NWS Area Weather Forecast Discussion
County Warning Area [CWA]: STO Regional NWS Weather Office: Sacramento, CA
FXUS66 KSTO 242050
Area Forecast Discussion
National Weather Service Sacramento CA
150 PM PDT Sat Jul 24 2021
Dry weather with temperatures warming into the weekend. Chances
for mountain thunderstorms this weekend through next week.
High pressure building over the Desert Southwest is setting up
for a prolonged monsoonal moisture push into Northern California.
In the short term there may be an isolated shower or thunderstorm
later this afternoon around Alpine county southward along the
crest. Smoke from the Dixie wildfire has been slower to improve
over the interior than what the HRRR is suggesting but does have
it improving overnight and Sunday as it pushes the smoke towards
More moisture will arrive starting on Sunday but the big increase
will occur late Sunday night and Monday morning when we should see
a noticeable increase in cloud cover. Precipitable waters will be
high so any thunderstorms should have heavy rain associated with
them. Questionable time period will be Monday night through
Wednesday when there would be some potential for storms at lower
elevations. For now most of the activity is forecast to stay over
the mountains but that could change.
A decent Delta breeze will occur through Monday before becoming
lighter on Tuesday. Temperatures will trend cooler through Monday.
By Tuesday the low clouds along the coast will likely be getting
mixed out which in turn will lead to a weaker Delta breeze and
warmer inland temperatures.
.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)...
Wednesday there is an interesting feature that we will need to pay
close attention too. An upper level circulation will move
northward through the valley during the day. This time of year and
with the moisture that will be in place showers and thunderstorms
will probably have there greatest chance of getting into the
valley. For Thursday through the rest of the extending period the
monsoonal moisture gets pushed to the crest. There may be some
slight warming late next week then cooling over next weekend as
the high pressure weakens over the Desert Southwest.
VFR conditions are generally forecast to prevail over the next 24
hours except for areas of MVFR as a result of wildfire smoke
generally north of I-80 in the mountains and over the far north
end of the valley. Conditions should improve overnight in the
valley with a chance for the foothills improving Sunday morning.
Areas of smoke will also persist around Alpine county. Surface
wind gusts under 12 kts except local southwest gusts 20-30
kts vicinity west Delta.