Upcoming Storm, 3/4/19

This is a rather long explanation of what is coming, what is likely, and what is possible, although improbable. From NOAA/NWS:

Early morning satellite imagery shows two features of interest
over the eastern Pacific approaching the California coast. The
first is a comma-shaped cloud mass associated with an upper low
currently centered several hundred miles west of San Francisco
near 35N/145W. The second is an elongated area of cloudiness to
the south of the upper low associated with a plume of subtropical
moisture that is taking aim at south-central California. Models
have been consistent in keeping these two features largely
independent of one another as they approach the coast over the
next 36 hours. What this means is that the subtropical moisture
plume, and its heavy rain potential, will likely remain mostly to
the south of our area. Models generally agree that rainfall
associated with this plume will spread onshore across southern
Monterey County by around midday Tuesday, but then mostly remain
to the south of our area through Wednesday, generating the most
intense rainfall across San Luis Obispo and Santa Barbara
Counties. Meanwhile, the upper low will track towards the northern
California coast and spread widespread rainfall across our area
from late Tuesday into Wednesday. The upper low will entrain
enough moisture to generate moderate rainfall amounts across our
area, and brief locally heavy rain is possible, especially late
Tuesday night and Wednesday morning. Rainfall totals from Tuesday
through Wednesday are currently forecast to range from a half inch
to an inch in most urban/coastal/valley locations, and from 1 to
2 inches in the hills, except up to 3 inches in southwest Monterey
County. Rainfall totals of this magnitude combined with saturated
soil could result in minor nuisance flooding in low lying areas,
but river flooding is not anticipated. Will need to be wary,
however, of any indication that the upper low is entraining more
significant moisture from the moisture plume to its south. If such
a development were to occur, rainfall totals could be
significantly higher across our area, and more widespread and
serious flooding issues could develop. But given the how
consistent the models have been as of late, this more dire
scenario seems unlikely.

From John Lindsey, SLO: “This morning’s  European (#ECMWF) model run is indicating between 2 and 4 inches of rain starting Tuesday afternoon and continuing through Thursday afternoon.”