SHORT TERM
(This evening through Thursday)
Issued at 140 PM PDT Wed Apr 23 2025

Satellite shows stratus receding across the interior and portions of the coastline. Confidence is mixed on if coastal areas, such as Half Moon Bay and Monterey, and the SF Bay Shoreline will clear today as stratus continues to feed onshore in those places. The current satellite imagery aligns well with HRRR cloud cover guidance which indicated clearing across the interior areas and Santa Cruz Mountains but not for the aforementioned coastal areas and SF Bay Shoreline. The fact that HRRR guidance is in agreement with current satellite observations increases confidence that stratus will persist along most of the coast and the SF Bay shoreline through the rest of today. There is a slight chance clearing will happen during the afternoon but any clearing that does occur along the coast is expected to be short-lived before stratus returns tonight.

We are starting to see temperatures warming up across the interior with temperatures forecast to peak upper 50s to 60s today. The warmest locations (portions of northern Sonoma and Napa counties and interior southern Monterey County) will reach the upper 60s to low 70s. The marine layer is expected to remain at a similar depth (2500- 3000 ft) again tonight as troughing continues to move into the West Coast. This will result in widespread overcast conditions again with fog likely to develop overnight across the valleys. If you encounter fog on your morning commute, remember to slow down and leave extra time to arrive at your destination as sudden decreases in visibility may be possible. Temperatures will cool down a little more heading into Thursday with highs forecast to be in the mid 50s to mid 60s.
Breezy conditions are expected beginning mid to late Thursday morning through early Friday morning. Gusts will generally be between 20 to 30 mph but locally higher gusts between 30-35 mph are possible across elevated terrain (particularly East Bay Hills, Gabilan Range, and Santa Lucia Range). While well below Wind Advisory criteria, it would still be good to secure any loose outdoor decorations tonight before winds pick up tomorrow.

LONG TERM
(Thursday night through next Tuesday)
Issued at 140 PM PDT Wed Apr 23 2025

Thursday night into Friday, upper level troughing will deepen as it continues to move into the West Coast with a cut-off low developing offshore. This cut-off low has continued to shift further south, now moving inland over the Central Coast. An associated surface low and cold front is set to move into the Central Coast overnight Friday into Saturday. As this front approaches, forecast PWAT values increase along the coast of the Central Coast to 0.6"-0.8". The forecasted precipitation totals have increased slightly over the Central Coast with up to 0.5" forecast in the Santa Lucia Range and up to 0.25" across coastal and interior Central Coast. Up to 0.25" is possible across the Santa Cruz Mountains and Santa Clara Hills while the rest of the Bay Area will see up to 0.1".

This approaching system will transport in a cooler airmass which will contribute to an increased risk of thunderstorms across the marine environment and Central Coast Friday to Saturday. A 10-15% chance of thunderstorms exists across the marine environment while a 10% chance of thunderstorms exists throughout the Central Coast and Monterey Bay region. Forecast soundings show a few hundred J/kg of CAPE across the Central Coast overnight Friday into Saturday with forecasted CAPE values to peak Saturday morning. To have a thunderstorm you need four main ingredients: moisture, instability, lift, and wind shear (speed or directional). With this system incoming, we have a source of moisture, a source of lift (cold frontal passage), and some instability forecast. The questionable ingredient is wind shear. As of right now during the time of the highest thunderstorm probabilities (5AM-5PM Saturday), forecast soundings show some directional wind shear (winds veering with height indicating some warm air advection is occurring) but not very much speed wind shear. The surface to 500 mb bulk shear shows much higher speed shear values located just to our south in San Luis Obispo County (NWS Los Angeles' CWA). While the current trend for this cut-off low has been to shift southwards, if the low were to shift just slightly northward we could potentially see those higher bulk speed shear values shift into Monterey County. If this were to occur, it would increase confidence that we may see some thunderstorms across southern Monterey County given the alignment of wind shear with our area of moisture, lift, and instability. It's worth watching over the next few days to see where this cut-off low tracks (further south or further north) and how our thunderstorm risk along the Central Coast changes this weekend.

Cooler temperatures in the 50s to low 60s will persist through Sunday before upper level ridging moves back in on Monday. This will kick start a warming trend back to more seasonal temperatures with inland temperatures rising into the 70s and coastal temperatures into the low to mid 60s. Minor HeatRisk, primarily impacting those who are extremely sensitive to heat, is forecast to return to the Bay Area and Central Coast on Monday and Tuesday next week. Long range guidance indicates upper level ridging is likely to persist in the longer term with the CPC outlook showing above normal temperatures and below normal precipitation for the month of May.
The rainy season in California typically goes through the end of April with the dry season beginning in May. Our incoming Friday- Saturday system is likely to be one of our last systems of the rainy season before dry summer weather returns.

AVIATION
(18Z TAFS)
Issued at 1029 AM PDT Wed Apr 23 2025

Currently a mixed bag of VFR-MVFR across the board with stratus beginning to dissipate. Bayside and coastal terminals can expect to remain MVFR through the TAF period with low confidence on VFR ever being achieved. High confidence on low-end MVFR ceilings returning to all terminals tonight, lowest confidence on STS and whether fog or stratus will win out.

Vicinity of SFO...Currently MVFR with westerly flow. Ceilings may briefly lift to VFR this afternoon, but confidence is low to moderate on that happening. The most likely scenario is that MVFR conditions and moderate westerly winds will prevail through the TAF period.

SFO Bridge Approach...Low clouds will linger along the San Mateo Bridge Approach, particularly across the San Francisco Bay from SFO to OAK.

Monterey Bay Terminals...Currently MVFR with westerly flow at both terminals. Moderate confidence on a brief period of VFR for SNS this afternoon, otherwise MVFR conditions and moderate westerly winds will prevail through the TAF period for both terminals.

MARINE
(Today through Monday)
Issued at 904 AM PDT Wed Apr 23 2025

Strong northwesterly breezes and rough seas can be expected for the outer waters today. Conditions improve tomorrow with light rain chances Friday into Saturday. Strong northwesterly breezes and rough seas return Saturday afternoon.

MTR WATCHES/WARNINGS/ADVISORIES
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Thursday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm.

Small Craft Advisory until 3 AM PDT Thursday for Pt Pinos to Pt Piedras Blancas 0-10 nm.

Small Craft Advisory until 3 PM PDT Thursday for Pt Arena to Pt Reyes 10-60 NM.