FXUS66 KSTO 180332
AFDSTO
Area Forecast Discussion
National Weather Service Sacramento CA
832 PM PDT Sat Apr 17 2021
SYNOPSIS...
Dry and warm weather through Monday. Temperatures will rise to
the upper 80s to low 90s by Sunday for Valley communities. Despite
the warm air temperatures, area waterways will continue to run
cold. Cooler weather possible by middle of next week, with the
chance of some mountain showers.
.DISCUSSION
...
Evening update: North/northeast winds in the Sacramento Valley
today brought relative humidity values way down -- even lower
than forecast. A sampling of minimum relative humidity values this
afternoon include 6 percent at Sacramento Exec Airport, 7 percent
at Sacramento Int`l Airport, and 7 percent at Chico. A combination
of the upper level ridge, dry soils, lack of moisture in the air,
and the katabatic/downslope winds allowed temperatures to soar
well into the 80s for many Valley locations. Sacramento Executive
Airport reported with one of the hottest readings at 89 deg F.
Record high for the day was 90 deg F, so just shy of matching
that. More of the same expected for Sunday afternoon, though some
locations may add several degrees on top of today`s highs. // Rowe
.PREV DISCUSSION
...
High pressure will strengthen over the region through Sunday.
Temperatures will warm into the upper 80s for most places with
some of the warmer spots reaching the lower 90s. Winds this
afternoon will decrease this evening in the valley and are
expected to stay light northerly on Sunday. Easterly winds in the
mountains will increase again tonight with some local gusts around
45 mph for some of the favored wind prone areas before decreasing
Sunday morning.
Lighter winds with little change to some minor cooling for the
daytime high temperatures are expected on Monday. We should see an
increase in winds late in the day in the Delta that should
persist through at least the evening hours as well.
Tuesday a low pressure system will begin to move into the far part
of the state. Some showers and maybe a few mountain thunderstorms
may be possible with the best chances over the Southern Cascades
south through Plumas County. This will also be the start of a
noticeable cooling trend. Winds through the Delta should be
stronger and persist throughout the day.
.EXTENDED DISCUSSION
(Wednesday THROUGH Saturday)...
No significant changes to the extended forecast. Ensembles and
clusters continue to indicate weak trough with varying degrees of
depth extending from the Great Basin region into Central
California Wednesday. Will maintain NBM`s idea of light shower
chances over the Sierra, but dry for Valley locations. A pattern
like this will likely have limited moisture and be dependent on
higher elevation instability. Heights will not be overly low in
this pattern allowing Valley high temperatures to warm into the
low 80`s.
Ensemble guidance shifts trough into the Desert Southwest
Thursday and Friday with drier and warmer conditions returning,
as ridge builds back overhead. Extended ensembles indicate
possible unsettled pattern heading into next weekend, but will we
will see how this evolves over the next few days.
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