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Hydrometeorological Discussion
National Weather Service / California-Nevada RFC / Sacramento CA
650 AM PDT Fri Oct 16 2026

...WARMER AND MAINLY DRY CONDITIONS THROUGH THE WEEKEND...
...COOLING NEXT WEEK AND INCREASING PRECIP CHANCES AS A LOW MOVES 
THROUGH...

.METEOROLOGICAL CONDITIONS (FRI AM - THU AM)...

An upper low remains just offshore of srn CA this morning embedded 
in a broad upper ridge stretched across most of the west coast. The 
main result is dry offshore winds across srn CA and widespread above 
normal temperatures region wide. The offshore low may, however, drag 
enough tropical moisture into se CA to cause a couple of showers 
this afternoon and tomorrow afternoon. Potential for isolated 
thunderstorms over se CA tomorrow afternoon as well. Otherwise, dry 
conditions are expected through the weekend along with temperature 
anomalies of +5 to +20 deg F. The ridge overhead will drift 
eastward, gradually being replaced by troughing from the northwest 
before a low embedded in that flow pattern approaches on Sunday. 
This will usher in some cooling by early next week. Widespread below 
normal temperatures anticipated Tuesday onward. 

Earlier model runs tracking this low had it going through nrn CA 
Monday/Tuesday, but have since evolved to predict an offshore cutoff 
low that will at some point make its way through srn CA next week. 
How closely the low sticks to the coast as it heads southward will 
determine how much if any precip falls over nrn/central CA Monday. 
Right now, things look fairly light at a 0.10" or less along the 
north coast into Shasta and down across the Bay Area with chances of 
showers increasing and becoming more widespread late 
Tuesday/Wednesday as the low reaches Point Conception. The GFS and 
the ECMWF have the low moving inland across srn CA into Thursday 
with most of the precip focused over coastal srn CA, the Sierra, and 
srn NV. Amounts are still uncertain as ensemble spread remains high. 
Looking at the 24 hr QPF ensembles at LAX, members have anything 
between 0" and 2" for Wednesday into Thursday.

The official forecast was generally a blend of WPC guidance, the 
NBM, and the ECMWF. Expect amounts to change over the coming days, 
any shift in either direction of that low could significantly impact 
the QPF. Majority of the precip is expected Tuesday/Wednesday. QPF 
12z Mon to 12z Thurs: 0.50-1" coastal srn CA (up to 1.50" Transverse 
Range), 0.25-1" Sierra/srn NV, 0.10-0.50" central coast, and 
generally 0.10" or less for the rest of nrn and central CA.

Freezing levels starting at about 13-15.5 kft today gradually 
lowering into early next week down to 8.5-11.5 kft north of I-80 
early Monday and 8.5-11 kft region wide by mid-week.


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.