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Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
1245 PM PST Sun Jan 4 2026

...STEADY BAND OF PRECIP MOVING THROUGH CNTRL/SRN CA TODAY ALONG 
WITH T-STORM CHANCES AND SCATTERED SHOWERS ELSEWHERE...
...OFFSHORE LOW EARLY TO MID WEEK TO BRING ADDITIONAL SHOWERS BEFORE 
DRY CONDITIONS RETURN INTO FRIDAY...

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

Moderate to locally heavy band of precipitation is still moving 
across central CA this afternoon from just north of Point Conception 
to I-80. Observations report 1-2.50" over the past 6 hours across 
area mountains and 0.10-0.75" elsewhere. Models again underestimated 
precip over srn CA where a couple gages along the coast are already 
approaching an inch.

Forecast remains on track, the current area of precip will continue 
to move across the region the rest of today sending precip into srn 
CA and the srn/central Sierra into the evening before diminishing 
overnight north of LA county. Precip looks to hang on to the south 
over srn CA into mid morning before diminishing. As this occurs, the 
upper low will be forming west of the nrn CA coast as troughing also 
descends into the region. This will bring another surge of more 
moderate precip into nrn/cntrl CA for Monday. 12z models have the 
low moving further offshore as it heads southward on Tuesday pulling 
most of the precip away from the coast. There is still uncertainty 
as to this, but it is looking more likely as we get closer.

The afternoon update was mainly focused on the next 48 hours with 
the rest of the QPF left un-touched since amounts should be minimal 
with the mid week trough. Blended in the latest WPC guidance/NBM 
along with the 18z HRRR over the next 24 hours. Also made manual 
adjustments to the current period in areas where precip was 
underestimated. This lead to an increase of 0.10-0.75" across 
northern CA over the next couple days and an increase of 0.10-0.50" 
over the San Diego area. The HRRR is putting quite a bit more precip 
over San Diego than any of the other models, but thus far all have 
done a very poor job at picking up on precip developing offshore and 
moving over that area for at least the past week or so. Blended in 
the 18z HRRR a little to bring numbers up, but didn't go as high as 
the HRRR often isn't quite on the nose when it comes to the location 
of heavy convective bands. Did update freezing levels through the 
entire six day window with the 12z models. QPF through 18z Tues: 
0.50-1.50" along the coast (1.50-3.50" coastal mountains), 2.50-4.50 
over Shasta/Sierra, and 0.25-1.25" down the valleys.