SHORT TERM
(This evening through Sunday)
Issued at 152 PM PDT Sat Oct 5 2024

Widespread Moderate to Major HeatRisk continue across the region this afternoon with isolated Extreme HeatRisk in higher elevations.
However, a very shallow marine layer continues to keep areas closest to the coast cooler. This makes forecasting for the coast extremely challenging! That said, have extended all heat products out to 11 PM Sunday with the exception of San Francisco which may be allowed to downgrade to a Heat Advisory for tomorrow. Current radar and satellite are showing some returns of elevated showers over the waters and well southwest of the Monterey Bay region, courtesy of some lingering subtropical moisture around 10,000 feet. However, this is unlikely to reach the surface with conditions extremely dry above the marine inversion.

Tonight, temperatures are expected to stay very warm in the region's higher elevations with 70's to mid 80's expected while the valleys and coastal areas cool into the low-to-upper 60's with pockets reaching as low as the mid 50's.

Tomorrow will be equally as hot as today with slight cooling likely near the coast as the marine layer is forecast to increase slightly.
Thus, expecting more widespread triple digit heat across the interior, 90's in the Bay Shoreline and other inland portions of the region, and 70's to 80's near the immediate coastline.

A few interesting climate stats:

* If San Jose Airport hits 100 today, it will be the most days with a high of at least 100 in a calendar year on record. Currently tied the record, which is 5 days at or above 100 (occurred in several past years).

* Santa Rosa Co-op station has broken the record for the most days above 100 in a calendar year with 12 days so far. Old record was 11 days in 1976 and 1917.

* San Rafael has broken the record for most days above 100 in a calendar year with 11 days so far (including today). Old record was 8 days in 1976.

LONG TERM
(Sunday through Friday)
Issued at 151 AM PDT Sat Oct 5 2024

The onshore flow paired with falling 500 mb heights will be the beginning of the end of this heatwave. By Monday morning, strong northwest winds develop in a coastal jet ahead of an approaching upper level trough. The marine layer is expected to deepen into Tuesday, bringing much welcome relief across a much broader swath of the region. For the latter half of the week, guidance continues to advertise a deep trough swinging into the PNW and grazing northern and central California. Ultimately, this would bring some sense of rainfall to the region, but don't hold your breath.
While ensemble members have been consistent with showing this, they've also been consistent in that not very many members are on board. Therefore, the chance still remains very low that we see measurable rain by the end of next week in the North Bay.

AVIATION
(00Z TAFS)
Issued at 440 PM PDT Sat Oct 5 2024

Dry airmass and offshore flow at times will lead to VFR for most terminals through the TAF period. As noted on the previous TAF package, Monterey Bay terminals will be the challenge. Southerly surge battling northerly/offshore flow has kept clouds in Monterey Bay. Once the sun sets local level flow may be enough for clouds to sneak inland. Have higher confidence for low cigs at KSNS than KMRY. Additionally, this onshore push would be shallow yielding dense fog.

Vicinity of SFO...VFR.

SFO Bridge Approach...VFR.

Monterey Bay Terminals...SCT002 KMRY. Low cigs/fog will lurk nearby for KMRY. Have CIGS and FOG moving into KSNS late tonight.
Clearing will be mid morning Sunday.

MARINE
(Today through Thursday)
Issued at 235 PM PDT Sat Oct 5 2024

High pressure located over land continues to produce light to moderate northerly flow over the coastal waters, which will persist through Monday. High pressure will re-strengthen over the Eastern Pacific on Monday, which will increase winds over the waters. As hot conditions persist and people flock to the coast, always remember to wear a life jacket, swim near a lifeguard, and never turn your back on the ocean.

CLIMATE
Issued at 906 PM PDT Fri Oct 4 2024

Record high temperatures and years of occurrence at the long term climate stations October 5 and 6.

Station Oct 5 Oct 6

Santa Rosa 103 1933 102 1930 Kentfield 100 1987 97 1930 Napa 101 1987 96 1930 Richmond 99 1987 91 1996 Livermore 100 1980 100 2014 San Francisco 102 1987 94 1992 SFO Airport 99 1987 92 2023 Redwood City 99 1987 99 1987 Half Moon Bay 90 2023 87 1972 Oakland museum 96 1987 93 2023 San Jose 101 1987 95 2023 Salinas Airport 105 1987 98 2023 King City 105 1933 100 1996

MTR WATCHES/WARNINGS/ADVISORIES
CA...Excessive Heat Warning until 11 PM PDT this evening for CAZ006.

Excessive Heat Warning until 11 PM PDT Sunday for CAZ502>504-508- 510-512>518.

Heat Advisory until 11 PM PDT Sunday for CAZ506-509-528>530.

PZ...None.