Version:  Current  |  Back 1  |  Back 2  |  Back 3  |  Back 4  |  Back 5  |
Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
715 AM PDT Sat Apr 26 2025

...COOL AND WET THROUGH THE WEEKEND...

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

As anticipated...the elongated upr trof off the west coast formed an 
upr low west of Cape Mendocino...which has now dropped southeast and 
is currently located just off Point Conception. Radar imagery 
indicates a few areas of showers this morning with the first in the 
vicinity of the upr low...impacting areas along the central CA coast 
and now moving toward portions of southern CA between Santa Barbara 
and Ventura counties. Another area of focused precip is shifting 
from east-southeast to west-northwest across the central Sierra back 
toward the the southern Sacramento and northern San Joaquin Valleys 
in an area of diffluence aloft in the northeast quadrant of the upr 
low. A final band of precip is from a line of deformation setting up 
from the upper Klamath River basin back to the northern CA coast. So 
far this morning (26/12Z)...automated gauge reports are showing 
amounts remaining in check with totals anywhere from a few 
hundredths of an inch up to about 0.25-inch (greatest right near 
Point Conception).

For today...the upr low has pretty much reached its farthest south 
location and will start to shift off toward the northeast and 
increase its forward speed. This will take the circulation across 
the San Joaquin Valley and southern Sierra before reaching central 
NV by Sunday morning. This trajectory should focus the best precip 
over the area around Point Conception to Los Angeles with 0.25- to 
0.75-inch. The next area of best precip looks to be from northeast 
CA and then down the Sierra along with points east across immediate 
western NV. This area should also see totals ranging from 0.25- to 
0.75-inch with locations along the east slopes of the Sierra seeing 
decent orographics given the easterly flow...especially through the 
morning and afternoon hours. Also...any convective development this 
afternoon could bring some localized heavier totals to these areas 
as SPC indicates a swath of general t-storms from the area near 
Point Conception northeast across the Sierra and the western 3/4 of 
NV. Freezing levels in the vicinity of the upr low will be at their 
lowest as the cold airmass near the core of the system moves 
overhead today. Look for these to drop to 5000- to 7000-feet in 
general. 

Sunday will see the upr low move from NV to northern UT as the 
overall progress of the system once again slows down a bit. This 
will bring a general decrease in precip across much of CA with the 
best amounts over the central Sierra...between 0.10- and 0.25-inch. 
However...closer to the core of the system...amounts over northern 
NV will pick up...especially the Humboldt River basin. Amounts here 
will generally range from 0.25- to 0.75-inch with some localized 
amounts over the Ruby Mountains topping out close to 1.00-inch. For 
Sunday...freezing levels do look to be around 7000-feet for the 
majority of the day as the upr low moves overhead.

By Monday...the upr low will have moved off toward the 
northeast...but will leave behind an elongated upr trof that extends 
from the northern Plains states all the way back across the central 
Rockies before reaching southern CA and northern Baja. This will put 
the region in an area of dry northerly flow aloft. Then by later 
Tuesday into Wednesday a s/wv trof will drop across the region that 
will bring the opportunity for some light precip mainly across the 
interior from the upper Klamath River basin and down the Sierra 
along with points east across NV. This system will linger into 
Thursday as an upr low across southern CA...continuing the chance 
for some shower activity across the Sierra from about Lake Tahoe 
southward.