Hydrometeorological Discussion
Issued by NWS California-Nevada RFC

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AGUS76 KRSA 201802
HMDRSA

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
930 AM PST Fri Jan 20 2017

...SERIES OF STORMS WILL BRING PRECIPITATION INTO EARLY NEXT WEEK...

.STAFFING NOTE...

The CNRFC will remain staffed through 10 PM today with forecasts at
3 pm, and 9pm for basins affected by heavier precipitation where
forecasts are expected to exceed critical thresholds.

.24 HOUR PRECIPITATION TOTALS (ENDING JAN 20 AT 400 AM PST)...

Widespread precip fell across the area.  The majority of coastal
areas reported 0.5-1.5" except less than 0.5" portions of the
transverse ranges of srn CA.  Around 0.1-0.6" was reported in the
cntrl valley with 0.5-2" near Lake Shasta.  0.1-0.6" was reported in
the upper Klamath basin with 0.1" or less in NE CA.  West slope
Sierra locations reported 0.5-1.5" with less than 1" on the east
side.  Generally 0.3" or less fell in NV.


.METEOROLOGICAL CONDITIONS (SHORT TERM: FRI AM - SAT PM)...

An upper level low off the Pacific Northwest coast with the
associated cold front moving through Northern and Central CA this
morning bringing widespread precipitation. The front is progressing
into Central and Southern CA the remainder of the morning and into
the afternoon.  Upper level jet nosing into Central and Southern CA
and moisture plume off Point Conception and south. Increased amounts
a bit for the coast from the San Lucia to Orange County and over the
Southern Sierra. NW CA is already behind the front this morning with
scattered showers.
Scattered showers and isolated thunderstorms following the front as
it progresses through the state.  The bulk of precipitation will be
in Southern CA especially over the transverse mountains and San Diego
County in the afternoon with scattered showers and isolated
thunderstorms elsewhere. Freezing levels around 3000-4500 ft for
Northern and Central CA and around 5500 ft for Southern CA. Isolated
to scattered showers Friday night into Saturday afternoon in between
systems. Precipitation will become more widespread Saturday night
with the next system moving into the area. Increased amounts a
little for the Nrn CA Coast from the Smith Basin to the Bay Area and
over the Shasta area for Saturday evening as the system approaches
and southerly winds start picking up.

.METEOROLOGICAL CONDITIONS (LONG TERM: SAT PM - THU AM)...

Models have come into better agreement with a slightly slower/
further north track of the moisture plume with the Sunday system.
This is in line with what the GFS and other models have been showing
for at least a couple days.  As a result, QPF was increased a bit in
areas of nrn CA while also shifting timing approximately 3 hours
slower with the progression of the plume across the srn half of CA.
With models in good agreement now, hopefully subsequent forecast
changes will be minimal as the system nears the region.  Overall,
still expect moisture to be more limited in nrn areas with much more
impressive moisture in the south.  Strong low- and mid-level flow
should aid orographic effects.  Expect heaviest amounts in nrn CA
Sat night into Sun morning with heaviest amounts in srn CA Sun
morning through evening.  Expect lighter showers Sun night with
continued light showers Mon into Tue as a low drops south near the
coast.  Ridging then develops and is expected to kick off a series
of at least several days of dry conditions by Wed.  Expect freezing
levels in the Sierra to range around 4000-7000 ft with the main
precip and lower to 3000-4000 ft by late Sun night.


.HYDROLOGICAL CONDITIONS...

Many rivers and streams in the CNRFC forecast area are currently
above...or are forecast rise above monitor level over the next
several days due to forecast precipitation and reservoir releases. A
few locations are expected to rise above flood stage in the next few
days.

Overflow is forecast to continue for the next several days at
Moulton, Colusa, Tisdale, Fremont, and Sacramento weirs.

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

KL/HSO/KL/SS

$$



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