Hydrometeorological Discussion
Issued by NWS California-Nevada RFC

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AGUS76 KRSA 211852
HMDRSA

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
1030 AM PST Sat Jan 21 2017

...LIGHT PRECIP TODAY THEN MODERATE TO HEAVY AMOUNTS EXPECTED
TONIGHT THROUGH SUN...
...LIGHT PRECIP AGAIN MON-TUE...

.24 HOUR PRECIPITATION TOTALS (ENDING JAN 21 AT 400 AM PST)...

Widespread precipitation fell across the region again during the
period.  Coastal areas received generally 1-2", locally lighter in
the Russian/Napa basins.  Central valley locations reported
generally 0.5-0.8", with around 1.2-2.2" near Shasta Lake.  The
upper Klamath and NE CA reported around 0.1-0.5".  West slope Sierra
locations reported around 1-2", with generally less than 1" on the
east side of the range.  Finally, NV totals were generally 0.25" or
less, locally 0.5-1" in higher terrain of nrn NV.


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

Isentropic lift along with an upper jet and associated vort max
aloft are supporting shower activity along the north coast and
across the Lake Shasta area into the Sierra.  A few showers are also
occurring in the cntrl valley, toward the Monterey Bay area, srn CA,
and nrn NV.  Showers are mainly light and are expected to wind down
later today as lift decreases.  Expect freezing levels near the
Sierra around 3000-4000 ft this morning and 4000-5000 ft this
afternoon.

The next system expected to affect the region can be seen developing
near 40N/135W.  Expect precip to begin to increase by late this
evening over mainly nrn CA and continue to ramp up overnight across
nrn/cntrl CA.  A sfc low developing now with a cntrl pressure near
987 MB is forecast to deepen to near 960 MB as it moves to around
130W off the Oregon coast by late tonight.  Thus expect strong SE to
S winds to develop tonight ahead of the cold front.  A moisture
plume is expected to reach the cntrl coast of CA tonight and work
its way across srn CA through the day Sun.  GEFS H85 moisture flux
anomalies are elevated across a wide swath as the plume moves across
the area and reach as high as +6 near the coast.  Expect heaviest
amounts in nrn CA late tonight into early Sun morning with heaviest
amounts in srn CA Sun morning through evening.  Expect freezing
levels in the Sierra to reach 4000-7000 ft Sun morning before
falling to 3000-4000 ft by late Sun night.  Overall, timing was
shifted a little faster in srn CA compared to the previous forecast.
With the strong flow, could see some east-side Sierra enhancement as
well.  Expect generally diminishing showers through Mon morning
behind the front, except light to moderate showers could continue
across portions of srn CA coastal sections through the period as the
upper jet slowly drags south and east across that region.  Expect an
upper low dropping south could provide for light showers across the
region into Tue.  Sierra freezing levels should remain around 3000-
4000 ft.  Expect mainly light precip outside of CA for the few days.
Expect dry conditions from Wed and beyond except perhaps for some
light amounts in the far north late Wed into Thu from a weak system.


.HYDROLOGICAL CONDITIONS...

High water continues on many rivers and streams in the CNRFC
forecast area as a result of precipitation over the past several
days and/or reservoir releases.  Many rivers and streams are
currently above... or are forecast to rise above monitor levels in
the next few days.  A few locations are currently above...or are
expected to exceed flood stage in the next few days due to
additonal forecast precipitation on Sunday into Monday.

Overflow is expected to continue at the Moulton, Colusa, Tisdale,
Fremont, and Sacramento weirs for at least the next 5 days.

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

KL/SS

$$



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