FXUS66 KSTO 152302
AFDSTO
Area Forecast Discussion
National Weather Service Sacramento CA
302 PM PST Fri Jan 15 2021
SYNOPSIS...
Dry weather into next week with areas of late night and morning
valley fog. Well above average temperatures will continue into
next week. Strong winds possible early next week.
.DISCUSSION
...
Visible satellite early this afternoon is showing most of the fog
has dissipated across interior NorCal. High clouds can be seen streaming
through the north state as a weak shortwave moves along the flow.
The clouds will dampen temperatures in the northern Sacramento
Valley today. Temperatures across the Central Valley are forecast
to peak in the mid to upper 60s, which is still around 10 to 15
degrees above the daily normal. A few light radar returns are also
popping up with this shortwave over Shasta County and the northern
mountains. Some sprinkles may be possible, though rain
accumulation is not expected.
Strong high pressure builds over Northern California this weekend,
allowing temperatures to rise more. High temperatures are forecast
around 10 to 20 degrees normal this weekend with Valley and
foothill temperatures in the mid 60s to low 70s and mountain
temperatures in the upper 40s to 60s. Radiation fog is still
likely to form in the evenings into the mornings through Sunday
morning as overnight relative humidity values are forecast to
remain high.
Ensemble guidance continues to suggest an offshore wind event
late Sunday into Tuesday. A shortwave trough will slide south
down the coast Sunday into Monday with another wave of energy
sliding southwest from the Great Basin into Southern California
late Monday into Tuesday. North to east winds are expected to
increase with the first wave late Sunday night, remaining fairly
strong through Tuesday. At this point, the strongest Valley winds
are expected Monday afternoon and evening with stronger mountain
winds Tuesday. The NAEFS continues to show a band of anomalous
winds Monday into Tuesday, with 30+ year return intervals for
Monday afternoon over the Central Valley. More forecast details
can be found in the discussion below. -HEC
.EXTENDED DISCUSSION
(Tuesday THROUGH Friday)...
Models are coming into good agreement Tuesday will be a gusty day
for Northern California. An upper level closed low will push off
the Southern California coast early next week bringing gusty
offshore winds to California. Cluster analysis first started
picking up this feature in the synoptic pattern several days ago
and has continued to consistently hone in on the location and
timing of this closed low. Therefore, we can have some confidence
this will likely be an impactful wind event for California.
Areas
that typically see onshore flow, like the Delta, will see the
reverse, with strong offshore flow expected. These north to east
gusts could potentially cause tree damage and power outages.
Current forecast for Monday and Tuesday indicates wind gusts
ranging from 30 to 50 mph in the Valley, 50 to 60 mph in the
mountains, and gusts up to 70+ in favored gaps, canyons and
ridgetops. Weakened or burned trees and limbs may fall in strong
winds. A High Wind Watch has been issued for late Sunday night
through Tuesday for much of the Valley, foothills, and mountains.
Please stay informed with the lasted forecast updates as the
details of this event are still subject to change. Thereafter,
quiet weather is expected Wednesday into Thursday as models are
indicating a pattern change with a gradual cooling trend in to the
weekend. A low pressure system is forecast to possibly impact
northern california by next Friday and into the weekend. Stay
tuned for updates on this possible return of wet weather to
Northern California as we still have a lot of uncertainty this far
out in the forecast period.
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