Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 011147
Area Forecast Discussion
National Weather Service Sacramento CA
347 AM PST TUE DEC 1 2015
A FEW SHOWERS ARE POSSIBLE THROUGH WEDNESDAY ACROSS FAR NORTHERN
CALIFORNIA. THE NEXT STORM SYSTEM ARRIVES BY THURSDAY AFTERNOON
BRINGING MORE WIDESPREAD PRECIPITATION TO THE REGION ALONG WITH
GUSTY SOUTHERLY WINDS. SNOW WILL BE LIKELY OVER THE MOUNTAINS
THURSDAY EVENING WITH POSSIBLE TRAVEL DELAYS.
Some clouds along with higher dew points in the wake of
yesterday`s weak system have resulted in milder temperatures
across the region early this morning. While readings are still
cold, they`re running about 5 degrees warmer in the valley
compared to 24 hours ago and 5-15 degrees milder in the mountains.
Dew points still range from the mid 20s to lower 30s in the
valley, so some frost still likely again this morning.
Ridging over NorCal will delay the eastward progression of the
next offshore frontal system, providing dry conditions and a
little milder temperatures today. Front stalls off the coast of
northwest California tonight and Wednesday, but enough lift from
warm-advection may result in some light precipitation across far
Stronger system moves into the region on Thursday bringing a
combination of moderate amounts of precipitation along with gusty
southerly winds. Models in pretty good agreement swinging a strong
short-wave into NorCal Thursday afternoon. While this feature
should act to enhance precipitation over the region as it taps TPW
plume of around an inch, it will also delay its arrival as the
larger-scale trough takes on more of a negative-tilt.
It`s still looking to be quite breezy to windy across the region
on Thursday as southerly pressure gradients tighten ahead of the
approaching front. However, the main surface low will be well
north of the region so we`ll likely see a rather quick shot of
wind ahead of the front. Peak winds in the valley may reach 40-45
mph with higher gusts in the mountains.
System quickly progresses east Thursday night with showers
lingering across the region into Friday. Main travel impacts due
to snow likely to begin the northern Sierra Thursday afternoon and
continue until at least Friday morning.
.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)
Extended period starts out dry on Saturday under back edge of
upper ridging over the western U.S. A frontal band offshore will
send some cloudiness over the northern forecast area with daytime
highs expected to come in around normal. The second half of the
weekend looks wet for most of the CWA as a Pacific frontal system
makes its way through the north state. Models agree that this will
be a fairly rapid moving system and not a big precipitation
producer. Snow levels will remain moderately high for this time of
year. There may be a brief break in Norcal Precipitation early
Monday before another Pacific storm system pushes into the
northwest corner of the state in the afternoon. GFS/ECMWF timing
similar but GFS somewhat deeper with this system. Either
way...models ridge up over the EPAC quickly behind this system
limiting significant precipitation to the northern half of the
CWA. Overrunning could bring some precipitation to the northern
forecast area Tuesday but models have been trending towards
stronger ridging so adjustments to precip line will likely be
needed with subsequent model runs. Precipitation or not...a more
mild airmass should bring daytime temperatures back to at least a
little above normal Tuesday.
VFR conditions TAF sites next 24 hours. Increasing high/mid clouds
after 00z with weak front moving into northwest CA. Chance of
light rain Northern mountains and northern Sacramento valley after
06z. Sustained winds generally below 15 knots mainly northerly
today turning mainly southerly tonight and Wednesday.