Area Forecast Discussion
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FXUS66 KSTO 121843

Area Forecast Discussion
National Weather Service Sacramento CA
1040 AM PST Mon Nov 12 2018

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


Morning Update: Light/lighter winds over Norcal and limited mixing
heights (1 kft - 1.5kft), due to the time of the year, will once
again keep persistent smoke over a large portion of the CWA.
Satellite indicates some improvement on the east side of the CWA
with the help of downslope flow overnight. But during the day, with
light winds, upslope flow may carry some smoke back to the east
again through evening. Smoke may also spread towards RDD per the
HRRR smoke loop.

The dry air mass will also result in strong radiational cooling over
the higher terrain and colder basins as well as the Valley. The dry
air mass precludes widespread heavy frost, although there is some
moisture in the ground from local watering.

Big question is will the cut-off low approaching the region next
week bring any chance of rain to Norcal. 12/12z GFS weaker and
farther south than the 12/00z ECMWF Mon/Tue next week yielding low
confidence in model solutions at this time.  JHM

.Previous Discussion...
A persistent upper level ridge which has been over the Eastern
Pacific moves inland today. A Red Flag Warning continues until 7 am
this morning over the mountains and northern Sacramento Valley
before gusty winds diminish. At 3 am, winds at Jarbo Gap were still
gusting to 38 mph. Winds will decrease through the day today as the
ridge axis moves across the area and the pressure gradient
decreases. Humidity levels will remain quite low, though, with a
gradual improvement this week.

Wildfire smoke continues to be an issue, with poor visibility for
some spots, and bad air quality. Latest HRRR smoke forecast
indicates smoke pushing north again later today and tonight as
northerly winds decrease and shift to southerly. Strong inversions
will keep smoke fairly confined to lower levels, with little wind
to clear things out. Because of this, periods of dense smoke will
be possible across the Valley at least for the next few days.
Try to limit outdoor activity and check on sensitive groups. Go to to or you local air quality district for more
information on air quality.

The region will remain under the influence of a persistent upper
ridge, resulting in no change in the dry weather pattern. Smoke
might help to keep temperatures cooler the next couple of days.
High temperatures will be in the 60s to mid 70s for the Central
Valley, with mostly 50s to 60s for the foothills and mountains.
Cold overnight temperatures are expected mainly over the Central
Sacramento Valley southward, with lows in the 30s and lower 40s.
Lows will be in the teens to mid 20s across mountain basin
locations. EK



Broad upper ridge forecast to continue across the region later in
the week maintaining dry weather with mild days and cool nights,
and no strong wind events are expected. Forecast guidance is
indicating the possibility of a pattern change as an upper trough
approaches the area late next weekend into early next week.
However, confidence in details remains low so have kept the area
dry for now.


Widespread MVFR likely across the entire Sacramento Valley by 00Z
Tuesday as northerly pressure gradients relax allowing smoke from
the Butte County wildfire fills the valley. Areas of IFR will
continue south of KCIC. VFR conditions elsewhere with local
northeast wind gusts to 30 kts lingering across the northern
Sierra Nevada until 20Z.


Red Flag Warning until 7 AM PST this morning for Northern
Motherlode From 1000 to 3000 Ft. Includes portions of Nevada-
Yuba-Placer-Amador and ElDorado Units-Northern Sierra Foothills
from 1000 to 3000 Ft. Includes portions of Shasta-Trinity and
Butte Units-Northern Sierra Including Lassen NP and Plumas and
Lassen NF/S West of the Sierra Crest (West of Evans Peak-Grizzly
Peak-Beckworth Peak)-Northern Sierra Including the Tahoe and
ElDorado NF/S West of the Sierra Crest-Southern Motherlode From
1000 to 3000 Ft. Includes portions of Calaveras-Tuolumne Unit-
Stanislaus NF West of the Sierra Crest.

Red Flag Warning until 7 AM PST this morning for Burney Basin
and Northeast Plateau in Shasta County Including Northwest
Lassen NF north of Lassen NP-Eastern Mendocino NF-Eastern
Portion of Shasta/Trinity NF-Lake County Portion of Lake-Napa-
Sonoma Unit-Northern Sacramento Valley to Southern Tehama County
Line Below 1000 Ft-Southeast Edge Shasta-Trinity NF and Western
Portions of Tehama-Glenn Unit.


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