UPDATE
Issued at 823 PM PDT Sat Sep 7 2024

Temperatures across our area did cool slightly from yesterdays highs across our area, mostly around 2 to 5 degrees, with that trend continuing through the middle of next week. Many spots that are in the 90s to low 100s today will be 20 to 25 degrees cooler by Wednesday afternoon.

Low marine stratus is a little slower working south from the Bay Area to Monterey Bay this evening but will eventually impact most of our coastal locations with low ceilings, patchy to dense fog at times and light drizzle through the remainder of the overnight hours into Sunday morning.

SHORT TERM
Issued at 112 PM PDT Sat Sep 7 2024 (This evening through Sunday)

A ripple through the longwave pattern over the West Coast this afternoon thanks to an upper low sweep eastward through N CA/S OR.
While this feature is bringing showers and thunderstorms up north it's resulted in sunny, but cooler conditions across the Bay Area and Central Coast. Afternoon visible satellite shows marine layer stratus hugging the coast, but inland sunshine. Latest 24 hour trends shows many locations running similar to or colder than 24 hours ago. Despite the "cooldown" there are still many locations well above 90 degrees. One notable place is the Big Sur RAWS sitting at 98 degrees. Pretty impressive given the proximity to the coast. Definitely has a shot at eclipsing 100 degrees. Other far interior locations away from the coast range from 95-105 degrees. These locations have a moderate HeatRisk, but coverage isn't widespread enough to warrant another Heat Advisory.

Fire Weather concerns continues this afternoon as well. Area of greatest concern are the interior N Bay Mts. Last night featured no humidity recovery with places lingering in the single digits for RH. The same is true this afternoon with places holding steady below 10%. Winds are breezy with gusts up to 15 mph. Bone dry conditions with some wind will result in elevated fire weather conditions.

Tonight and Sunday: Marine layer along the coast will gradually move in. Similar to this morning, fog will once again be possible.
Only subtle changes in the overall sensible weather on Sunday.
Coastal clouds with inland sunshine - repeat from Saturday.
Pockets of 100+ deg possible over interior Monterey/San Benito.

LONG TERM
Issued at 130 PM PDT Sat Sep 7 2024 (Sunday night through next Friday)

Additional, but weaker, ripples roll through the upper level pattern through early next week. The lower 500mb heights and cooling airmass will allow for additional cooling both day and night. Onshore flow will persist, which will lead to a deepening of the marine layer and increasing night/morning low clouds. Have added coastal drizzle to the forecast (late night/early morning)
through this timeframe as well.

A more pronounced upper level trough develops by Tuesday night/Wednesday over the PacNW. Given all of the wildfire over OR a lot of hope was riding on this system being wetter, but sadly recent trends are drier. As for our area, some drizzle is possible, but looking more inside slider-ish for Wednesday/Thursday. Temperatures remain cooler on Wednesday/Thursday, but more importantly winds begin to shift with an offshore component. At this point it doens't appear to be a big offshore setup, but something we'll be watching nonetheless.

AVIATION
(06Z TAFS)
Issued at 1112 PM PDT Sat Sep 7 2024

Stratus is filling in along the coastline and starting to push inland. IFR to LIFR CIGs are expected overnight with elevated fog potential across the North Bay and Central Coast. Stratus may remain patchy into the early morning before filling in more consistently around 10-12Z. Stratus is expected to clear by mid to late morning with an early return of stratus possible in the mid to late evening.
Aside from the North Bay where winds are more southerly to southwesterly, winds generally stay out of the northwest. Winds are expected to weaken at all stations overnight before strengthening and becoming moderate again tomorrow afternoon/evening.

Vicinity of SFO...Night fog shows stratus moving through the San Bruno gap with few to scattered low level clouds currently reaching SFO. Stratus is expected to fill in more consistently around 08Z as stratus pushes inland. IFR CIGs are currently expected but given the current observations showing few clouds around 300 ft cannot fully rule out the possibility of LIFR CIGs developing later tonight. The RAP and HRRR both suggest 8-10Z as the most likely time for stratus arrival. Any stratus that does develop will persist through late tomorrow morning with VFR expected to continue through the afternoon/evening. Winds generally stay out of the west to northwest with breezier conditions and gusts up to 25 knots possible during the day.

SFO Bridge Approach...Similar to SFO but stratus may take longer to fill in over the bay compared to at SFO which may allow VFR conditions to persist for longer overnight on the approach compared to at the airport.

Monterey Bay Terminals...Stratus is currently filling in over the Monterey Bay Region with LIFR CIGs to reach MRY and SNS early this morning. An otter eddy looks to be developing which may keep stratus coverage patchy for the next few hours before stratus moves in more consistently. Similar to the last few nights, elevated fog potential continues with visibilities down to 1/2SM possible after stratus moves in. Winds generally stay out of the northwest but weak offshore flow may develop overnight as winds become more light and variable. Winds strengthen and become more moderate during the day at SNS but are expected to stay fairly light through the TAF period at MRY.

MARINE
(Tonight through next Friday)
Issued at 1112 PM PDT Sat Sep 7 2024

Moderate to breezy north and northwest winds continue through the weekend with occasional gusty winds over the southern waters.
Northwest winds strengthen and wave heights increase over the California coastal waters ahead of an incoming low pressure system by the middle of next week with unsettled conditions persisting through the end of the week.

MTR WATCHES/WARNINGS/ADVISORIES
CA...None.
PZ...None.