, Issued at 1111 PM PDT Tue Apr 7 2026 (Tonight through Wednesday night)
Wednesday's weather is brought to you by upper-level shortwave ridging. The aforementioned ridge's axis across the state and a cutoff low right behind it is supporting onshore flow. A modest marine layer of 1,500 feet was observed on the 00Z April 8th sounding - this may actually undergo some deepening tonight as heights ever so slightly begin to fall ahead of the approaching cutoff low. Nonetheless, a cloudy start can be expected along the coast and in the valleys with temperatures warming to 5-10 degrees above normal by the afternoon.
..issued at 1111 PM PDT Tue Apr 7 2026 (Thursday through next Tuesday)
The aforementioned cutoff low near 38 N, -138 W in the Eastern Pacific Ocean will kickoff our pattern change on Thursday. Due to its independence from the jet stream, its exact location and timing is difficult to say with certainty. Thus, this is a boom or bust forecast by nature which is evident in the spread between the 10th and 90th percentiles. For example, 72-hour accumulation for Santa Rosa between now and 5 PM Friday is forecast to be 0.22" with a 10th percentile of 0.03" and a 90th percentile of 0.40". No matter how you slice it, it's not a lot of rain; however, this provides insight that rainfall totals will be highly dependent on where rain showers/thunderstorms develop. The trend has been for an even slower progression of the surface low to the east. While rain and thunderstorms on Thursday cannot be completely ruled out with the outer rain bands, the best thunderstorm chances are now expanding from Friday into Sunday. Point forecast soundings illustrate that the profile will be characterized by conditionally unstable lapse rates yielding low CAPE, high 0-6 km shear, and PWAT values near the 90th percentile. It also shows that thunderstorms will likely be diurnally driven by surface heating with the most unstable parcel being the surface parcel. Thunderstorm hazards include lightning, locally heavy rainfall, erratic/gusty winds, and small hail. Due to the slow steering motion and training effect of cutoff lows, localized flooding will be possible if a rain shower/thunderstorm were to develop. There is high confidence that the cutoff low gets absorbed with the help of a digging upper-level longwave trough from the Gulf of Alaska late Friday, but global ensemble clusters diverge by Saturday on the depth, strength, and type of troughing across the state. Deterministic ECMWF and GFS are both advertising a surface low digging down the West Coast and cutting inland in Northern California. The close proximity to the low would maintain rain and thunderstorm chances over the weekend. Rainfall totals on the order of 0.50"-1.00" are expected with up to 2.00" in the coastal ranges. Heights will begin to rise Monday, kicking off at least a brief warming and drying trend.
(12z TAFS) Issued at 421 AM PDT Wed Apr 8 2026
Areas of coastal stratus /MVFR-IFR/ continue to form and winds are light onshore. The highest probability of VFR will be inland today. Coastal stratus /MVFR-IFR/ increases and moves inland tonight and Thursday morning.
Vicinity of SFO, VFR. West wind near 10 knots increasing to 15 knots in late morning and afternoon. West wind 10 knots tonight and Thursday morning.
SFO Bridge Approach, Similar to SFO.
Monterey Bay Terminals, Stratus /MVFR-IFR/ until late morning then VFR for the afternoon. Stratus /MVFR-IFR/ redevelops and moves inland tonight and Thursday morning. Mainly onshore winds 5 to 15 knots.
(today through Monday) Issued at 412 AM PDT Wed Apr 8 2026
Winds will shift to southwest today through Thursday ahead of a low pressure system. This system will merge with another low pressure system arriving from the northwest and result in showers and a chance of thunderstorms Friday through Sunday. A cold front with the newly arriving system will move across the coastal waters and bays Saturday and Saturday night. Northwest winds will develop behind the cold front late in the weekend.
Ca, None. PZ, None.
