137
FXUS66 KSTO 162049
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
149 PM PDT Fri Aug 16 2024

.SYNOPSIS...
Near to slightly below normal temperatures are expected to persist
into next week. A quick moving system on Saturday will introduce a
period of gusty winds to the region and a chance for isolated to
scattered showers and thunderstorms to portions of the northern and
central Sacramento Valley Saturday afternoon and evening as well.

&&

.Discussion...
As of early this afternoon, outside of a handful of isolated cumulus
at higher elevations, clear skies persist across interior NorCal.
Sunny skies and generally light south to west winds are expected to
prevail through the remainder of the day. This will help high
temperatures rise a few degrees through the afternoon, generally
settling in the 90s across the Valley and foothills, with 70s to 80s
at higher elevations.

Moving into the weekend, a robust closed low currently churning off
the coast of the Pacific Northwest looks to deepen southward toward
the northern California coast as a subtle shortwave travels through
the flow pattern. The proximity and magnitude of the deepening low
looks to induce a period of gusty winds on Saturday. In general,
wind gusts of 20 to 30 mph are anticipated across the region
tomorrow afternoon and evening, with current probabilities of gusts
exceeding 30 mph sitting around 50% to 80%, primarily in the
northern and central Sacramento Valley. An appreciable cool down is
anticipated on Saturday as a result, with high temperatures expected
to fall to around 5 to 10 degrees below normal.

Additionally, a batch of mid level moisture associated with the
aforementioned shortwave is expected to advect inland across
northern California on Saturday as well. With ample upper level
support, isolated to potentially scattered showers and thunderstorms
will be possible, generally from the I-5 corridor westward in the
northern and central Sacramento Valley, in the afternoon and evening
hours. Current probabilities of thunderstorm development are around
15% to 30% in this area, with highest probabilities west of the I-5
corridor at this time. Nonzero thunderstorm probabilities are still
present for portions of Shasta and Tehama counties east of the I-5
corridor, but generally remain less than 10% at this time. Primary
hazards with any thunderstorms that do develop will be brief heavy
rainfall, gusty winds, and lightning.

As the shortwave rapidly progresses northeastward through the flow
pattern, the closed low then looks to retreat further northward
toward the Pacific Northwest coast. While a slight warm up is then
expected on Sunday and Monday as a result, high temperatures still
look to remain below normal across the region into the week ahead.
With comparatively weaker onshore flow also expected within this
regime, a slight drying trend is also anticipated, with daytime
minimum humidity falling back into the upper teens to 20s by
Monday.

&&

.EXTENDED DISCUSSION (Tuesday THROUGH Friday)...
Cluster analysis continues to show very strong agreement on the
closed low remaining blocked in the vicinity of the Pacific
Northwest by robust ridging over the central CONUS through the
week ahead. Temperatures will likely fluctuate somewhat day to
day, remaining dependent on the strength and orientation of the
closed low as it remains nearly stationary. As a result, there is
a signal for a slight midweek warming trend to near normal high
temperatures, with a gradual downturn toward slightly below normal
temperatures through the end of the week. Otherwise, dry
conditions are anticipated throughout the long term alongside
periodically breezy winds in the afternoon and evening.

&&

.AVIATION...
VFR conditions next 24 hours. Surface wind gusts generally less
than 12 kts, except in the vicinity of Delta with gusts to 25
kts possible.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$