Hydrometeorological Discussion
Issued by NWS California-Nevada RFC

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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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