textproduct: San Francisco Bay Area

SYNOPSIS

Issued at 1243 PM PDT Wed Apr 2 2025

Warming and drying trend begins today with temperatures above seasonal averages by Friday. A weak cold front is possible later this upcoming weekend.

SHORT TERM

(This evening through Thursday) Issued at 1243 PM PDT Wed Apr 2 2025

Fair weather cumulus clouds are popping off across the region as the upper level low and surface trough that gave us the last two days of convective showers continues to move towards the southeast. Today marks the start of a warming and drying trend that will begin rather modestly, with high temperatures today reaching the lower to middle 60s in the inland valleys, the middle 50s to near 60 in the coastal areas, and the 40s to the lower 50s in the higher elevations. Gusty post-trough winds will develop this afternoon and evening, with gusts reaching 25 to 30 mph along the coast, through the gaps and passes, along the ridgelines, and within the northern Salinas Valley.

Tonight, clear skies and calmer winds will enhance radiational cooling, with low temperatures expected to be chilly across the region. A Frost Advisory has been issued for the North Bay valleys and the interior Central Coast, including the southern Salinas Valley, from 2 AM to 9 AM Thursday morning. Lows in these areas will reach the middle to upper 30s, with the coldest spots across the interior Central Coast reaching the lower 30s. These are borderline as far as the Frost Advisory criteria, especially in the North Bay, but the start of the budding season means that agricultural interests are currently extremely sensitive to low temperatures, which tipped the scales toward issuing the Frost Advisory. Elsewhere, lows will range from the upper 30s inland to the middle to upper 40s along the coast. Three long-term climate sites continue to see forecasts threatening daily minimum temperature records: San Rafael, where a forecast of 42 compares to a record of 39 degrees from 2010; downtown San Francisco, where a forecast of 44 degrees compares to a record of 41 degrees from 2001; and the Oakland Museum, where a forecast of 44 degrees compares to a record of 43 degrees from 2003. High temperatures will feel slightly warmer on Thursday with most regions seeing highs around 3 degrees warmer than today's highs, give or take a couple of degrees.

LONG TERM

(Thursday night through next Tuesday) Issued at 1243 PM PDT Wed Apr 2 2025

The warming and drying trend continues through the week as an upper level ridge builds across the West Coast. This upcoming weekend, highs should reach the middle 70s to near 80 across the inland valleys. For context, this is around 5 to 10 degrees above the seasonal average, and Minor HeatRisk could return to the inland valleys, meaning that there is a low risk for heat related illnesses among people extremely sensitive to heat, especially those without effective cooling and.or adequate hydration.

On Sunday and Monday, a cold front will skirt the Bay Area, bringing an interruption to the warming trend and a chance for light rain. Confidence is increasing in the chances for rain in the Bay Area, especially across the North Bay. However, the rainfall totals are yet to come into better focus. As before, potential rainfall totals continue to be modulated by the exact location of the cold front and how it interacts with a upper level ridge over the western United States. That said, even the most optimistic forecasts top out around a half to three quarters of an inch across the Sonoma County mountains, and every forecast agrees with progressively lower rainfall totals the farther south you go. Stay tuned to the forecast as the details evolve.

The warming trend resumes after the cold front moves out, with high temperatures continuing to climb into the lower to middle 80s by mid- week.

AVIATION

(06Z TAFS) Issued at 1039 PM PDT Wed Apr 2 2025

Patchy MVFR CIGs along the coastline and Monterey Bay region with highest confidence in MVFR CIGs continuing to impact HAF and MRY. NBM is best representing the current satellite setup which shows cloud cover across the South Bay and interior Monterey County diminishing, decreasing confidence that CIGs will reach SJC or SNS. Some potential for fog during the early morning hours at STS and APC but confidence is low with local WRF guidance suggesting conditions will be on the drier end. Gusty onshore flow continues at OAK, SFO, and HAF but has diminished from earlier this afternoon. Winds continue to diminish overnight before widespread moderate onshore flow returns during the day tomorrow.

Vicinity of SFO...VFR. Patchy MVFR CIGs are possible overnight but confidence is low. HREF and NBM guidance keep CIGs more directly along the coastline which should keep CIGs away from SFO. Gusty onshore flow will continue to diminish overnight before moderate west to northwest winds return during the day tomorrow.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Borderline VFR/MVFR conditions at MRY overnight, VFR at SNS. Low clouds continue in the vicinity of MRY with BKN CIGs hovering on the BKN030-035 border. Current thinking is CIGs will hover closer to BKN030 with temporary decreases to between BKN025-030 possible. CIGs look to remain slightly higher at SNS where VFR conditions persist through the TAF period. Onshore flow will continue to diminish overnight with moderate west to northwest winds expected during the day tomorrow.

MTR WATCHES/WARNINGS/ADVISORIES

CA...Frost Advisory from 2 AM to 9 AM PDT Thursday for CAZ506-516>518.

PZ...Small Craft Advisory until 3 AM PDT Thursday for Pigeon Pt to Pt Pinos 0-10 nm-Pt Arena to Pt Reyes 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

Small Craft Advisory until 3 AM PDT Friday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm.