Scientific Forecaster Discussion
fxus66 ksto 151100
Area forecast discussion
National Weather Service Sacramento California
300 am PST Fri Nov 15 2019
high confidence in dry and mild forecast through early next week.
Very warm over the weekend with record highs possible in North
Sacramento valley. Pattern change still on track around mid week
with some breezy winds and cooler temperatures forecast.
early this morning, clouds have begun to overspread the area as a
trough moved onshore. Radar has picked up on isolated, light
reflectivities over the northern Shasta and coastal mountains with
this passing system, with only light showers expected through the
morning. In the southern SAC valley, some low stratus and mist have
been noted and is expected to dissipate around mid-morning.
The trough splits late Friday with a cut off low forming just off
the coast of socal Friday night, and the northern portion digging
into the central Great Basin Saturday. Ridging builds back into
northern California at this time, remaining through the weekend.
Winds pick up across the northern SAC valley and foothills Saturday
with some gusts up to around 25 mph possible mainly in the
Temperatures will be roughly 5 degrees above average this afternoon,
increasing significantly by Sunday and Monday with afternoon highs
around 10 to 20 degrees above normal. Valley lows each night will be
in the 40s, with mountain lows in the 30s.
Extended discussion (tuesday through friday)...
by Tuesday, a notable shift in the pattern takes place as a
closed low nears the Pacific northwest coast early in the morning.
While a core of the height falls advances toward the upper
intermountain west, some of this energy dips south toward the
California/Oregon border. How this evolves will ultimately dictate
the impacts across the region which likely includes a period of
gusty north to northeasterly winds and a few mountain showers.
Recent ensemble means support a southward track of the upper low
while reaching Southern California by Thursday before exiting
toward The Four Corners region.
While ensemble spread exists with this system, there is a fairly
high signal in the guidance for the mentioned dry, gusty winds
from Wednesday into early Thursday. European model (ecmwf) ensemble probabilities
show fairly high percentages of gusts exceeding 35 mph along the
western side of the Sacramento Valley as well as the foothills and
higher terrain. With decreasing humidities in this flow regime,
fire weather concerns will need to be closely monitored given
historically dry fuels for mid-November. Given strong forcing
underneath the low center, some scattered mountain showers will be
possible. Overall, keep in mind any shift in the upper low track
will alter impacts over the area. Stay tuned for updates on this
forecast in the days ahead.
Regarding temperatures, a cool down will occur in this pattern
but still remains roughly 4 to 8 degrees above average. This
equates to valley highs regularly sitting in the mid to upper 60s
while 40s and 50s will be more commonplace in the mountains. ~Bro
VFR conditions are expected the next 24 hours except for local
MVFR from ksmf southward due to lowering ceilings and
visibilities, generally through 17z. A few scattered showers are
possible over the northern Sacramento Valley through 17z. While
most sites will see winds below 10 knots, some locally higher
gusts can be expected at ksck and kmod between 21-00z. ~Bro