Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 172327

Area Forecast Discussion
National Weather Service Sacramento CA
327 PM PST Sat Nov 17 2018

Dry with near to above normal daytime temperatures and cool
nights through early next week with smoke in the valley due to
the Camp Wildfire. Breezy northeasterly winds over the Sierra
Nevada tonight into Sunday bringing critical fire conditions.
Cooler temperatures next week with a series of wet systems the
middle to end of next week.


High pressure will remain over the region into next week. Little
change in conditions is expected through at least Monday. A weak
trough moving into the Great Basin today will increase the
offshore pressure gradient tonight and bring some breezy conditions
to areas north of I-80 overnight to increase fire danger. Smokey
skies will continue due to the light winds. Temperatures will
continue to be cooler than normal at night to near normal during
the day in the valley from the central Sacramento valley southward
to above normal for the north end of the valley, foothills and

Tuesday the ridge will begin to shift to the east and a trough
begins to approach the coast. This will reverse the wind
direction and bring southerly winds to the region that will help
to bring better dispersion of the smoke. Rain looks to start
Tuesday night along the coast spreading inland during the morning
hours on Wednesday.


A major pattern change is in effect for next week with a series of
wet storms from mid to late week as the persistent high pressure
ridge is finally displaced to the east. This will bring periods
of moderate to heavy rain to the area, though with some breaks at
times. This will likely cause travel problems due to wet roads,
local ponding on roads with clogged storm drains, and accumulating
snow in the mountains during the Thanksgiving travel period. The
first system could begin to spread in as early as Tuesday night,
spreading across the area by early Wednesday. Those planning to
travel should closely monitor the forecast to determine the best
times to drive.

Positive aspects of the change include beneficial help suppressing
current wildfires and improving air quality. This system should
provide winds to scour out existing smoke and reduce smoke
production by the Camp Fire. Wetting the ground and increasing
humidity should also inhibit future fires from developing.

Negative aspects of this pattern change are ash flow which could
occur near recent burn scars and there is even the potential for
debris flows if rain intensity is high enough. The best potential
at this point for heavy rain appears to be Thursday night into
early Friday, but timing could change as we get closer to the
event and forecasting intensity is difficult this far out.

Rainfall amounts could be several inches across the area, more in
the mountains. Accumulating snowfall could be significant through
the period, causing potential travel difficulties across the
passes during the busiest travel period of the year. Exact timing
and amounts remain uncertain, but could potentially total a foot
or more. EK



Widespread MVFR with local IFR likely to continue in the Central
Valley the next 24 hours as smoke from the Camp Fire persists. VFR
conditions elsewhere. Generally light winds at TAF sites, though
winds in the Sierra could locally gust to 30 to 40 kt bwtween 06
z and 18z. EK

Red Flag Warning from 10 PM this evening to 4 PM PST Sunday 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.


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