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CNRFC Hydrometeorological Discussion

AGUS76 KRSA 241625
HMDRSA

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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