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CNRFC Hydrometeorological Discussion

AGUS76 KRSA 211639
HMDRSA

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
930 AM PST Wed Feb 21 2018

...COOL WITH SCATTERED PRECIP THROUGH THE PERIOD...

.METEOROLOGICAL CONDITIONS (SHORT TERM: WED AM - SAT AM)...

Pattern continues to be conducive to cool system dropping toward the 
region from the north as the upr ridge sits over the east-central 
Pacific...aligned primarily along 150W. Broad upr trof is situated 
downstream over the intermountain west.

The system moving southward across the region today is fairly weak 
and contains minimal moisture. Best shower activity is primarily 
offshore this morning...according to radar imagery. Not expecting 
much in the way of precip affecting inland locations today.

The next system expected to impact the region is currently dropping 
southward across western British Columbia this morning...and will 
begin to bring precip to areas near the CA/OR border this evening 
and overnight before spreading southward across a majority of the 
area on Thursday. This s/wv trof is stronger than the one today and 
the trajectory brings better dynamics inland across the area. It is 
currently looking like best amounts will fall over the Sierra 
between the Feather River basin down toward the Merced River basin 
with totals between 0.25- and 0.50-inch. Elsewhere...look for totals 
remaining somewhere near or less than 0.25-inch. Freezing levels 
will once again plummet as the cold air ushers across the area 
behind the frontal boundary. Look for freezing levels near sea level 
across northern areas... 1000- to 2000-feet for central CA and 
points inland...with close to 3000-feet across southern CA. A weak 
s/wv ridge will move in for later Friday bringing dry conditions. 
But the next s/wv trof will move into the picture early Saturday for 
a return of light precip to the upper Klamath at the end of Day 3.


.METEOROLOGICAL CONDITIONS (LONG TERM: SAT AM - TUE AM)...

Light precip is expected to spread across far northern CA and 
northern NV Sat into Sat night as the wave dives SE.  Expect 
freezing levels roughly 2000-3000 ft.  GFS/ECMWF guidance were about 
6 hours apart in timing with a deeper trough expected to bring 
precip to the region Sun-Mon.  Followed the ECMWF timing for now, 
but a glance at the GEM shows a timing more closely aligned with the 
GFS as well.  If the GFS/GEM are more accurate, timing could be 
slowed a bit with future updates.  Much of the area should 
experience light precip except for CA's central valley, central CA 
coast, and SE CA where dry conditions are expected.  Expect freezing 
levels around 2000-5000 ft.


.HYDROLOGICAL CONDITIONS...

Cold temperatures combined with little to no precipitation are 
resulting in low runoff conditions. All forecast locations within 
the CNRFC area are forecast to remain below monitor levels for the 
next five days. 

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

DRK/KL/BMM

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