Scientific Forecaster Discussion
fxus66 ksto 171122
Area forecast discussion
National Weather Service Sacramento California
322 am PST Fri Jan 17 2020
showers taper off across the region early today. Mainly dry and
milder weather is expected over the weekend before precipitation
chances return next week.
radar indicates light to moderate snow showers continuing early
this morning across the west slopes of the northern Sierra and
southern Cascade Range. Heavier showers may bring additional
snowfall accumulation rates of up to an inch/hour until around
sunrise. Precipitation has ended across the remainder of the area.
The upper trough lifts into the northern rockies this morning as
short-wave ridging moves over norcal. Remaining showers over the
Sierra are then expected to diminish quickly in the morning. Some
light precipitation may linger across the mountains of northern
Shasta County into this evening as warm-advection and moisture
convergence increase ahead of the next system.
Satellite imagery shows a maturing extratropical cyclone off the
coast of the pacnw. This system will give the far northern portion
of the forecast area a chance of precipitation on Saturday as it
moves ashore well north of the region. Otherwise, dry and milder
weather is forecast across the area through the weekend.
Next chance of more widespread precipitation returns next week
(later monday) as another trough approaches the West Coast.
Extended discussion (tuesday through friday)...
unsettled weather is expected through the extended period.
The gefs is trending toward the slower onset of the next
significant system early next week, as the European model (ecmwf) ensemble has
been showing in the past few runs. This suggest the bulk of the
precipitation will be timed for Tuesday. This is a warmer and
somewhat less wet system than the one currently impacting the
area. Snow levels are currently expected to be around blue
canyon's elevation (5280 feet), so impactful snow should be mainly
above 6000 feet. Early estimates of snowfall are around a foot to
a foot and a half. Anyone planning travel over mountain passes
should be prepared for possible delays and chain controls. This is
a fairly quick moving system, with valley rainfall amounts of
around a quarter to three quarters of an inch. By Wednesday, just
lingering showers are forecast, mainly over the mountains.
Thursday into Friday another system could bring mainly light
mountain precipitation, but confidence is low. The best potential
for precipitation is over the northern mountains. Ek
the bulk of the current storm system is exiting to the east.
Lingering snow showers are still possible this morning over the
mountains with areas of LIFR, though. Periods of MVFR, IFR/LIFR
conditions are possible this morning in the valley due to areas of
br and low cigs. Some local patches of fog are possible in the
northern San Joaquin, but cloud cover should limit this to mainly
br in the area, through 18z. Ek
Winter Storm Warning until 6 am PST early this morning for West
Slope northern Sierra Nevada-western Plumas County/Lassen park.