877
FXUS66 KMTR 250548
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1048 PM PDT Mon Jun 24 2024

...New AVIATION, MARINE...

.SYNOPSIS...
Issued at 142 PM PDT Mon Jun 24 2024

Temperatures near to slightly above seasonal averages with a slight
cooldown midweek. Very low chance of high-based convection and
associated dry lightning in the Central Coast today. The threat will
shift northward into the Bay Area and North Bay tonight into Tuesday
evening.

&&

.UPDATE...
Issued at 433 PM PDT Mon Jun 24 2024

Forecast update to add slight chance of thunderstorms into Tuesday
for portions of our service area. Radar is showing high based
shower this afternoon with one strike so far over the Santa Cruz
Mountains. Models are indicating that showers will continue
overnight and through much of Tuesday while slowly transiting
north and east.

&&

.SHORT TERM...
(This evening through Tuesday)
Issued at 142 PM PDT Mon Jun 24 2024

We continue to see a small threat (10-15%) for high-based convection
across Monterey and San Benito County this afternoon and that threat
will shift northward throughout the night and into tomorrow morning,
potentially into the afternoon/evening as well. This is as mid-level
moisture is being advected in from the south and will move across
the entire Bay Area through Tuesday evening with forecast MUCAPE
between 100-300 J/kg. Mid-level moisture is the most certain
ingredient, with a plume of moisture migrating northwards with PWAT
values up to 1-1.25". For context, if those values were reported at
our upper air site at Oakland airport, those precipitable water
values would be at or above the 90th percentile value for all
observed soundings at this time of year. The main impact if
convection does develop would be the possibility for dry lightning
setting off grass and shrub fires, but this is a "low confidence-
high impact" type of event at this stage.

Otherwise, temperatures are expected to be near seasonal averages
for coastal areas and slightly above for the interior the next
several days with most areas away from the coast only getting to
Minor HeatRisk.

&&

.LONG TERM...
(Tuesday night through Sunday)
Issued at 1243 AM PDT Mon Jun 24 2024

Wednesday sees an upper level trough move in which will push the
moisture out of our region, and herald a gradual cooling trend in
temperatures for the interior regions. By the end of the week,
temperatures across the interior will top out at around 90 in the
warmest spots, with most of the inland valleys seeing temperatures
within the 80s. Towards the beginning of July, model ensemble
clusters are indicating a couple of ridges approaching the West
Coast, with early indications of a warming trend towards the end of
the 7-day forecast.

&&

.AVIATION...
(06Z TAFS)
Issued at 1047 PM PDT Mon Jun 24 2024

The most important thing this TAF cycle is the low confidence-high
impact possibility for high-based convection. Otherwise, currently
VFR at all terminals except MRY. VFR through the TAF period at all
terminals except the Monterey Bay terminals of MRY and SNS which
will likely see LIFR conditions overnight. Winds become variable
overnight but otherwise remain onshore through the TAF period.

Vicinity of SFO...Currently VFR with northwesterly flow. VFR through
the TAF period. Winds will prevail out of the west/northwest through
the TAF period, becoming gusty tomorrow afternoon. Low confidence on
MVFR stratus impacting the terminal in the early-to-mid morning
hours.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Currently LIFR with northerly flow at MRY
and VFR with northwesterly flow at SNS. Winds become variable
overnight before prevailing out of the west/northwest by mid-morning
tomorrow. LIFR conditions will likely impact both terminals through
the mid-morning hours.

&&

.MARINE...
(Tonight through next Sunday)
Issued at 1047 PM PDT Mon Jun 24 2024

  Hazardous conditions for small crafts persist across the
northern  coastal waters through Tuesday morning then diminish
Tuesday afternoon. Fresh to strong northwest winds continue over
the  northern coastal waters while moderate northwest winds
continue  over the southern coastal waters. Wave heights will
begin to  diminish below 10 feet by Tuesday. Conditions hazardous
to small  crafts are likely to return by mid to late week with
widespread  fresh to strong winds expected over the coastal waters
Wednesday  and continuing into the weekend.

&&

.FIRE WEATHER...
Issued at 433 PM PDT Mon Jun 24 2024

Slight chance of thunderstorms were added to the forecast through
Tuesday. While these thunderstorms will be accompanied by showers,
it is possible that rain will be limited. So far convection that
has occurred in southern areas has shown measurable
precipitation. Winds at 4 pm today have been gusting into the 20
mph range in the mountains, but single digits in the low lands.
Any strikes that do occur may cause a fire start in the fine
fuels. The additional concern is any strikes in the fine fuels
that sleep for a few days when the onshore winds kick in. This
could cause rapid growth in the grasses even with higher humidity.
No strike or spark, no fire.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 AM PDT Tuesday for Pt Arena to Pt
     Reyes 10-60 NM.

&&

$$

SHORT TERM...BFG
LONG TERM....RGass
AVIATION...Sarment
MARINE...SO

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