Hydrometeorological Discussion
Issued by NWS California-Nevada RFC

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Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
830 AM PST Fri Nov 24 2017

...WIDESPREAD PRECIP EXPECTED LATE SAT INTO MONDAY...
...LIGHT PRECIP IN THE NORTH TUE-WED...

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

A few showers over Northern Nevada mainly north of I-80 as a weak
system brushes by the area during the day. Elsewhere, dry conditions
with weak ridging between systems today. Warm air advection will
bring precipitation back to NW CA and Southern Oregon on Saturday,
mainly Cape Mendocino and North.  PW plume drags south off the
Northern CA coast Saturday evening and to around the Bay Area (1.7
in) Sunday morning. This will bring more widespread and increase
precipitation over Northern CA on Saturday night into Sunday and
into Central CA on Sunday.  The upper level trough digs more than
yesterdays model runs and along the coast Sunday night into Monday
morning.  Increased precipitation amounts a little on Sunday into
early Monday, especially along Central CA coast and Northern and
Central Sierra with the system tracking farther south and ample
moisture.

Freezing levels above 10,000 ft on Saturday drop down to around 6000
ft in the far north to around 8000 ft for the Northern Sierra on
Sunday and dropping to around 4500 ft in Shasta region and 5000-
7000ft for the Northern and Central Sierra by Monday morning with
showers behind the cold front.

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

Mon morning, expect an upper low to be either just pushing into the
central CA coast or moving across central CA, depending on the
model.  The ECMWF is slowest with pushing this feature across the
area, GFS fastest, and GEM in between.  Models agree well on
lingering showers across much of the region Mon morning, with most
widespread/heaviest amounts in the Sierra, especially the southern
half of the range.  Expect showers to wind down and shift east Mon
afternoon into the evening with dry conditions by later Mon night.
Freezing levels should be around 5000-8000 ft in the Sierra early
Mon morning and lower to around 5000-6000 ft later in the morning.
Expect levels around 5000 ft further north into southern OR, while
levels start off 7000-10000 ft in northern NV and lower to 6000-8000
ft.

Expect a wave to clip northern portions of the area Tue-Wed,
bringing light showers to NW CA/southern OR Tue and NE NV on Wed.
Expect freezing levels around 5000-7000 ft.

.HYDROLOGICAL CONDITIONS...

A few minor rises on rivers across the north coast this morning as a
result of precip that fell across the area yesterday. Rivers will
slowly recede today before some minor renewed rises later Saturday
into Sunday with the next system. All locations across the area are
expected to remain well below monitor levels, with the exception of
the Truckee River at Truckee where outflows from Tahoe could push
the river to monitor stage on Sunday.


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

HSO/KL/MI

$$



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