-- Discussion containing changed information from previous version are highlighted. --
785
FXUS66 KMTR 260353
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
853 PM PDT Tue Jun 25 2024

...New SYNOPSIS, UPDATE...

.SYNOPSIS...
-- Changed Discussion --
Issued at 220 PM PDT Tue Jun 25 2024

Cooler, seasonal to below average temperatures return Wednesday
and persist through the end of the week.
-- End Changed Discussion --

&&

.UPDATE...
-- Changed Discussion --
Issued at 853 PM PDT Tue Jun 25 2024

Showers over the North Bay have diminished. There were a few
isolated lightning strikes earlier today during the morning over
the Bay Area. Water vapor per the late afternoon Oakland upper air
sounding was primarily focused between 13000 and 22000 feet agl,
less vertical extent of focused water vapor compared to today`s
morning sounding. Today`s convection was distant remnants of
tropical storm Alberto that was over the southwestern Gulf of
Mexico last week, transported clockwise around the periphery of
the southern CONUS/northern Mexico high pressure system. At its
peak today, the precipitable water hovered near the 90th percentile
on long term late June Oakland upper air sounding climatology.

There`s good agreement in the global model forecasts that a low
amplitude zonal i.e. mainly west to east flowing polar jet stream
will continue across the northern CONUS/southern Canada this week,
a progressive pattern which will relatively suppress the aforementioned
southern latitude high pressure system allowing for slightly lower
500 mb heights and weak troughing over our forecast area. This will
also bring a return of drier mid-latitude influence across our forecast
area during the rest of the week. Onshore breezes will continue with
this pattern through mid-late week.
-- End Changed Discussion --

&&

.SHORT TERM...
(This evening through Wednesday)
Issued at 220 PM PDT Tue Jun 25 2024

Slight (10-15%) chance of thunderstorms producing dry lightning
continues over the Bay Area before chances diminish by the late
evening. Radar continues to show elevated cells moving over
Sonoma, Napa, and Marin Counties with the potential for isolated
thunderstorms continuing into the evening hours. For lightning
activity so far today, several strikes occurred in the vicinity of
the San Jose and Livermore airports this morning. Three airports
(San Francisco, Livermore, and San Jose) observed trace
precipitation overnight and again this morning, indicating some
precipitation is making it to the surface. However, precipitation
totals greater than a few hundredths of an inch are not
anticipated as most precipitation is expected to evaporate before
reaching the ground (creating a neat phenomenon known as virga).
Remember to stay weather aware and when thunder roars, go indoors!

Tuesday continues to be the warmest day this week with temperatures
cooling down beginning Wednesday. Tonight`s overnight low
temperatures, both inland and along the coast, will range from the
low to upper 50`s. Upper level troughing will move inland tonight
into tomorrow with temperatures cooling down to seasonal to slightly
below average. Wednesday`s inland high temperatures are expected to
be 3 to 7 degrees cooler than today`s with most areas seeing highs
in the upper 70`s to mid 80`s. Favored inland hot spots may see
temperatures reach the upper 80`s. Closer to the coast, cooler
temperatures prevail with highs largely in the upper 50`s to mid
60`s. As upper level troughing moves inland, the marine layer is
expected to deepen with increasing stratus chances along the
coastline and portions of the San Francisco Bay.

&&

.LONG TERM...
(Wednesday night through next Monday)
Issued at 220 PM PDT Tue Jun 25 2024

Upper level troughing will persist through late week with seasonal
to below average temperatures similar to Wednesday (upper 70`s to
mid 80`s inland and upper 50`s to mid 60`s along the coast)
continuing through Saturday. However, by Sunday, guidance continues
to indicate a warming trend will develop as upper level ridging
again builds over the West Coast. While this forecast is several
days out and subject to revision, here is a preview of what the
warming trend currently looks like. By Sunday, inland temperatures
will gradually warm into the upper 80`s to low 90`s before reaching
into the low to mid 90`s on Monday and low to upper 90`s on Tuesday.
While outside of this forecast period, longer term guidance suggests
that these warmer temperatures will prevail through most of next
week. For those along the coast, temperatures will warm into the
60`s to low 70`s beginning Sunday through the end of the forecast
period.

&&

.AVIATION...
(00Z TAFS)
Issued at 428 PM PDT Tue Jun 25 2024

Satellite shows high-based convection clouds moving across the
region from the south. Therefore, there is a slight chance for dry
thunder and lightening. Conditions will remain VFR through the TAF
period for most terminals with the exception of Monterey Bay
terminal. IFR/MVFR ceilings are expected to return tonight with a
chance KSFO and KOAK may be impacted, but confidence is moderate.
Onshore moderate to breezy winds will diminish tonight to light and
variable before rebuilding to breezy Wednesday afternoon, with a
chance of gusty winds through gaps and passes.

Vicinity of SFO...VFR through the TAF period. As winds diminish
tonight, chances for MVFR/IFR ceilings increase but confidence is
moderate as models show VFR can prevail through the TAF period.
Breezy onshore winds diminish tonight and return to strong and gusty
Wednesday afternoon into the evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR currently. Ceilings lower to IFR
tonight with a chance of low visibility from fog. Clearing is
expected near 15-17Z where winds start to increase to breezy.

&&

.MARINE...
-- Changed Discussion --
(Tonight through next Sunday)
Issued at 840 PM PDT Tue Jun 25 2024

Moderate to breezy northwesterly continue overnight. Stronger
northwesterly breezes arrive into Wednesday morning creating
hazardous conditions for small crafts across all the waters into
the weekend. Significant wave heights will continue to abate
below 10 feet through the period.
-- End Changed Discussion --

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM to 9 PM PDT Wednesday for Mry Bay.

     Small Craft Advisory from 9 AM Wednesday to 3 AM PDT Thursday
     for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-
     10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.

     Small Craft Advisory from 3 PM Wednesday to 3 AM PDT Thursday
     for Pt Arena to Pt Reyes 10-60 NM-Pt Reyes to Pigeon Pt 0-
     10 nm.

     Small Craft Advisory from 9 AM to 9 PM PDT Wednesday for Pigeon
     Pt to Pt Pinos 0-10 nm.

&&

$$

UPDATE...Canepa
SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...SO
MARINE...SO

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