Hydrometeorological Discussion
Issued by NWS California-Nevada RFC

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AGUS76 KRSA 261637
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Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
930 AM PDT Sun Mar 26 2017

...TWO SYSTEMS TO MOVE THROUGH THIS WEEK...

.24 HOUR PRECIPITATION TOTALS (ENDING MAR 26 AT 500 AM PDT)...

Precip associated with an exiting upr trof was most widespread
across central CA and southern/eastern NV mainly early in the period
on Saturday. Overall amounts across CA remained near or less than
0.10-inch...but greater totals were observed over portions of NV
where amounts ranged from a few hundredths on the fringes of the
precip shield and up to 0.25- to 0.50-inch over east-central NV.

A few light showers also lingered along the north coast yesterday
from about Arcata northward to the CA/OR border. Amounts ranged from
a couple hundredths of an inch to 0.25-inch over the wettest
portions of the Smith River basin.


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

An upr trof is situated over the northeast Pacific with the primary
circulation spinning near 50N/140W this morning. A cold front
extends from this vertically stacked system arcing generally along
130W...while a warm front resides just off the north coast. Radar
imagery shows weak echoes streaming inland across the upper Klamath
River basin and northern CA this morning with measurable precip
through 26/14Z reaching the Eel River basin inland to the Shasta
Lake drainage and far northern end of the Sacramento Valley. Blended
TPW and Trimble GPS-Met stations show PW values along the coast
peaking at or just above 0.75-inch...so not an overly impressive
moisture plume ahead of the cold front.

Overall...models are in reasonable agreement with the progression of
this system across the region today into tomorrow with the upr trof
axis showing a tendency to split as it moves onshore tonight and
forms a cutoff low with the southern piece across the lower Colorado
River basin late Monday into Tuesday. Best precip amounts will be
focused on the higher terrain of northern CA and northern NV. Look
for freezing levels to start out in the range of 5000- to 7000-feet
across the northern half of the area and then drop to between 4000-
and 6500-feet after cold frontal passage.

An upr ridge centered to the southwest of the region will build
across the area on Tuesday and bring dry conditions to CA and
NV...awaiting the next system to arrive from the northwest on
Wednesday and lasting through Thursday. There has been some model
discrepancies with the trajectory of the system as it moves across
the region...but the 26/00Z models are showing better agreement as
compared to previous model cycles. This thinking would bring wetter
conditions to northern and eastern areas and cooler temperatures to
much of the area. By early Thursday...the upr trof axis will reach
the west coast with the base of the system along the north coast.
Then the system will dive toward the southeast along the Sierra
crest before carving out a deep upr trof and eventually forming a
cutoff low somewhere across southern NV on Friday before beginning
to shift east of the area late in upcoming week. Overall...a general
blend of the 26/00Z EC and GFS was used for this system.


.HYDROLOGICAL CONDITIONS...

Rivers continue to recede this morning from the precip that fell
late Friday and Saturday. The next system is moving onshore this
morning and will bring very small renewed rises to a few streams,
mainly on the coastal rivers where the heaviest precip will be
concentrated.

Flows will begin to drop on the Feather River Monday as Oroville is
expected to reduce outflow. Flows on the San Joaquin will continue
to remain high for the next few days, but will start to see a bit of
relief in the upper reaches of the system as Friant outflows are
reduced. The flood wave peak has reached Battle Mountain on the
Humboldt. Expect flows to remain near or above flood stage on the
lower portion of the river through the week. Flows will continue to
recede on the upper portion of the Humboldt River through the week.


More information on the CNRFC website at http://www.cnrfc.noaa.gov

DRK/MI

$$



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