FXUS66 KSTO 181055
AFDSTO
Area Forecast Discussion
National Weather Service Sacramento CA
355 AM PDT Fri Sep 18 2020
SYNOPSIS...
Weather system moves across NorCal today bringing a few showers to
the foothills and mountains along with cooler temperatures and
locally breezy to windy conditions. Warmer and drier weather
returns for the weekend into next week.
.DISCUSSION
...
Clear to partly cloudy skies cover NorCal early this morning as
the mid/upper front pushes gradually to the southeast across the
region.
Areas of south to southwest wind gusts in the 20s and 30s
mph have been occurring across the foothills and mountains, while
southerly gusts in the teens to lower 20s mph have been common
across the northern Sacramento Valley. The southerly breezes have
brought a return of good AQI has throughout the Sacramento and
northern San Joaquin Valleys.
Moisture from the remnants of Karina continues to move up from
the southwest into central California, and radar has been
indicating a few light showers at times across the far southeast
corner of the forecast area.
Upper trough moves across the area this afternoon. Some light
showers will be possible into this evening across the northern
Coast Range and northern mountains, and a few showers will likely
continue into the afternoon across the foothills and northern
Sierra south of Lake Tahoe as the front moves through and
interacts with the Karina moisture. Thunderstorm threat likely to
remain well to the north of the region.
Strong gusty southwest winds will be likely today across the
higher ridges of the northern Sierra as the front gradually works
its way south. Locally breezy southerly winds likely to continue
elsewhere. High temperatures today expected to be around 10-15
degrees cooler compared to Thursday`s.
Warmer and drier conditions return over the weekend as ridging
returns. Generally light north winds likely Saturday into early
Sunday, but surface gradients will be much weaker than previous
recent events.
.EXTENDED DISCUSSION
(Tuesday THROUGH Friday)...
Warm and dry pattern early next week under zonal flow. Ridge then
amplifies into Wednesday, resulting in a slight warming trend.
Near normal temperatures are expected through Thursday, with
Valley highs generally in the mid 80s and low 90s. Models have
moved away from their deeper trough solution late next week. Thus,
confidence is low in terms of breezier conditions and how much
cooling is anticipated. At this point, most of the moisture would
appear to be confined to far northern CA but timing is uncertain.
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