628
AGUS76 KRSA 261410
HMDRSA

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.


QPF graphics are available at www.cnrfc.noaa.gov/qpf.php



Kozlowski

$$