306
FXUS66 KMTR 260528
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1028 PM PDT Tue Jun 25 2024

...New AVIATION, MARINE...

.SYNOPSIS...
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.

&&

.UPDATE...
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.

&&

.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...
(06Z TAFS)
Issued at 1027 PM PDT Tue Jun 25 2024

The low chance-high impact threat for high-based convection has
ceased. Currently VFR at all terminals except the Monterey Bay
terminals of MRY and SNS. VFR through the TAF period for APC, LVK,
SJC, and STS. Overnight the Bay Area terminals of OAK and SFO will
deteriorate to low-end MVFR. Winds will remain onshore through the
TAF period.

Vicinity of SFO...Currently VFR with westerly flow. Winds will
prevail out of the west through the TAF period. A low-end MVFR
ceiling will impact the terminal overnight and scatter out by mid-
morning.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Currently IFR with westerly flow at MRY and
IFR with northwesterly flow at SNS. Winds will prevail out of the
west/northwest through the TAF period. VFR will prevail by tomorrow
afternoon with IFR stratus making an early return to the terminals
tomorrow evening.

&&

.MARINE...
(Tonight through next Monday)
Issued at 1027 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.

&&

.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 PM 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 PM 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.

&&

$$

SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...Sarment
MARINE...SO

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