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AGUS76 KRSA 031411
HMDRSA

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
715 AM PDT Thu Apr 3 2025

...SCATTERED SHOWERS CONTINUE TODAY...
...DRY TO START THE WEEKEND WITH A WEAK SYSTEM MOVING IN SUN...

.METEOROLOGICAL CONDITIONS (SHORT TERM: THU AM - SUN AM)...

Another day with the broad upr trof across the western US with the
upr ridge over the eastern Pacific ever so slowly making its way to
the west coast. Dry northerly flow continues to be the rule across
CA and NV with PW values generally between 0.25- and 0.50-inch. With
just enough moisture and afternoon instability...should once again
see scattered showers develop mainly over the length of the
Sierra...coastal southern CA...and portions of NV. Amounts are
expected to be from a few hundredths of an inch to about 0.10-inch.
Freezing levels are starting out this morning generally from 3000-
to 6000-feet from northwest to southeast. These will begin to
moderate a bit through the day.

For Friday into the beginning of the weekend...look for the broad
upr trof to sharpen a bit and begin to move downstream of the
area...being replaced by a positively tilted upr ridge. This will
bring primarily dry conditions. Freezing levels will rebound by the
end of the period (Saturday 05/12Z) as high pressure moves
overhead...and generally range from 9000- to 11500-feet.


.METEOROLOGICAL CONDITIONS (LONG TERM: SUN AM - WED AM)...

A deepening trough and associated cold front approaches the Pac NW/
Nrn CA coast on Sunday and the short wave trough moves inland Sunday
night and through Nrn NV on Monday. PW plume about 1.3 inches aims
at the Nrn CA coast Sunday/Sunday night with PW around 1.1 inches
along the Nrn CA coast.  The models and ensemble still vary with the
timing (00Z GFS still quicker than the 00Z) and details for lower
confidence in precip amounts and coverage areas for Sunday into
Monday. On the 24hr QPF 50th Percentile Clusters ending 00z Monday,
a little over a third (38%- Canadian 25% and GFS 13% and EC 58%)
ensemble members dominated by the EC have dry conditions for the the
region through 00Z Monday due to slower timing.  The other ensemble
members show precip along the NW CA coast and into the Srn OR
Cascades with amounts 0.5-1 inch along NW CA and less than half an
inch for the Srn OR Cascades.  Ensemble members agree better with
precipitation Sunday night into Monday but differ on the amounts and
coverage areas. On the 24hr QPF 50th Percentile Clusters ending 00z
Tuesday, a little over half the ensembles (53%- Canadian 70%, GFS
90% EC 24%) dominated by the GFS show precip amounts over Srn OR and
along the Nrn CA coast and the Shasta Basin and into the Nrn Sierra
with amounts generally half an inch or less except to around 0.75
inches for the Smith Basin.   28% of the ensembles (Canadian 20%,
GFS 10%, EC 42%) show heavier and more widespread precip over Nrn CA
with amounts up to 2 inches for the Smith Basin and King range and
an inch for the Shasta Basin and precip down to around the I-80
corridor.  The other 19% of the ensemble members (Canadian 10%, GFS
0%, and EC 34%) have 0.5-1.5 inches for NW CA coast and up to half
an inch for the Shasta Basin and into the Feather Basin. The
forecast uses a blend of the latest NBM and WPC mixed with the
previous forecast with mainly light precip along the NW Coast Sunday
morning then increasing and spreading south and east over Srn OR and
Nrn CA in the afternoon/night with light precip possible down to
around the I-80 corridor Sunday night.  Precip amounts for Sunday
into Sunday night 1-2 inches over the Smith Basin and the King Range
and 0.25-0.75 inches for the Srn OR Cascades and Eel Basin and
around a half an inch or less for Shasta Basin and around a third of
an inch or less for the Nrn Sierra and Russian Basins and generally
around a tenth of an inch or less for the Sac Valley and over Nrn
NV. Lingering showers possible over Srn OR and Nrn CA and Nrn NV
into the day on Monday.  Precip amounts to around a quarter of an
inch for the Smith Basin and Srn OR Cascades and generally around a
tenth of an inch or less elsewhere over the north (mainly along the
coast and higher terrain) on Monday.

Another shortwave moves into the Pac NW/B.C. on Tuesday with nearly
zonal flow/weak ridging over the region.  Showers are possible over
the Smith Basin and Srn OR Cascades on Tuesday with amounts
generally around a tenth of an inch or less.

Max temperatures generally near normal to around 10 degrees above
normal over the region Sunday afternoon (except near normal to 10
degrees below normal along Nrn CA coast). Max temps lower to near
normal to up to 15 degrees below normal over Nrn CA and Srn OR on
Monday and generally near normal to around 10 degrees above normal
elsewhere. On Tuesday, high temperatures generally near normal to 15
degrees above normal, except up 12 degrees below normal along the NW
CA coast.  Overnight minimum temperatures generally near normal to
around 10 degrees above normal for most of CA and 5 to 15 degrees
above normal over SE CA and over NV.

Freezing levels generally around 9000-11,500 ft over the region on
Sunday morning then falling to around 4500-7000 ft over Srn OR and
Nrn CA and 8000-11,000 ft over Central CA and 11,000-12,000 ft over
Srn CA and around 7000-12,000 ft over NV (NW-SE) Monday morning.
Freezing levels rising to around 6000-10,000 ft over Nrn CA and
around 7500-12,000 ft over NV (N-S) by Tuesday morning and rise to
around 10,000-13,000 over the region Tuesday night.


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



Kozlowski/Osborne

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