706
FXUS66 KMTR 242340
AFDMTR

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

...New UPDATE, AVIATION, FIRE WEATHER...

.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...
(00Z TAFS)
Issued at 433 PM PDT Mon Jun 24 2024

Satellite shows mostly clear skies over the region with a band of
high-based convection clouds moving north from the south. Therefore,
there is a slight chance for dry thunder and lightening. Conditions
will remain VFR through the TAF period for all terminals, except
Monterey Bay terminals where low stratus will return tonight. Models
hint that low ceilings will return for the remainder of the
terminals tonight, but due to lack of model agreement and
persistence, VFR was kept in the TAFs. Moderate to breezy onshore
winds will diminish to light and variable tonight. Winds will
rebuild by Tuesday afternoon.

Vicinity of SFO...VFR through the TAF period models hint at MVFR
developing early Monday morning, but will monitor if any updates are
needed to TAFs. NW strong winds will diminish tonight before
rebuilding to breezy Tuesday afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR until tonight where IFR conditions are
expected to return. Timing of clearing is uncertain as models show
disagreement but moderate confidence that clearing will occur near
14-15Z.

&&

.MARINE...
(Today through Saturday)
Issued at 910 AM PDT Mon Jun 24 2024

Hazardous conditions for small crafts persist across the northern
coastal waters through early week. Fresh to strong north to
northwest winds continue over the northern coastal waters.
Moderate northwest winds continue over the southern coastal waters
with the occasional fresh gust possible over the outer waters.
Significant wave heights over the northern waters will build to
10-11 feet through today before wave heights abate below 10 feet
by Tuesday. Widespread fresh to strong winds are expected to
return over the coastal waters by late week with wave heights
gradually building to 10 feet across portions of the northern
coastal waters.

&&

.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/RGass
LONG TERM....RGass/DialH
AVIATION...SO
MARINE...SO/Kennedy

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