Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 110505
Area Forecast Discussion
National Weather Service Sacramento CA
905 PM PST Tue Jan 10 2017
Pacific storm impacting Interior NorCal with rain, very heavy
mountain snow, and strong winds. Additional flood concerns will
occur as this storm tracks through. Drier weather expected Friday
into the weekend.
At 9 PM Very Heavy rain was still moving through the Northern
San Joaquin Valley spreading north to around I-80 and east into
the foothills. The area started to enhance over the delta and
spread east flooding many roadways as it did and pushing some
creeks above their banks. At this time Arcade Creek, Dry Creek by
Elkhorn Blvd, Morrison Creek in Florin where forced above their
banks as the heavy rain moved through. A number of other creeks
are above monitor stage so a couple more could possibly move out
of their banks in the next hour or so. Lots of flooded roadways
and downed trees reported as this area moved through. Foothill
areas are still getting very intense rain as well so expect
Heavy snow will continue over zone 69 overnight and into the
morning hours before lightening up so dont expect any improvement
for those roadways until sometime on Wednesday. The strongest
winds are behind us now so expect winds to continue decreasing
Another atmospheric river is impacting Interior NorCal with areas
of moderate to heavy precipitation and gusty wind. Heavy snow has
been occurring in the Sierra Nevada today and will continue
tonight into Wednesday morning. Snow levels have rose above pass
levels in the Coastal Range and Western Shasta mountains, and
thus have dropped the Winter Weather Advisory for those areas.
Mainly rain expected tonight for those areas. Snow levels due lower
back to around 4000 feet towards Wednesday morning, but lighter
showers expected by then.
HRRR/NAM-4K showing heavy precipitation from the Southern Sac
Valley into the Northern San Joaquin Valley, extending east into
the Motherlode and West slopes of the Sierra Nevada this evening.
Moderate to heavy snow will occur in the mountains of Western
Plumas overnight with heavy snow for the West slopes of the
Northern Sierra Nevada. Snow levels continue around 4000 to 5500
feet overnight in Western Plumas and Sierra Nevada with several
additional feet of snow accumulating at pass levels. Some CAPE
indicated over the Central Valley early this evening supporting
potential for isolated thunderstorms.
Surface cyclogenesis occurring off the far NW CA coast resulting
in tight N-S pressure gradient over Interior NorCal. KMFR-KSAC
surface pressure gradient currently at 12 mb with VAD profiles
showing upwards of 50 kts above the surface. Strongest winds
occurring in the northern portions of the Sacramento Valley with
KRDD reporting 37G48 Kts at 23z. Wind speeds likely to increase
further along southern portions of the warning area this evening.
Southerly winds of 25 to 40 mph will be common throughout much of
the warned area with gusts 45 to 60 mph. With saturated soils,
potential for downed trees is high and possible power outages.
Winds expected to decrease some after midnight but remain breezy
Precip turns showery in the Central Valley tomorrow while moist
upslope flow continues steady precipitation across the west slopes
of the Sierra Nevada. Additional snowfall will continue, but not
as heavy as today/tonight. Snow levels will trend down to 3500 to
4500 feet Wednesday and 2000 to 3000 feet Thursday morning.
Additional showers possible Thursday...mainly towards the
foothills and over the mountains...as main upper low digs south
through NorCal. Drier northerly flow and upper ridging build over
NorCal Friday into the weekend.
.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)
Drier weather is expected through the extended period as high
pressure builds into California from the eastern Pacific. This
will finally give area rivers and streams a chance to recede.
Breezy northerly winds may be possible late this week, and it
wouldn`t be surprising to see fog developing in the Valleys. This
drier regime will also allow for colder overnight temperatures.
The next storm on the horizon appears to impact the northern
portion of the forecast area Tuesday into Wednesday with snow
levels 7000 to 9000 feet. JClapp/Dang
Storm is expected to continue widespread MVFR/IFR conditions with
periods of heavy rain tonight. Snow levels 4000-6000 ft into Wed
and lowering to 2500-3500 ft by late Wed. South sfc winds 20-30kts
with local gusts up to 50 kts expected through this evening with
2 to 3 K flight level winds 40-50 kts sustained. Winds gradually
decrease overnight. JClapp/Dang
Winter Storm Warning until 10 AM PST Thursday for West Slope
Northern Sierra Nevada-Western Plumas County/Lassen Park.
Blizzard Warning until noon PST Wednesday for West Slope
Northern Sierra Nevada.
High Wind Warning until midnight PST tonight for Carquinez
Strait and Delta-Central Sacramento Valley-Clear Lake/Southern
Lake County-Motherlode-Northeast Foothills/Sacramento Valley-
Northern Sacramento Valley-Northern San Joaquin Valley-Southern