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Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
730 AM PST Tue Feb 17 2026

...A SERIES OF LOWS TO MOVE IN FROM THE NORTHWEST THROUGHOUT THE 
WEEK BRINGING PERIODS OF WIDESPREAD PRECIP AND OCCASIONAL T-STORMS...

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

The moisture plume affecting southern CA yesterday has left the 
region. TPW imagery shows about 0.50-0.75" of PW remaining as 
yesterday's trough has been absorbed into the larger flow regime. 
Totals over the past 24 hours are most notable across the Big Sur 
coast, Transverse Range, and Sierra where 2-4" of precip have been 
reported. Another upper low is approaching from the northwest now 
located just offshore of the PacNW. Troughing from this low has 
already descended into nrn/central CA with a cold front across nw CA 
through the Cascades and a weakening front still over srn CA. This 
is generating scattered showers across the region, mainly over 
nrn/central CA but there were some more moderate showers moving 
through San Diego county earlier this morning. Current radar has 
developing areas of thunderstorm activity around the I-80/I-5 
junction with an area of 40-50 dbZ echos and several lightning 
flashes both over land and just offshore. Scattered showers and 
thunderstorms will continue the rest of today as the system drops 
further into CA while opening into a trough. HREF exceedance 
probabilities show 10-40% chances of exceeding 0.50"/hr rain rates 
increasing along the Big Sur coast in the afternoon and the western 
Transverse Range in the evening as the system moves southward. 
Embedded rates of 1"/hr hour possible as well at about 10%. Some 
terrain enhanced precip over the Transverse and southern Sierra are 
expected again this evening and overnight, though low level winds do 
not look directly south this time so not expecting the kind of 
numbers you'd see in an AR with southerly flow given both of those 
components will be absent. 

Over the next 24 hours expecting another 2-5" across the Sierra and 
1-3.50" over the Big Sur/Transverse/San Jacinto mountains. Freezing 
levels should remain lower at 2.5-5.5 kft north of Point Conception 
before lowering again tonight as that next trough moves in.

Wednesday, the trough will swing inland beginning to exit into the 
Four Corners in the afternoon. This should allow precip across 
central and southern CA to diminish into lighter scattered showers. 
Later Wednesday, another system is progged to drop in from the 
northwest sending an additional surge of precip into nrn CA. This 
arrives as a relatively weak surface low and upper trough. The main 
band of precip around the surface low is expected some time in the 
evening. The GFS and ECMWF are in some disagreement on the 
positioning with this feature. The ECMWF is further east and the GFS 
further west keeping heavier showers just offshore overnight. This 
is a point of uncertainty in the QPF for Wednesday. With this system 
chances of thunderstorms again this time along the coast from 
Monterey northward. Thursday the entire system will start to shift 
east pushing that surface low inland as the trough moves through. 
This will bring more showers across central and then southern CA 
through Thursday along with thunderstorms over much of nrn/central 
CA. That system looks to exit Thursday night and Friday morning with 
some brief drying behind it on Friday as weak ridging develops in 
between systems. 

More widespread precip is then on tap as another larger 
surface/upper low approach again from the Gulf of Alaska. Models 
overnight have slowed down the arrival of this next system, so QPF 
was pared back compared to yesterday. However, models do disagree on 
when exactly showers will move in. The det models are slower 
compared to the ensembles. The det GFS and ECMWF bring showers in 
Saturday evening while the ensembles range anywhere from Friday 
evening to Monday. The NBM is on the earlier side taking light 
showers into the north coast Friday evening. The official forecast 
was mainly the NBM though trimmed the extent for Saturday to the 50% 
to slow down the precip. The system should be spreading precip 
across the region on Sunday into Monday, though the speed of this is 
another source of uncertainty. For now, elected to keep precip 
mainly north of Point Conception through Sunday night.

Precip amounts from Wednesday onward should be highest along the 
north coast/Shasta/northern Sierra and over the central coast 
mountains. QPF 12z Weds-12z Mon: 3-5.50" nrn CA coast Mendocino 
county northward (up to 7" King Range)/Shasta, 2.50-5" nrn Sierra, 
1.50-3" central/srn Sierra, 1.50-4" central coast mountains, 1-2.50" 
most of the greater Bay Area and nrn Sac Valley, 0.25-1.25" SJ 
valley into the foothills, and 0.50-1" coastal srn CA (1-2.50" San 
Gabriel/San Bernadino/San Jacinto/Laguna mountains). 

Freezing levels relatively low most of the week as these are colder 
systems. Levels forecast at about 2.5-5.5 kft for most areas rising 
into the weekend from sw to ne to 4-6.5 kft from I-80 to the 
southern Sierra early Saturday. Further increases expected by the 
evening 6.5-9 kft for those areas and 7-9.5 kft across the Sierra by 
Sunday evening.


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.