-- Discussion containing changed information from previous version are highlighted. --
037
FXUS66 KMTR 221756
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1056 AM PDT Sat Jun 22 2024

...New AVIATION...

.SYNOPSIS...
Issued at 1250 AM PDT Sat Jun 22 2024

Hot temperatures peak today with a Heat Advisory in effect later
this morning through the evening for the interior regions with a
moderate risk of heat-related illnesses. Temperatures moderate
through the early part of next week, but remain warm across the
interior.

&&

.UPDATE...
Issued at 851 AM PDT Sat Jun 22 2024

Ceilings are lower than this time yesterday with areas of patchy
fog, yet less of an inland extent to the cloud cover. However,
conditions are quickly mixing out over inland areas and will
continue this trend with more breaks in the cloud cover near the
coast this afternoon. As such, inland areas remain under a Heat
Advisory from 11 AM this morning until 10 PM this evening as
HeatRisk reaches into the moderate category. That said, the ongoing
forecast remains on track with no updates anticipated this morning.

&&

.SHORT TERM...
(Today and tonight)
Issued at 1250 AM PDT Sat Jun 22 2024

Satellite imagery shows marine layer stratus developing across the
coastal regions with intrusions through the Golden Gate, across the
East Bayshore, into Napa County, across the Monterey Bay region and
down into the Salinas Valley. Right now, we`re not expecting as much
interior development tonight, as the marine layer has compressed
through the previous day, as exemplified by the Fort Ord profiler
showing a marine layer depth around 1000-1250 feet. Low temperatures
this morning range from the low 50s to near 60 in the lower
elevations, with the lower temperatures expected where there is
marine layer stratus tonight, up to the upper 60s to lower 70s in
the higher elevations.

The warmest temperatures of the brief heat event are expected to
develop later today. A Heat Advisory will come into effect later
this morning through the evening for the interior North Bay
mountains, interior East Bay, the Santa Clara Valley and eastern
Santa Clara hills, the interior Central Coast mountains, the
southern Salinas Valley, and the Santa Lucia mountains. Areas under
the Heat Advisory should expect highs from the mid 90s into the mid
100s, and a Moderate HeatRisk. This means that there is a risk of
heat-related illnesses for most people sensitive to heat, including
children, the elderly, pregnant women, those working or living
outside, and those with certain medical conditions. Elsewhere across
the region, high temperatures are expected to reach the upper 80s to
mid 90s in the inland North Bay valleys, the mid 70s to upper 80s in
the Bayshore and the northern Salinas Valley, and the 60s into the
low 70s for the Pacific coast.

Here are heat safety tips:

* Stay hydrated and drink plenty of fluids.
* Wear lightweight, light-colored clothing.
* Reduce time spent outdoors or stay in the shade.
* Never leave people or pets unattended in vehicles.
* Use sunscreen if going to the coast or the pool.

&&

.LONG TERM...
(Sunday through Friday)
Issued at 1250 AM PDT Sat Jun 22 2024

Sunday should be noticeably cooler as an upper level trough to our
west begins to promote stronger onshore flow. High temperatures will
drop into the mid 80s to the low 90s in the interior valleys
(perhaps close to 100 in the warmest spots), the 70s into the lower
80s along the Bayshore, and the upper 50s to the 60s along the
coast. The ridge will begin to erode and shift eastward with an
upper level low approaching the Pacific Northwest, but the general
weather pattern should remain relatively unchanged, with perhaps a
few degrees of cooling towards the latter part of the next work
week. The latest CPC outlook continues to suggest temperatures near
or above seasonal averages, and precipitation at or below seasonal
averages (noting that at this point in the year, seasonal average
precipitation is very low) continue into the first days of July.

&&

.AVIATION...
-- Changed Discussion --
(18Z TAFS)
Issued at 1055 AM PDT Sat Jun 22 2024

VFR across the board with stratus and MVFR-LIFR conditions returning
across portions of the Bay Area and Central Coast tonight. Moderate
confidence that stratus will reach OAK, SFO, MRY, and SNS but not
extend into STS, LVK, or SJC. Low to moderate confidence that
stratus will reach APC. For now, expecting similar stratus coverage
at APC tomorrow as seen today with NBM and HREF showing stratus
moving up the delta and reaching APC around 11/12Z. Breezy onshore
flow will return this afternoon before light northwest to, at times,
variable winds return overnight.

Vicinity of SFO...VFR becoming MVFR-IFR overnight. Stratus is
currently expected to reach SFO overnight but confidence is
currently moderate, bordering low to moderate. The main uncertainty
comes from the depth of the marine layer which is expected to
compress further tonight. Currently, the top of the marine layer is
around 1000 ft which allowed stratus to reach SFO this morning. If
the marine layer compresses closer to a depth of 500 ft, as
currently forecast, stratus coverage may be confined closer to the
coast/potentially not reach SFO. Weak northerly to northeasterly
winds will continue through the remainder of the morning before
moderate westerly to northwesterly return early this afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR becoming MVFR-LIFR overnight. Moderate
to high confidence that stratus will return overnight with low to
moderate confidence on timing. Stratus looks to return by late this
evening at MRY and during the early morning at SNS. For MRY, models
indicated cloud coverage may fluctuate between few/scattered and
broken/overcast roughly between 03-10Z with confidence increasing in
overcast conditions from 10Z onwards. Currently leaning towards
broken/overcast conditions prevailing from 03-10Z but cannot rule
out cloud coverage temporarily becoming more scattered. Onshore flow
continues with moderate afternoon winds becoming light and variable
overnight.
-- End Changed Discussion --

&&

.MARINE...
(Today through Thursday)
Issued at 851 AM PDT Sat Jun 22 2024

Strong, northwest winds with near gale force gusts possible
continue into the work week over the northern outer coastal
waters. Fresh to the occasional strong gusts remain possible over
the southern outer coastal waters and portions of the northern
interior coastal waters. Elevated wave heights between 10 to 12
feet continue over the northern outer waters with significant wave
heights expected to diminish below 10 feet by the middle of the
work week. Conditions hazardous to small crafts will remain
possible through the middle of the work week across the northern
outer coastal waters. Light southerly swell continues to move
through the waters, accompanied by moderate NW swell through the
beginning of next week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 10 PM PDT this evening for CAZ504-510-
     513>518.

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

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

&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Kennedy
MARINE...Kennedy

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