Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 271012
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
312 AM PDT Mon Oct 27 2014
Continued mild weather through Thursday. Then a frontal system
impacts northern interior California Friday (Halloween) and
Saturday with a good probability of rain.
.Short Term Discussion (Today through Thursday)...
Broad, flat ridging dominates with mid to high clouds filtering
the sunshine today into Wednesday with a weak disturbance
struggling to bring only a slight chance of light rain into
western Shasta County on Tuesday and Wednesday. Temperatures will
rebound into the mid to upper 70s in the Valley and 50s to low
70s in the mountain and foothills.
A good, dynamically sound frontal system strengthens in the
eastern Pacific by Thursday. In response to this, the
trough/ridge couplet amplifies and shifts east with the ridge
axis over the western Great Basin. This still translates to mild
weather for interior northern California with increasing clouds
on the horizon and stronger upper elevation winds.
.Extended Discussion (Friday through Monday)
Confidence continues to increase that we`ll see a significant
winter-like system affecting the region Halloween into Saturday.
Timing of the initial frontal system moving inland has improved
with the 00Z Monday operational runs of the GFS, EC and GEM
pointing toward daytime Friday for the onset of precipitation with
showers continuing Friday night and Saturday as the upper trough
moves overhead. Moderate amounts of precipitation, gusty winds and
potentially significant amounts of snowfall for the higher
elevations of the northern Sierra will be possible with this
Trough shifts east Sunday with ridging forecast to return into
early next week leading to a return of dry northwesterly flow for
much of interior NorCal and a retreat of precipitation chances to
around the Oregon border.
Flat ridge moves over NorCal next 24 hours resulting in general
VFR conditions. Occasional periods of high clouds will move
through the area.