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 Tue Nov 21 2017

...LIGHT PRECIP MAINLY NORTH COAST AND SRN OR THROUGH THU...
...POTENTIAL FOR MORE WIDESPREAD PRECIP AMOUNTS THIS WEEKEND INTO
EARLY NEXT WEEK...

.METEOROLOGICAL CONDITIONS (SHORT TERM: TUE AM - FRI AM)...

Weak warm advection and some light showers continue over far
northern CA and southern OR in the wake of yesterday`s warm frontal
precip that was widespread over northern CA and southern OR with
heavy amounts near the coast.  Expect light precip to continue for
the north coast and southern OR Cascades through late Wed as a
couple of fronts move nearly parallel with the coast.  The bulk of
the associated precip is expected to remain north of the region and
just off the northern CA coast.  By late Wed night into Thu, expect
the ridge over the region to break down enough to allow a weak cold
front to bring a bit higher precip totals to the far north coast
with light amounts across southern OR and far northern CA.  This
should start to taper off Thu night.  Expect freezing levels to
remain above 10,000 ft through the period until Thu when levels drop
a bit to 7000-10000 ft behind the front.


.METEOROLOGICAL CONDITIONS (LONG TERM: FRI AM - MON AM)...

Ridging on Friday will end the week with dry conditions, though the
next system is not far behind. By Friday night a frontal system is
expected to drop into the region ahead of an Eastern Pac trough.
Pulling in a pool of approx 1.25" precipitable water, this system is
expected to bring light precip to the North Coast and Shasta area
through much of the day Saturday, with moderate amounts over the
Smith Basin. Freezing levels are expected to be around 7500-8500 ft
at this time.

By Sunday, the upper low is expected to drop southward into the Pac
NW, sending a second frontal band into Northern CA. Models differ a
bit in strength, with the Ec taking a wetter approach than the
GFS/Canadian consensus. The moisture appears to outrun the front,
leading me to err more towards the drier GFS/Canadian solution.
expect conditions to dry out through the day on Monday.


.HYDROLOGICAL CONDITIONS...

No locations are at or forecast to exceed monitor stage. The
majority of preipitation over the last 24 hours occurred in the
first 12 hours over the North Coastal and Klamath watersheds. Most
rivers in these watersheds peaked in the last 24 hours and are in
recession, while some will peak in the first half of today.

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

KL/JM/BM

$$



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