Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 271636

936 AM PDT Sat Sep 27 2014

Cool weather with lingering showers or thunderstorms possible,
mainly over the Sierra Cascade range, through this weekend. Dry
and warmer next week with locally breezy north wind around mid week.


Higher resolution models indicate moisture will wrap-around the
closed low moving from central CA into Wrn NV today. Several tenths
of an inch of QPF is forecast along the deformation zone set up over
the Siernev this afternoon into this evening. This is expected to
result in several inches of additional/new snow accumulations as
indicated by the NAM/GFS snow accumulation progs. Snow levels will
be near/above 8 kft so only the higher passes south of HWY 50 will
primarily be affected. WSW was issued in the morning update for the
first and early season snowfall.

Marginal instability forecast over the Siernev this afternoon into
the evening with potential for isolated to perhaps scattered
thunderstorms. Although cloud cover will limit heating...moderate
shear and strong cyclonic flow along the deformation axis could
result in some thunder over the crest from Plumas county southward.

.Previous Discussion...

Not looking for a lot of change in daytime temperatures
today with highs remaining several degrees below normal under a cool
airmass. The upper low continues eastward on Sunday but Sierra
Cascade range remains under cyclonic flow and some instability.
Showers will again be a possibility here but likely remaining at the
higher elevations as the low moves east. Less cloud cover should
allow for just a bit of warming on Sunday. A small high pressure
ridge pushing inland behind the low and over the southwest U.S. on
Monday will bring an end to any shower threat, clearing skies and
the beginning of a warming trend. The ridge will be knocked down
temporarily by another low pressure trough but this time moving
inland well north of the region. The main impact of this system will
be a slight cooling effect Tuesday and a few clouds over the far
northern CWA.

.Extended Discussion (Wednesday through Saturday)

Models in good agreement in building a strong ridge of high
pressure over the west coast Wednesday on through next weekend.
Daytime highs will start out around normal on Wednesday then
continue to climb through the end of the week. Surface high
pressure pushing into the Pacific Northwest on Wednesday will
bring a period of breezy north winds Wednesday into Thursday for
much of the CWA. Lighter winds are expected by the end of the week
as the upper ridge centers over the west coast and surface
gradients relax.



Scattered showers and isolated thunderstorms will continue during
the next 24 hours over the northern Sierra Nevada with local MVFR
conditions possible at times. Elsewhere, VFR conditions expected
through 12Z Sunday.


.STO Watches/Warnings/Advisories...
winter weather advisory for snow until 11 pm pdt this evening
above 8000 feet over the west slope northern sierra nevada.


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