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AGUS76 KRSA 231513
HMDRSA

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
715 AM PST Sun Feb 23 2025

...PRECIP SLOWLY TAPERS OFF TODAY ACROSS FAR NW CA AND SW OR...
...ANOTHER DISTURBANCE WILL BRING PRECIP ON MON TO PARTS OF NRN CA...
...DRYING FOR THE MIDDLE OF THE WEEK...

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

As anticipated...precip ramped up across far northwest CA and
southwest OR as the deep moisture plume reached the coast yesterday
afternoon with increasing WAA/isentropic lift into this morning.
Looking at automated precip gauge data...best totals were observed
over the Smith River basin with 1.50- to 3.00-inches...rapidly
dropping off inland to the Shasta Lake drainage and southern
Cascades (0.25- to 0.50-inch local to 1.00-inch near Crater Lake)
and south to the Eel River basin (0.10- to 0.50-inch).

Precip continues this morning over far northwest CA and southwest OR
with the current 6-hour period ending at 23/18Z bringing another
1.00- to just over 2.00-inches to the Smith River basin...dropping
off the 0.50- to just over 1.00-inch for the lower Klamath River
basin and crest of the southern OR Cascades near Crater Lake.
Then...as a s/wv trof currently crossing 140W just above 40N
continues to make its way to the northeast and reaching the WA coast
late this afternoon or early evening...the best precip amounts will
lift northward along the OR coast as the moisture plume narrows a
bit and intersects the coast along the far southern OR coast. As the
s/wv trof moves inland across northern WA tonight...look for precip
to really back off across northwest CA and southwest OR...waiting
for the next system to arrive along the Pacific Northwest coast to
bring a final round of precip with this event on Monday...developing
in the late morning or early afternoon hours. This system has less
moisture available to work with...and the cold front will sweep
across northern CA reasonably quick...limiting precip amounts. Best
totals still will be over the far northwest corner of CA as the
Smith River basin experiences another 0.50- to 1.00-inch with
amounts dropping off once again inland and to the south (0.10- to
0.50-inch for the southern Cascades and Eel River basin) to only a
few hundredths of an inch over the Russian and Feather River basin.

Freezing levels today will pretty much remain in the range of 7500-
to 9000-feet near the CA/OR border where precip is expected. Then
into the system tomorrow... these will drop as the cold front sweeps
across northern CA. By late Monday into early Tuesday...look for
freezing levels down to about 4000-feet near the CA/OR border and
7000-feet from the Russian inland to the Feather River basin.

After this system clears the area early on Tuesday...an upr ridge
will build over the west coast spreading well up into western
Canada...which will bring a dry and warm to the region with weak
flow aloft. Most likely some of the warmest temperatures will be
experienced for the middle of the week as anomalies will jump to
plus 5- to plus 15-degF...with the greatest departures from normal
across coastal southern CA.

For Thursday through the end of this week...a s/wv trof will
approach the eastern Pacific with the majority of the 23/00Z models
showing the system split with the northern piece traveling well to
the north of the area across BC and WA...while the southern piece
forms a cutoff low off the central CA coast. Models for the most
part are keeping any precip associated with this feature offshore
with the 23/00Z CMC the only one showing a few showers along the
central CA coast on Thursday. Then as the system drops southeast
toward the southern CA coast for Friday...there may be enough
moisture and lift to generate some scattered showers across areas
between Point Conception and the CA/MX border.


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



Kozlowski

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