Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Sacramento California
908 am PDT Sat Oct 25 2014
cold front will bring strong winds and precipitation today.
Thunderstorms expected with heavy rain, accumulating small hail, and maybe
even isolated weak tornadoes. Snow levels will come down to below
Sierra passes tonight. A brief break late Sunday into Monday will
be followed by potentially more wet weather mid next week and
again late week.
At 8 am, the main band of precipitation with the cold front was
oriented SW to NE in a line including Oakland, Vacaville, Chico,
Shingletown, and Newell. Winds continue to be fairly gusty in
parts of norcal, especially over the Sierra crest and in the
Sacramento Valley from Chico northward. The Redding & Red Bluff
airports have already had peak gusts over 40 mph this morning.
Some Sierra ridge-top peak gusts have been over 70 mph. Winds will
continue to be breezy to gusty for much of norcal today. No
changes anticipated to this morning's forecast package as emphasis
remains on the wet and windy weather along with thunderstorms -
some of which may become severe with weak tornadoes possible. Jbb
Previous discussion...southerly winds have dramatically increased this
morning. We have added wind advisories to the coastal range and
lower foothills of Plumas and Shasta counties, to go with the Wind
Advisory already in place over the Sacramento Valley and western
Delta. We have also issued a High Wind Warning for the higher
Sierra into tonight. As the front approaches and passes later this
morning and afternoon, winds will continue to increase to 15 to 30
mph with gusts 40 to 50 mph in the valley and 50 to 90 mph over
higher terrain. This could cause some trees and even some power
poles to come down, potential causing some localized power
outages. Remember that leaves are still on the trees, so these
stronger winds can potentially produce more damage to trees. Winds
should be decreasing this evening.
Shasta County mountains could see up to 2 inches of precipitation
by Sunday morning with good orographics with the southerly winds.
Snow levels will be around 8000 ft this morning and drop down to
around 5300 to 6500 ft on Sunday morning. Snow accumulations up to
10 inches are possible on Mt Lassen and up to 4 inches possible
over the higher Sierra passes. Consequently, motorists should be
prepared for possible winter driving conditions in the mountains
this weekend. Good instability and shear this afternoon behind the
cold front will bring a threat of thunderstorms and possibly weak
tornadoes, especially within the northern and central Sacramento
Valley. Precipitation will taper off on Sunday with showers mainly
lingering over the Shasta County and down the Sierra. High
temperatures this weekend will be in the mid 60s to low 70s in the
valley and mid 30s to low 50s in the mountains. Monday and Tuesday
will be drier and warmer with ridging dominating, expect for a
slight chance of rain over western Shasta County by Tuesday
Extended discussion (wednesday through saturday)
Amplifying ridge forecast over the western US during the middle of
next week as another trough deepens over the eastern Pacific. This
will likely keep all but the far northern portion of the forecast
area precipitation-free into Thursday. Forecast confidence
decreases later in the week as significant differences develop
between the models in the handling of the trough as it moves onto
the West Coast Halloween and next weekend, though it appears much
of the region will see a chance of precipitation sometime next
Friday or Saturday.
Pacific cold front moves across the area today bringing rain and
increasing winds along with areas of MVFR conditions to the valley
and widespread IFR conditions to the mountains. Wind gusts to 45
mph will be possible after 12z, especially over the northern
Sacramento Valley and gusts over 50 mph will be likely over the
northern Sierra Nevada. Scattered showers along with isolated
thunderstorms will be likely behind the front this afternoon into
High Wind Warning until 11 PM PDT this evening Burney Basin /
eastern Shasta County...West Slope northern Sierra Nevada...
western Plumas County/Lassen park.
Wind Advisory until 11 PM PDT this evening Clear Lake/Southern
Lake County...mountains southwestern Shasta County to Northern
Lake County...northeast foothills/Sacramento Valley...Shasta
Lake area / northern Shasta County.
Wind Advisory until 8 PM PDT this evening Carquinez Strait and
Delta...central Sacramento Valley...northern Sacramento Valley...
southern Sacramento Valley.