Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 211651

851 AM PST Fri Nov 21 2014

The next weather system moves through NorCal late today into
Saturday bringing widespread precipitation. High pressure builds
over the area next week for generally dry weather and milder
daytime temperatures along with areas of morning valley fog.


.Update Discussion...
Forecast for today on track with only minor tweaks to this
morning`s sky cover and POPs this afternoon. Areas of fog will
linger this morning but visibilities have started to improve over
the last several hours. Latest hi-res guidance suggests precip
will hold off until 18-19Z in the far NW before rain overspreads
the rest of the area tonight into Saturday. Latest QPF values
range from 0.10-0.4" in the valley to 0.5-1.5" in the foothills
and mountains. Snow amounts will be limited as snow levels will
rise above 7000-8000 ft as system moves in tonight. CEO

.Previous Discussion (Today through Monday)...
With the second system now existed, low clouds and fog hamper
visibility in the Central Valley and up into Clear Lake area this
morning. The clouds had already set up last night before any major
fog. The clouds act as a blanket to keep the temps from dropping
very much, so getting widespread dense fog may be difficult.
However, satellite is showing some breaks in the cloudiness which
would lead to denser fog.

The next system which is more of a plume of moisture embedded in
strong jet stream energy will streak across NorCal tonight and
Saturday. This system has the deeper moisture with precipitable
water values 1.00-1.50 inches. Rainfall amounts will range from
.10-.60 for valleys and 0.75-1.50 inches for the mountains,
beginning late today up north and spreading southeastward
tonight. Snow levels will be high with this warm system starting
around 6500 feet...but rising to 7500-8000 feet after midnight
tonight. Only an inch or two of snow will fall at highest
elevations, except 5-7 inches over Lassen Peak.

Ridging and northwest flow will develop on Sunday into Monday
with drying conditions. temperatures will remain near normal.

.Extended Discussion (Tuesday through Friday)

All models in agreement that ridging will dominate NorCal with
dry, mild weather into Thursday. Patchy fog is possible in the
early morning hours as moisture left over from the recent storms
and cold overnight lows could allow for fog development. Daytime
afternoon highs will be nice and warm (about 4-10 degrees above
normal) for our region.

On Friday, the models diverge a bit and there could be a slight
chance of light precipitation moving into the coastal range and
northern mountains.



A mix of LIFR/IFR/MVFR early this morning with ceilings and
visibilities after yesterday`s weather system. Satellite shows
some areas of patchy fog/low clouds in the valley and delta. It
also shows some high clouds just offshore that will stream across
NorCal this morning. Those high clouds may help break up the low
clouds. Conditions will improve by late morning into afternoon.
The next wave precipitation into interior Norcal will be later
today with the bulk of rain/snow occurring after 4 pm. This will
bring widespread MVFR with local IFR cigs/vsbys across NorCal
into Saturday. Light winds for much of today, but southerly winds
will increase ahead of tonight`s frontal passage.


.STO Watches/Warnings/Advisories...

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