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AGUS76 KRSA 221451
HMDRSA

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
650 AM PST Sat Feb 22 2025

...MODERATE/HEAVY PRECIP LATER TODAY INTO SUN FAR NW CA AND SW OR...
...WEAKER SYSTEM IMPACTS SIMILAR AREAS ON MON WITH DRYING TUE-THU...

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

A positively tilted upr ridge continues to extend across CA and then
to the north-northeast over the interior of western Canada this
morning. Offshore across the Pacific...general southwest to west
flow aloft is advecting a surge of moisture from the lower latitudes
west of Hawaii toward the west coast...now making its way within
130W...and expecting it to reach the Pacific Northwest and CA coast
late this morning or early this afternoon with nearly 1.00-inch PW.
Precip will primarily impact coastal areas of southern BC and the
Pacific Northwest with the southern extent of this moisture surge
affecting portions of northwest CA and southwest OR with the best
precip totals continuing to look across the Smith River basin and to
a lesser extent the lower Klamath River basin up to the crest of the
southern OR Cascades. As the available moisture increases across the
region...condensation pressure deficits will drop...and at the same
time WAA/isentropic lift will ramp up across areas near the CA/OR
border with the best precip expected between 23/00Z and 23/18Z. Then
into the afternoon hours on Sunday...a s/wv trof will make its way
toward the WA coast. The associated moisture plume will narrow and
push inland with the cold front. Precip will slowly taper off across
northwest CA and southwest OR...waiting for the next s/wv trof
expected to arrive on Monday. This system will have less moisture to
work with...but again northwest CA and southwest OR will see precip
ramp up again to a lesser extent as compared to later Saturday into
Sunday. This s/wv trof will reach near Vancouver Island and then
weaken as it moves inland mainly along the US/Canada border area. In
the wake of this system...look for a robust upr ridge to pump up
along the west coast...bringing warmer temperatures and dry
conditions from Tuesday through the middle of the week. Models are
hinting at an upr low undercutting this upr ridge by the end of the
week and reaching the west coast...but as of now...dry conditions
look to be on tap through at least Friday morning.

During the periods of precip near the CA/OR border later today into
Sunday...the freezing levels will be from 7000- to 9000-feet. As the
s/wv trof on Monday moves inland to the north of the area...these
will fall down to about 4500-feet late Monday into early Tuesday.

Overall precip totals through early Tuesday will be greatest over
the Smith River basin from 5.00- to almost 8.00-inches. The next
best area for precip amounts will be the crest of the southern OR
Cascades near Crater Lake with approx 2.00- to 4.00-inches. Precip
totals rapidly drop off south toward Cape Mendocino across the Eel
River basin (0.50- to 2.00-inches) and then inland toward the Shasta
Lake drainage (0.25- to 0.75-inches). A few hundredths of an inch to
0.10-inch is possible down to the Russian River basin and inland to
the Feather River basin.


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



Kozlowski

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