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Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
750 AM PDT Wed Apr 8 2026

...A PAIR OF UPPER LOWS WILL BRING WIDESPREAD PRECIP TO THE REGION 
LATER TODAY THROUGH THE WEEKEND...
...T-STORMS POSSIBLE OVER NRN/CNTRL CA/NV IN THE AFT/EVE THE NEXT 
FEW DAYS...

.METEOROLOGICAL CONDITIONS (WED AM - TUE AM)...

An upper low sits just west of 130W offshore of nrn CA early this 
morning as a detatched area of 1-1.25" PW moisture has reached the 
nrn/cntrl CA coasts. Radar imagery shows some light returns moving 
into the North Bay with additional echos west of Cape Mendocino 
ahead of the main system. Expecting initial shower activity over nrn 
CA by this afternoon along with chances of thunderstorms. The low 
will continue to creep closer to the coast Thursday sending some 
more moderate precip into nw CA as troughing moves inland. The low 
looks to remain offshore of nrn CA near Cape Mendocino throughout 
Thursday and into Friday as well, gradually opening up into a trough 
as its surface low deteriorates. This troughing and a weakening 
front will spread showers further across the state Thursday night 
into Friday morning spreading past Point Conception and into the 
southern Sierra in the afternoon. Thunderstorms remain possible for 
Thursday and Friday mainly east of the Delta and north of the 
Monterey Peninsula spreading a bit further across CA/NV on Friday as 
the trough pushes inland.

As this first system weakens, another will drop in from the Gulf of 
Alaska reaching the north coast Saturday morning. The arrival of 
this system and the continued presence of the weakening trough will 
keep shower activity going across much of the region as we 
transition between systems. A push of more moderate precip from the 
second system is anticipated Saturday morning first over nw CA and 
then spreading into the nrn/central Sierra in the afternoon as the 
low takes a more direct path inland. There is some disagreement on 
Sunday between the GFS and the ECMWF on the overall pattern, but 
continued shower activity is forecast through the weekend with 
intensity diminishing throughout. Monday, expect precip to wind down 
with showers over the Sierra and NV persisting as the system exits 
to the east.

There is uncertainty in the forecast due to ensemble spread, though 
there is general agreement that the bulk of the precip is expected 
over nw CA, Shasta, and the nrn/cntrl Sierra. Looking at ensemble 
QPF clusters, 30% of both the GEFS and ECMWF ensemble members show 
pockets of the Sierra getting over 5" through Saturday afternoon 
while peaks in the others are closer to 1.50-3". Disagreement over 
nw CA as well with totals varying from 0.75" to nearly 2". Similar 
issues from 00z Sat to 00z Mon, though this time 44% of the 
ensembles favor heavier precip over the Sierra while the rest 
disagree more strongly on the precip over nw CA. Cluster 3 which has 
21% of the overall membership shows very little precip while 
clusters 1 and 2 are showing 0.50-1.50". All this to say, relatively 
confident that a pair of lows will bring widespread precip to the 
region starting later today and lasting through the weekend though 
lower confidence on amounts.

In addition to precipitation, this pattern shift will usher in 
cooler air bringing afternoon high temperature anomalies down from 
+5 to +15 deg F today and tomorrow down to near to below normal 
Friday. Temperatures will bottom out on Sunday with anomalies at -5 
to -15 deg F.

QPF this morning was a blend of the morning WPC guidance and the 
latest NBM. This brought totals down about 0.50-1" over srn CA and 
up 0.25-1" over nrn CA (even higher across the Sierra). Amounts 
likely will change over terrain areas in the coming days as models 
dial in better on the exact positioning of the lows and the 
subsequent orographics. QPF for the first system (through 12z Sat): 
0.50-1.75" nw CA/Shasta/Sierra and 0.10-0.75" for the rest of the 
region aside from SE CA where little to no precip is expected. QPF 
for the second system (12z Sat - 12z Tues): 1-1.50" nw CA, 1-3" 
Shasta, 1.50-3.75" Sierra, 0.50-1" central coast/Bay Area (up to 
1.50" Santa Cruz and Big Sur mountains), 0.10-0.75" coastal srn CA, 
and 0.30-1" down the valleys.

Freezing levels 9-12.5 kft later today into tonight lowering Friday 
afternoon to 7.5-9 kft north of I-80 and up to 10.5 kft for parts of 
the srn Sierra. As the second low moves inland, freezing levels will 
continue to drop over the weekend reaching a min early Sunday of 4.5-
7 kft across the Sierra before lower levels spread into Monday of 
4.5-6 kft. As the system exits into Tuesday, expect freezing levels 
to quickly rebound from west to east back up to 6.5 kft from the NV 
border to 9.5 kft at the central coast.


Please Note: This product may NOT be routinely updated.
Please refer to the following product issued by the CNRFC
www.cnrfc.noaa.gov/Daily-Briefing for a graphical summary of
weather and hydrologic conditions.