Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Sacramento California
342 am PDT Wed Oct 26 2016
wet and unsettled weather continues this week with a brief break
today, then continues into early next week as several weather
systems move across the area.
rain has retreated to north of Redding overnight where some warm-
advection and upslope flow is continuing to wring out light
amounts. Partly to mostly cloudy skies cover the remainder of
interior norcal and temperatures remain generally mild - 40s and
lower 50s in the mountains with 50s and lower 60s elsewhere.
Satellite imagery shows the next system maturing as it moves north
off the pacnw coast with the trailing cold front nearly stationary
off the norcal coast. The front is expected to make little if any
eastward progress today, so most of interior norcal will enjoy a
brief return to dry and mild weather lasting through tonight.
The period from midday Thursday into midday Friday is looking
increasingly wet for much of the region as another wave lifts up
from the southwest around the persistent Gulf of Alaska trough. It
looks like this system will interact with deeper moisture moving
up from the south (some of it originating from seymour), and with
the front remaining draped across norcal a prolonged period of
steady light to moderate rain can be expected. Quantitative precipitation forecast in excess of an
inch will be possible in the Central Valley with several inches
likely in the northern Sierra. Snow levels will remain very high
with little to no impact to travel anticipated.
Showers are expected to linger later Friday into Saturday as
moist southwesterly flow continues across the region, especially
in the northern Sierra where upslope flow will continue to enhance
Extended discussion (sunday through wednesday)
active weather pattern will continue for much of the extended
period. Models in general agreement although vary just a bit in
timing of each wave and precip amounts. Next wave progged to move
across the area Sunday into early Monday. GFS remains on faster
side of the guidance envelope with European model (ecmwf) lagging about 6 hours
behind. Regardless, another shot of widespread precipitation
likely during this timeframe. This wave looks fairly wet,
especially across higher terrain, and colder than previous systems
this week. Snow levels will lower during the day Sunday into
Monday morning and will fall below major pass levels. Accumulating
snow a good bet down to around 7000 feet which would serve to
cause some travel impacts, especially given busy weekend traffic.
Breezy winds will accompany the system with locally gusty
conditions across higher terrain.
System should shift to the east during the day Monday which would
keep Halloween forecast dry Monday evening for trick or treaters
in most areas. Next system will move onshore on Tuesday, but this
one looks weaker than sunday's at this point with light
precipitation amounts. Additional systems possible past Tuesday
but model solutions differ. Below normal temperatures will rule
through the period. Ceo
VFR conditions next 24 hours outside of some patchy MVFR fog that
may develop along portions of the valley early this morning. Winds
5 to 15 kts across northern SAC valley and generally less than 10
kts across rest of the valley terminals.