Area Forecast Discussion
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FXUS66 KSTO 131747

Area Forecast Discussion
National Weather Service Sacramento CA
945 AM PST Tue Nov 13 2018

Dry weather with cool nights and above average high temperatures
continues through the week. Diminishing winds ease critical fire
weather conditions, but widespread smoke from the Camp Fire will
continue to impact the area.


Morning Update: Pacific short wave trof encountering the highly
amplified ridge axis over Wrn NOAM won`t bring any rain, but it is
spreading a plethora of high cloudiness over our CWA, masking the
smoke layer from the Camp WF in Butte Co. HRRR smoke loop suggests
the smoke layer will shifting Ewd across the coastal range later
today and overnite. Otherwise, light/lighter winds and limited
mixing height will tend to keep persistent smoke over a large
portion of the region for the next couple of days.

Looks as if this initial batch of high cloudiness will exit our
region Wed afternoon while additional high cloudiness will s spill
over the persistent ridge Wed afternoon and Thu.

There are now rumors of rain over Norcal next week but model
differences continue to cause low confidence in timing. 13/00z ECMWF
suggests as early as Tue nite into Wed and Thu, while the GFS
suggests some rain spreading into our area Wed and continuing into
Thu. The common theme is Wed/Thu. The GFS 5-wave chart forecasts a
displacement of the mean 5H ridge into the mid section of NOAM with
a mean trof over the Ern Pac near 130W which would supporting a
pattern change.   JHM

.Previous Discussion...
Plentiful amounts of high clouds are moving across NorCal early this
morning in advance of a weakening short-wave off the coast.
Current temperatures are a little milder compared to 24 hours ago
across most of the region and range from the upper teens to lower
20s in the colder mountain valleys while the Central Valley is
seeing readings in the mid 30s to mid 40s (some patchy early
morning frost possible again in the outlying areas). Foothill and
mountain thermal belts are currently in the mid 40s to lower 50s.

Easterly surface pressure gradient has relaxed somewhat (RNO-SAC
is down to around 6.5 mbs), but enough remains combined with the
downslope/drainage component for local easterly breezes of 15-25
mph early this morning over ridges and near west-facing canyons
of the foothills and west slopes of the northern Sierra.

Persistent upper ridging over Norcal will result in light/lighter
winds over Norcal and limited mixing heights (1-2 kft), due to
the time of the year, will tend to keep persistent smoke over a
large portion of the region for the next couple of days (smoke
returned to the northern Sacramento Valley last evening).

With no major changes in the weather pattern through the end of
the week, little change from day to day is expected in the
forecast. Smoke may help to keep temperatures locally cooler the
next couple of days, otherwise they will continue to run above


High pressure expected to remain over California as we head into
the weekend. Temperatures are forecast to remain fairly steady
through most of the extended period with the Valley and foothills
seeing 60s to low 70s and the mountains in the 40s to 60s. Models
continue to hint at a pattern change sometime next week. However,
consistency between runs and models is still low. An upper level
trough is expected to finally break down the persistent high
pressure early next week. There is the possibility that this
weather system may bring precipitation to NorCal mid to late next
week, but there is low confidence in timing, location, and
precipitation amounts between the models at this time. HEC



Widespread MVFR likely the next 24 hours across the entire
Sacramento Valley with local IFR conditions due to smoke from the
Butte County wildfire. Northerly winds under 10 knots.



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