971
FXUS66 KMTR 092055
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
155 PM PDT Sun Jun 9 2024

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

.SYNOPSIS...
Issued at 107 PM PDT Sun Jun 9 2024

Warmer temperatures are in store Monday-Wednesday before a return
to seasonal averages late week.

&&

.SHORT TERM...
(This evening through Monday)
Issued at 107 PM PDT Sun Jun 9 2024

One more pleasant day before the heat returns.

A short wave trough axis at 500 mb is now directly above the Bay
Area. This is evident in the convective clouds over the Sierra
moving to the NE and the stratocumulus over the ocean moving the
the S. Locally, satellite imagery that shows most clouds have
cleared, with the exception of the SF Peninsula coastline. The
Ft. Ord profiler is measuring the marine layer at 2,100 ft deep.
This is helping keep temperatures in the 60s along the coast and
adjacent valleys. Inland areas are in the upper 70s, and will take
advantage of the clear skies to get into the mid-80s later this
afternoon. Onshore winds will also begin to increase as the higher
surface temperature allows more downward momentum transfer.

The short wave trough will continue to amplify and become a cut-
off low west of the Channel Islands by Monday morning. This will
allow a high pressure ridge to move in north of the low. This
ridge will warm the air mass through both normal subsidence and
by interacting with the cut-off low to generate some weak
offshore flow around 700 mb. This effect is most evident in the
North Bay where a tongue of higher thickness values will spill
over from Nevada. Monday is the first day of the heat spell, with
temperatures expected to reach the high 80s and lower 90s inland.

&&

.LONG TERM...
(Monday night through next Saturday)
Issued at 107 PM PDT Sun Jun 9 2024

Temperatures will cool off quite a bit Monday night, retreating
back to near normal values in the 50s. This will be a theme of the
event with high afternoon temperatures, but good relief overnight.
Unlike the worst heat waves, there will be an opportunity to open
the windows after dinner.

Tuesday looks to be the hottest day and has most of our attention.
Mid to upper 90s are expected for inland areas, as well as low
100s in the northern portions of Sonoma and Napa counties, the
southern Salinas valley and San Benito county, and more generally
along the easternmost portions of counties bordering the Central
Valley. Warm temperatures persist into Wednesday, but begin to
drop by a few degrees, with high temps largely similar to those on
Monday. Coastal areas throughout this event will remain
relatively cool in the mid to upper 60s, perhaps touching the
lower 70s on Tuesday as onshore flow helps maintain more
comfortable temperatures. As it currently stands, models continue
to show light onshore flow persisting at the surface.

With these warmer temperatures comes increased HeatRisk. While
Monday and Wednesday see largely Minor HeatRisk for the majority of
our area, Tuesday will have many inland locations achieving Moderate
levels of HeatRisk while coastal areas remain in the Minor category.
This moderate category indicates a level of heat that affects most
individuals sensitive to heat, such as those that are ill, elderly,
very young, or without shelter or a means to cool themselves such as
air conditioning. As we draw nearer to this event, keep in mind that
even if only Minor HeatRisk is indicated, that heat related illness
and impacts can affect anyone, especially when heat is prolonged.
Its never a bad idea to make sure you are staying adequately
hydrated during times of warmer temperatures, taking breaks in the
shade if working outdoors, and to check in on loved ones who perhaps
fall into the demographics of those sensitive to heat. Additionally,
if planning to visit the coast or a body of water to cool off, make
sure you wear a life jacket, swim near a lifeguard, and be aware
of the risks of cold water shock.

By Thursday, high temperatures decrease and begin to cool off as
troughing resumes and the cutoff low rejoins upper level flow and
lifts out to our east. Sweet relief.

&&

.AVIATION...
(18Z TAFS)
Issued at 1022 AM PDT Sun Jun 9 2024

Lingering low and mid level clouds as a weak upper level trough
exits the area. VFR through the day today with breezy onshore flow
for coastal and gap areas. Moderate confidence in return of
MVFR/IFR stratus overnight by about sunset for Bay Area terminals,
slightly later for North Bay. All terminals clearing to VFR by mid
morning Monday.

Vicinity of SFO...VFR through this afternoon with some occasional
lingering low clouds. Breezy onshore W/NW flow with gusts around
25 kts this afternoon, diminishing into the evening. Moderate
confidence in MVFR/IFR stratus around sunset (high confidence in
cigs, lower confidence in timing).

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR through the afternoon with light
onshore flow. High confidence in MVFR/IFR cigs overnight tonight
and clearing to VFR once again by late Monday morning.

&&

.MARINE...
(Today through Friday)
Issued at 1022 AM PDT Sun Jun 9 2024

The gradient between subtropical high pressure in the East
Pacific, and lower pressure over the western US is supporting a
fresh to strong NW breeze and rough seas across the coastal
waters. The overall pattern will remain fairly stable over the
next week although the high pressure will meander closer to the
coast at times, bringing periods of near gale force winds and
very rough seas. The first push is expected mid-week, with another
over the upcoming weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 PM PDT this evening for Mry Bay.

     Small Craft Advisory until 3 AM PDT Tuesday for Pigeon Pt to Pt
     Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm.

     Small Craft Advisory until 9 AM PDT Monday for Pt Pinos to Pt
     Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

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

     Small Craft Advisory until 9 AM PDT Tuesday for Pt Arena to Pt
     Reyes 10-60 NM.

&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...Behringer
MARINE...Flynn

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