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Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
640 AM PDT Thu May 21 2026

...ABOVE NORMAL TEMPERATURES THROUGH THE WEEKEND AWAY FROM THE COAST 
AS HIGH PRESSURE SITS OVER THE E PACIFIC...
...AFTERNOON SHOWERS OVER THE CREST OF THE SIERRA THROUGH SUN, 
POSSIBLE LIGHT SHOWERS OVER THE N COAST & CA/OR BORDER MON PM 
THROUGH TUES...

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

High pressure over the eastern Pacific continues to inch closer to 
the west coast. Temperatures the rest of the week are expected to be 
well above normal away from the coast with anomalies of +5 to +15 
deg F and locally higher through the weekend. Chances of afternoon 
showers, and maybe a thunderstorm or two, over the crest of the 
Sierra through the weekend.

Models continue to show a a deeper trough/upper low moving into the 
PacNW early next week but disagree on the details. The 00z ECMWF now 
has a deeper upper low bringing light precip into nw CA Monday night 
spreading across the northern regional border throughout the day 
Tuesday as the system descends into nrn CA/NV. The GFS has a 
shallower trough that lifts northeastward through ID and is much 
drier, dropping only a few hundredths of an inch over the north 
coast Monday night. There is considerable spread amongst the 
ensembles. The AI-ECMWF at Arcata shows anywhere from 0 to 1.1" for 
Monday night while the GEFS has less than half its membership 
showing any precip at all and even then it is less than 0.10". 
Bottom line, uncertainty in the forecast beyond Monday.

High freezing levels the rest of the week at 11.5-13.5 kft with the 
whole area likely above 12 kft by the end of the weekend. Levels 
should drop into Tuesday with that next system, but by how much will 
depend on the depth of that trough or low.


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.