-- Discussion containing changed information from previous version are highlighted. --
916
FXUS66 KMTR 231744
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1044 AM PDT Sun Jun 23 2024

...New AVIATION...

.SYNOPSIS...
Issued at 237 AM PDT Sun Jun 23 2024

Somewhat cooler temperatures in the interior today, continuing into
the beginning of the work week with a slight cooldown midweek. Very
low chance of elevated convection and associated dry lightning in
the southern Central Coast.

&&

.UPDATE...
Issued at 902 AM PDT Sun Jun 23 2024

Visibilities continue to improve over inland areas of the region and
therefore the Dense Fog Advisory for the Monterey Bay and areas
surrounding was allowed to expire at 9 AM PDT. However, if
encountering dense fog on area highways; slow down, use your
headlights, and leave plenty of distance ahead of you. Otherwise,
low clouds have retreated to the coast with clear sky conditions
inland. The ongoing forecast for the short term remains on track
with no updates anticipated this morning.

&&

.SHORT TERM...
(Today and tonight)
Issued at 237 AM PDT Sun Jun 23 2024

Skies remain generally clear throughout the region, save for stratus
that has developed around the Monterey Bay region, and stratus
development for the rest of the morning is limited to the coast and
potentially the North Bay valleys and northern SF Bay region. Low
temperatures tonight range from the low to mid 50s in the lower
elevations to the 60s to low 70s in the higher elevations. With the
upper level ridge moving off to the east, highs will be somewhat
cooler today, with highs in the upper 80s to mid 90s in the interior
valleys, perhaps close to 100 in the warmest spots, with highs in
the 70s expected across the Bayshore and the mid 50s to mid 60s
across the Pacific coast.

The main forecast issue continues to be the potential for elevated
convection over the southern sections of Monterey and San Benito
counties this afternoon and evening. A shot of mid-level moisture
will come into the region from the south, ahead of a weak upper
level trough. The latest 3km NAM forecast soundings for Paso Robles
continue to show a moistening low to mid layer and respectable lapse
rates. Below the moist layer, conditions remain dry, which will
hamper any precipitation from any cells that pop up, but will also
raise the risk of dry lightning, especially with MUCAPE levels above
1000 J/kg. All that said, the potential for any storms to develop
continues to be low, hovering around 10-15%. One factor that limits
storm potential is that the synoptic forcing remains to our north
and west, requiring any storms that do develop to be topographically-
driven. Confidence in any fire weather concerns remains too low to
message as a fire weather headline. The day shift will take another
look at the forecast as updated model output comes in.

&&

.LONG TERM...
(Monday through Saturday)
Issued at 237 AM PDT Sun Jun 23 2024

The mid-layer moisture continues to push through the region and will
push across the Bay Area on Tuesday. In addition to the mid- to
upper level clouds that will typically accompany the moisture, the
chance for elevated convection mainly across the Central Coast
remains through Tuesday, although as with Sunday, the chances are
very low. Interior temperatures will cool off on Wednesday and
Thursday, with highs in the 80s to the mid 90s, as an upper level
trough comes into the West Coast and promotes improved onshore flow.
CPC outlooks continue to suggest that temperatures above seasonal
averages will continue into the first week of July.

&&

.AVIATION...
-- Changed Discussion --
(18Z TAFS)
Issued at 1043 AM PDT Sun Jun 23 2024

VFR across the board with stratus and IFR-LIFR conditions to return
overnight. Patchy fog is likely to develop across the North Bay
tonight with reduced visibilities and ceiling heights expected at
STS and APC. Moderate confidence that fog will impact STS, low to
moderate confidence that fog will impact APC. Guidance indicates
stratus may potentially reach SFO and OAK overnight but confidence
is low to moderate. Marine layer depth should remain similar to last
night which did not see stratus reach SFO or OAK. Current thinking
is that forecast RH values will be high enough to support scattered
low level clouds with stratus being confined closer to the
coastline. Onshore winds last through the TAF period with winds
becoming more moderate during the day before weakening and becoming
light overnight.

Vicinity of SFO...VFR with low confidence that MVFR-IFR CIGs will
develop overnight. Guidance was split on if CIGs will reach SFO
overnight with NBM and GLAMP taking the most progressive stance on
widespread stratus cover. Leaning towards stratus staying confined
closer to the coast due to a fairly compressed marine layer but
forecast RH values support scattered low level clouds overnight.
Onshore flow prevails through the TAF period with winds out of the
west and northwest expected. Winds becoming more moderate during the
day before weakening overnight.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR becoming IFR-LIFR overnight. Onshore
flow prevails through the TAF period with moderate winds during the
day becoming light overnight. Stratus is expected to return tonight
by the late evening at MRY and overnight at SNS. Confidence is
slightly lower on the timing of stratus arrival. Guidance indicated
a wide time range between 04Z to 08Z for stratus to arrive at MRY
and a slightly shorter time frame for stratus arrival at SNS between
08Z to 11Z.
-- End Changed Discussion --

&&

.MARINE...
(Today through Friday)
Issued at 902 AM PDT Sun Jun 23 2024

Hazardous conditions for small crafts persist across the northern
coastal waters through the early work week. Strong northwest to
northerly winds continue over the northern coastal outer waters.
Fresh gusts remain possible over the southern outer waters and
portions of the northern interior coastal waters. Winds will
strengthen over the northern coastal waters today with strong to
near gale force gusts possible through Monday morning. Significant
wave heights over the northern waters will gradually build to
10-11 feet Sunday into Monday before beginning to diminish
Tuesday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 PM PDT this evening for Pt Arena to
     Pt Reyes 0-10 nm-SF Bay N of Bay Bridge.

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

&&

$$

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

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