Hydrometeorological Discussion
Issued by NWS California-Nevada RFC

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AGUS76 KRSA 181658
HMDRSA

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

...PRECIP SHIFTS MAINLY NORTH OF I-80 THROUGH THE UPCOMING WEEK...

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

The synoptic feature of interest over the upcoming week is an upr
ridge currently centered over central Mexico this morning. This high
pressure will build westward over Baja California and expand
northward early next week. At the same time...a deep upr trof will
set up offshore mainly between 140W and 150W. In-between...a
moisture plume will be directed north-northeast from the lower
latitudes toward the Pacific Northwest and the far northern CA
coast.

The first opportunity for precip will be with a s/wv trof moving
toward the BC and Washington coast later in the weekend. This system
looks farther north and weaker on the 18/00Z models...and as a
result...expected precip on Monday will have less southward
progression with amounts trimmed from the previous forecast. Look
for the majority of the precip to remain north of I-80. Freezing
levels will be quite high with an upr ridge extending over the area
and the s/wv trof crossing the coast well to the north. Early
Monday...freezing levels will be near 8500-feet for the CA/OR border
area and 10500-feet along I-80. Then through Monday as heights
continue to build...freezing levels rise closer to 10000-feet along
the CA/OR border and 11500-feet along I-80.

The for Tuesday through Thursday...with the moisture plume
meandering along the Pacific Northwest and far northern CA
coast...the opportunity for mainly light precip across the upper
Klamath River basin and far northwest CA exists. However...without
any significant forcing except for some weak isentropic lift...not
expecting daily amounts to be anything impressive. Freezing levels
will be greater than 10000-feet for the entire area Tuesday through
early Thursday...eventually dropping across far northern areas as
the upr ridge flattens somewhat with an approaching s/wv trof.


.HYDROLOGICAL CONDITIONS...

Thursday/Friday storm continues to move East and out of the CNRFC
basins with moderate precipitation in the Southern Sierra and
Humbolt basins, 1-2 inches on Friday morning. Temperatures are
warming across California. Unregulated rivers from the North Coast
to Southern Sierra are on their recession limbs.


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

DRK/NB

$$



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