay region
this evening, continuing through Friday morning.

&&

.MARINE...
(Today through Tuesday)
Issued at 841 AM PDT Thu May 2 2024

Strong winds persist throughout Friday, with gale force gusts of
40 to 45 knots possible. Strong winds will result in hazardous
seas and steep wind waves with significant wave heights reaching
10 to 13 feet in the outer waters. Conditions gradually improve
over the weekend and into next week as winds begin to ease. Rain
chances begin early Saturday as a trough descends over the region.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM Friday to 3 AM PDT Saturday for
     Mry Bay-SF Bay N of Bay Bridge.

     Small Craft Advisory until 3 AM PDT Friday for Mry Bay.

     Gale Warning until 9 PM PDT this evening for Pt Arena to Pt
     Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM-Pt Reyes to
     Pigeon Pt 0-10 nm.

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

     Gale Warning until 3 AM PDT Friday for Pigeon Pt to Pt Pinos 0-
     10 nm.

     Gale Warning until 3 AM PDT Friday for Pigeon Pt to Pt Pinos 10-
     60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm.

&&

$$

SHORT TERM...Canepa
LONG TERM....Canepa
AVIATION...DialH
MARINE...RGass

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