313
AGUS76 KRSA 172042
HMDRSA

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
1240 PM PST Mon Nov 17 2025

...WIDESPREAD PRECIP AND POSSIBLE T-STORMS THE REST OF TODAY ACROSS
CA AS AN UPPER LOW MOVES THROUGH...
...LINGERING SHOWERS AND T-STORMS OVER SRN CA TUES, THEN A SECOND
UPPER LOW TO RETURN PRECIP CHANCES TO THE REGION MID TO LATE WEEK...

.METEOROLOGICAL CONDITIONS (MON PM - SUN AM)...

A low continues to travel along the coast rotating precipitation
into CA this afternoon. Lightning detection is picking up some
flashes in the SJ Valley as radar shows scattered areas of
precipitation across much of the state. Heaviest areas right now are
focused over coastal srn CA, specifically Santa Barbara/Ventura
counties right around the cold front and a narrow plume 1"+ PW of
moisture. HREF exceedance probabilities show a 40-75% chance of
0.50+"/hr rain rates over that area the rest of the afternoon and
isolated areas across the state at a 10-30% chance. Rain rates
should then begin to diminish later this afternoon into this
evening. Models have the low continuing to move south along the
coast the rest of today and tomorrow resulting in additional
scattered showers and thunderstorms before moving inland around srn
CA/Baja on Wednesday. Relatively minimal changes in QPF from this
morning around 0.10-0.50" up or down from 18z today to 00z Thurs for
the current system. Expecting another 0.50-1.50" or so for coastal
srn CA, 0.75-2" for the southern Sierra, 0.25-0.75" for the central
coast mountains, and generally 0.10-0.50" elsewhere. Locally higher
under thunderstorms. It is also possible that precip will exceed the
forecast again over the western Transverse.

For the rest of the forecast period, another upper low is still set
to approach from the nw on Wednesday traveling south offshore of
the CA coast the rest of the week then heading inland late this
weekend through srn CA/Baja. The same points of disagreement remain
on timing and the trajectory of the system, but the models have come
a little closer together in the 12z runs. Still a good deal of
uncertainty due to that disagreement and ensemble spread. 48 hr QPF
clusters ending Saturday morning show anywhere from less than 0.25"
to 2" over coastal srn CA and over 5" across the Transverse on the
higher end. Ensemble members from each det parent are pretty well
spread out across the 4 clusters so this is more than just basic det
model disagreement. The amount of precip will largely depend on how
close the low is to the coast as it moves south and when it decides
to take a turn and head inland. Bottom line, a wet pattern looks to
continue for the rest of the week and into the weekend. Changes from
this morning`s forecast include an increase of 0.10-0.50" or so
along the srn CA coast and generally 0.10-0.25" changes elsewhere
along the coast. QPF 00z Thurs to 12z Sun: 0.75-1.50" coastal srn
CA, 0.25-0.75" rest of the CA coast, and 0.10-0.50" for most of the
rest of CA.



QPF graphics are available at www.cnrfc.noaa.gov/qpf.php



AS

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