420
FXUS66 KMTR 092337
AFDMTR

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

...New AVIATION, MARINE...

.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...
(00Z TAFS)
Issued at 436 PM PDT Sun Jun 9 2024

Moderate-high confidence in IFR/MVFR stratus impacting all terminals
overnight with the exception of LVK and SJC. Winds will remain
onshore through the TAF period. Widespread VFR to prevail by late
morning tomorrow.

Vicinity of SFO...High confidence in MVFR stratus making an early
return this evening, lower confidence in IFR developing. VFR to
prevail by mid-to-late morning tomorrow. Winds will diminish
overnight and briefly become offshore by mid-morning tomorrow before
prevailing out of the west by tomorrow afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...High confidence in IFR stratus making an
early return this evening. Westerly winds will prevail through the
TAF period. VFR to prevail by late morning tomorrow.

&&

.MARINE...
(Tonight through next Friday)
Issued at 436 PM PDT Sun Jun 9 2024

The pressure gradient between subtropical high pressure over the
Eastern Pacific Ocean and lower pressure over the western United
States is supporting a fresh to strong northwesterly 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...Heat Advisory from 11 AM to 8 PM PDT Tuesday for CAZ504-506-510-
     513>515-518.

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 Pigeon Pt to Pt
     Pinos 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm-Pt
     Reyes to Pigeon Pt 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...Sarment
MARINE...Sarment

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/nwsbayarea
www.twitter.com/nwsbayarea
www.youtube.com/nwsbayarea