Hydrometeorological Discussion
Issued by NWS California-Nevada RFC

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AGUS76 KRSA 141719
HMDRSA

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
930 AM PST Thu Dec 14 2017

...DRY EXCEPT FOR A WEAK SYSTEM OVER THE FAR NORTH LATE FRIDAY...

.METEOROLOGICAL CONDITIONS (SHORT TERM: THU AM - SUN AM)...

High pressure continues to dominate the region, with the positively
tilted ridge axis sitting just off the west coast. Humidity
continues to be well below normal, with the morning sounding at Reno
picking up 0.16" pwat, and measuring 0.29". The next hint of
something trying to break through the ridge comes on Friday, as a
s/wv trough aims to weaken the ridge and move through NorCal. While
expected to pull a nearly 1" pwat plume onshore near the OR/CA
border, antecedent dry conditions will make it difficult for much
precip to accumulate. Expect 0.1-0.2" precip Friday night into
Saturday, mainly near the OR/CA border and into Northern NV. High
pressure should rebuild over the rest of the weekend.


.METEOROLOGICAL CONDITIONS (LONG TERM: SUN AM - WED AM)...

An upr ridge over the far eastern Pacific on Sunday and Monday will
bring continued dry conditions to the region. However...the models
are starting to hint at the potential for the upr ridge flattening
at least temporarily...allowing for a s/wv trof to move across the
northern half of the area. Some timing differences still left to
iron out with the 14/00Z GFS just slightly slower than the EC. For
now...followed a general blend of the two. This would bring light
precip to the Smith River basin as early as Tuesday afternoon and
then spreading inland toward the CA/NV border and south to the I-80
corridor.

Beyond the forecast period...the EC digs a cold upr low over the
Great Basin and carves the system back toward the west coast. The
GFS is much farther to the east with bringing the system in from
Canada toward the Rocky Mountain states. As a result...the upr ridge
that re-establishes itself over the eastern Pacific looks to be
somewhere between 130W and 140W.


.HYDROLOGICAL CONDITIONS...

No precipitation within CNRFC region over last 24 hours. Runoff
contributions from baseflow, and snowmelt at higher elevations.
River locations are forecast to remain below monitor levels during
the forecast period (next 5 days).

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

JM/DRK/BMM

$$



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