Hydrometeorological Discussion
Issued by NWS California-Nevada RFC

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AGUS76 KRSA 221637

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
935 AM PDT Wed Mar 22 2017



Showers and thunderstorms with a cold front moving through brought
precipitation to most of the region in the past 24 hours.  0.4-2
inches fell in the Smith Basin and 0.5-1.7 over the Eel and Russian
River Basins and 0.3-1 inch around the Bay Area and 0.25-0.75 inches
in the Upper Klamath Basin and a half an inch or less on the NE CA
Plateau and SE CA deserts. 1-3 inches with local amounts up to 3.75
inches in the Shasta Drainage area. 0.13-1.3 in the Central Valley
and 0.4-1.6 inches in the Sierra except locally up to 3.15 inches.
0.2-2 inches around the Monterey Bay Area with locally up to 3
inches in the Santa Cruz Mountains and 0.1-1.3 with local amounts up
to 2.15 inches around Point Conception and south along the coast to
Orange County then tapering off to less than a tenth of an inch in
San Diego County. Precipitation amounts generally a tenth of an inch
or less with local amounts up to a half an inch over Nevada except
0.25- 1.00 inch over far western Nevada.


A cold front ahead of an upper trough is associated with a band of
widespread precip stretching from the nrn Sierra down toward the
cntrl coast.  Post-frontal showers are affecting the Shasta drainage
as well as the north coast, and a few showers are affecting portions
of nrn NV.  Precip has been a bit faster and overall heavier than
previous forecasts indicated.  As the trough moves overhead and an
upper jet moves east of the region, expect an overall downward trend
of precip associated with the front but with plenty of showers
lingering behind the front.  Precip should also spread across much
of NV and srn CA this afternoon as well.  Expect precip to decrease
fairly quickly from W to E tonight and early Thu.  Expect Sierra
freezing levels 5000-7000 ft.

Expect precip to spread onto the north coast by Thu afternoon as
isentropic lift increases ahead of the next system.  Expect precip
to spread south and east through Fri night as a cold front works its
way onshore.  Decent onshore flow and upper forcing should lead to
some moderate to heavy precip rates along the nrn CA coast and in
the nrn Sierra, while low-level sly flow contributes to enhanced
amounts in the Shasta drainage as well.  Expect Sierra freezing
levels 5000-9000 ft.


Upper level trough and weakened cold front moving through on
Saturday bringing a few showers to the region. Freezing levels
around 5000-7000ft over the Sierra. Precipitation diminishes
Saturday evening into Sunday morning with a weak ridge between
systems. Precipitation ahead of the next system will move into far
NW CA late Sunday morning and spread south and east to around Point
Conception and over most of Nevada Sunday afternoon into night.  The
06 GFS is slower moving this system through and deeper (forming a
low over southern CA Monday night) compared to the 00z EC and GEM is
in between the EC and GFS.  Freezing levels around 6000-8000 ft on
Sunday over the Sierra.


Periods of rain and some higher elevation snow melt are expected to
produce fluctuating river conditions at moderate to high flows
across much of California and Nevada through the weekend.  Stages
above flood levels will continue on the Humboldt river in Nevada
through the weekend and into the next week at least.  Snow melt is
also contributing to other mountain fed flows above monitor levels
on the Sprague River in Oregon, at Portola in the Feather basin and
on the Truckee and Walker rivers straddling the California and
Nevada state lines on the east side of the Sierra Nevada.

Moderate to high flows will also continue on the Sacramento and San
Joaquin rivers in the central valley.  Controlled reservoir releases
will continue to maintain stages above monitor levels at a dozen or
so main stem locations.

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



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