Hydrometeorological Discussion
Issued by NWS California-Nevada RFC

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AGUS76 KRSA 181747
HMDRSA

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
930 AM PST Wed Jan 18 2017

...SERIES OF STORMS WILL BRING PRECIPITATION INTO MONDAY...

.24 HOUR PRECIPITATION TOTALS (ENDING JAN 18 AT 400 AM PST)...

Warm advection precip spread across portions of nrn CA and srn OR
during the period.  Totals were around 0.5-1" in the Smith basin and
generally less than 0.5" for the remainder of the north coast.  A
few hundredths of an inch fell in the Sacramento Valley with up to
around 0.15" in the Shasta drainage.  The upper Klamath received up
to 0.4", while a few hundredths of an inch affected NE CA and a
couple locations in wrn NV.


.METEOROLOGICAL CONDITIONS (SHORT TERM: WED AM - THU PM)...

A 1.1 inch pw plume around the bay area at 15Z will continue to drop
south during the day today. Winds will increase during the day and
peak this afternoon and early evening. 700 mb southwest winds 55-75
kts with southerly winds 45-55kts at 850 mb will bring good
orographics to Shasta and the Coastal Range and the Sierra.

Increased precipitation along the Northern CA coast and around Mt
Shasta and around the I-80 corridor this morning. Also spread precip
farther south into Central CA this morning with a band moving
through. Increased precipitation amounts for this afternoon for
Northern and Central CA especially in the Russian River Basin and
along the Sierra and around Mt. Shasta. Also, decreased freezing
levels around 500 ft or so today. Blue Canyon was snowing and about
freezing at 8 am and colder air was trapped for lower snow levels
around Shasta area (snow levels around 2400 ft). Freezing levels
will drop late this afternoon into tonight behind the cold front to
around 3500 ft in the North and around 5500 ft for the Central
Sierra and around 6500 ft for the Southern Sierra.  Moisture plume
drops off the southern ca coast overnight with precip spreading into
Southern CA. Bulk of precipitation in Southern CA and southern NV
and scattered showers north on Thursday as an upper level trough
moves over the area.


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

The overall forecast with the Fri system has not changed much from
yesterday.  Expect the best moisture to affect in the srn half of
the region as a moisture plume makes a glancing blow to srn CA.
There is a possibility of heavy precip along the transverse ranges
of srn CA and especially in SW CA where the wly flow direction is
ideal for orographic enhancement.  Elsewhere, expect more moderate
precip rates further north in CA with only light amounts outside the
state.

GFS/ECMWF show decent agreement with the Sun system, but there is
still plenty of room for improvement.  The ECMWF is a bit faster/
further south with the plume and the progression of the system.
Overall, our forecast is based on a blend of the two solutions with
manual adjustments in the areas of heavier precip.  Expect heaviest
amounts in the Shasta drainage, Sierra, and coastal terrain.  This
system is reasonably quick to move across the area, similar to the
Fri system.  Overall, expect freezing levels to remain around 4000-
6000 ft across the Sierra and a bit higher in srn CA.  Expect drying
into Mon.


.HYDROLOGICAL CONDITIONS...

Precipitation expected over the next 24 hours will cause sharp rises
on many coastal rivers.  Monitor levels are expected to be exceeded
at a number of locations in the Mad, Eel, lower Klamath, Navarro,
and Russian.  The Navarro is the only location expected to rise
above its flood stage.

The Upper Sacramento is expected to see monitor levels exceeded at
most locations with a few expected to rise above flood stage.  These
locations are TEHC1, VWBC1, and ORFC1. Moulton, Tisdale, Colusa,
and Fremont are all expected to be flowing.

The Cosumnes is once again expected to rise above monitor stage at
MHBC1, and also down at THTC1.  Monitor stages are expected to be
exceeded along the lower reaches of the Tuolumne and Merced rivers.

Inflows to Sacramento/San Joaquin reservoirs are expected to be
fairly low because of the cold temperatures expected over the next
5 days.


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

KL/HSO/KL/BW

$$



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