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000
FXUS66 KSTO 220915
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
215 AM PDT Mon Apr 22 2024

.Synopsis...
Warm and dry weather continues today. Cooler temperatures return
Tuesday along with a chance for a few late day showers and
thunderstorms over the mountains. Precipitation chances increase
Friday as a weather system moves through, best chances in the
foothills and mountains.

&&

.Discussion...
Mainly clear skies and very mild temperatures persist over the
region early this morning. Current readings range from the upper
30s to mid 40s in the colder mountain valleys to the 50s over the
mountain ridges, and upper 50s to around 70 across the Central
Valley. Surface pressure gradient is a little more offshore
compared to 24 hours ago though most winds are generally light
except for some local northerly gusts of 15-25 mph over the
northern mountains.

Warm and dry weather will continue today as the upper ridge begins
to shift east. Offshore surface gradient will result in locally
breezy north to east winds of 15-25 mph in the Sacramento Valley
and surrounding terrain this morning. Highs today will be similar
to Sunday`s with mid to upper 80s across much of the Central
Valley with a chance that a few spots may reach 90 for the first
time this year.

The offshore trough approaches and displaces the ridge to the
east beginning Tuesday, and the combination of synoptic cooling
and the return of onshore flow will bring significant cooling to
the region with highs returning to around average during the
middle of the week. Southwesterly breezes will also return,
especially for the Delta and over the mountains.

Most of the energy with the incoming trough is headed toward
SoCal, but enough moisture/instability is forecast to be drawn
northward for a chance of late day showers and thunderstorms over
the northern mountains and northern Sierra during the middle of
the week, and a few of these may migrate down into the northern
Sacramento Valley.

&&

.EXTENDED DISCUSSION (Friday THROUGH Monday)...
On Friday, a secondary trough moves down from the Pacific
Northwest and along the eastern edge of California. This will
bring showers and instability, though it will primarily be focused
in the northern Sacramento Valley, foothills, and mountains.
Light but widespread showers are expected to occur in these
locations, with a 10 to 55% probability of at least a quarter of
an inch falling on Friday. There is also a 20 to 25% probability
of isolated thunderstorms, which would bring higher localized
rainfall totals. Additionally, some isolated thunderstorms in the
remainder of the Valley cannot be ruled out on Friday afternoon
and evening (10 to 20% probability, with increasing chances moving
northward or eastward). Finally, the uncertainty associated with
this system truly shows in the change in probabilities for snow at
higher elevations on Friday. Snow totals have trended down with
this most recent NBM run, showing only a 5 to 30% probability of
an inch or more north of HWY 50, and a 10 to 30% probability of 2
inches or more south of HWY 50. Highest peaks may see a few more
inches than this, though any higher totals will be highly
localized. Additionally, as stated in previous discussions, there
is still uncertainty associated with this system, so check back in
periodically for updates.

A brief, weak ridge will move over the area on Saturday and Sunday,
nudging temperatures back up to seasonable levels through early next
week. Early next week, a low pressure system centered over the
Pacific Northwest will keep Valley temperatures from reaching to
high above the high 70s; in general though, temperatures across the
region will remain near to slightly above normal, rather than
cooling. Other than that, conditions will be primarily dry and calm,
though chances for breezy northerly winds begin on Monday
afternoon. //SP

&&

.AVIATION...
VFR conditions next 24 hrs. After 00Z, southwest surface wind
gusts 15-25 kts develop in the west Delta, and local southerly
gusts 10-15 kts in the Sacramento Valley (northwesterly in the
northern San Joaquin Valley).

&&

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

&&

$$