Weather Report from NOAA

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