Early Monday morning forecast (a significant change from last night):
However, the 00Z NAM and now 06Z runs of both the NAM and GFS models indicate the heaviest precipitation will stay offshore as the closed low shifts southward a bit sooner. This greatly lowers forecast confidence given so much discrepancy between the models being only 24 hours out from the onset of more widespread rainfall. Thus, there is the potential for a "forecast bust" if the NAM and 06Z run of the GFS are correct. Now, with this said, the official forecast is more in line with the 00Z run of the GFS, ECMWF and high resolution models. Precipitation is expected to spread inland over the San Francisco Bay Area after midnight and into the early morning hours on Tuesday. The main frontal band will then push across the remainder of the region through sunrise Tuesday and result in widespread rainfall for much of the region. With PWAT values forecast to exceed 1.25" and assuming a more widespread rainfall event, most locations can expect between 0.25" to 0.75" with isolated amounts of more than 1.00" in the favorable west/southwest facing slopes across the region. However, these values could be significantly less if precipitation along the frontal system falls apart or stays offshore.
Late Sunday nite forecast:
While some rain is expected tonight, fellow South Coasters, pay particular attention to this one for Tuesday night. We are in the bull’s eye… in the “…remote and mainly uninhabited areas…” of south western MoCo near the SLO Co line. Okay – Mud Creek’s first test! Note, confidence level is still low to moderate, but keep an eye out.
Models then show upper low offshore tapping into a moisture plume pointed at the Central Coast. Last few nam runs and to some degree the lower resolution global models (gfs,euro) develop a narrow band of heavy rain along the Big Sur coast Tuesday night into Weds morning. Confidence is still low to moderate on these details. Nam model accumulated precip showed nearly a 5 inch accumulated precip bullseye over extreme sw Monterey county near the San Luis Obispo county line. Our local wrf model shows an 8 inch bullseye. This is over remote and mainly uninhabited areas that are usually wet. Have issued a hazardous weather outlook to highlight this potential for locally heavy rainfall. Late Tuesday night into early Weds much of Monterey county