Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 190915
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
215 AM PDT Tue Mar 19 2024

.Synopsis...
Dry and warm weather will continue until Friday. Widespread rain,
high elevation snow, and cooler weather return as we move into the
weekend.

&&

.Discussion...
Upper level ridging dominates the synoptic pattern over interior
NorCal. Unseasonably warm temperatures will continue today with
highs in the mid to upper 70s for Valley locations with 50s to 60s
for the Foothills and higher elevations. While there will be some
instability developing later this afternoon/evening, mainly from
afternoon heating, the upper level high pressure/ridge should
suppress deep convection from developing. A shower or two in the
Sierra, mainly south of I-80, cannot be completely ruled out today
in the afternoon and evening hours.

Ridging begins to break down and weaken as we move into Wednesday,
which will allow for high temperatures to return to closer to
normal. A few late-afternoon showers may be possible, mainly in
Shasta County north of Redding cannot be ruled out on Wednesday
and Thursday as our upper level pattern shifts into more of a
westerly component. As we move into Friday, an upper level low
located in the PacNW will begin to move east and bring more
widespread precipitation chances to the area, beginning Friday
morning. Precipitation will begin along the Coastal Range then
spread throughout the region as we move into the late
morning/afternoon hours. Heaviest precipitation is expected late
Friday, along with a 10-20% chance of thunderstorms to develop in
the Valley, Foothills and the Sierra. Snow levels will be at
around 6000-7000 feet Friday, with National Blend of Models (NBM)
projecting around a 30-50% probability of 4" inches of snow or
more above 6000 feet on Friday in the Sierra. Rain showers and
mountain snow showers will continue as we move into the weekend,
as our region will be under a troughing pattern into next week.

&&

.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)...
As mentioned above, NorCal will be under a troughing pattern as
we enter the extended period. Periods of Valley showers and
mountain snow showers are expected to continue through Tuesday.
Overall, a general 0.25" to 1.25" inches of rainfall is forecast
for the Valley, with higher totals of 1-3" inches expected in the
Foothills and mountains. A 10-25% probability of thunderstorm
development also exists on Saturday afternoon/evening for the
Valley and Foothills. Snow levels on Saturday will be around
4000-5000 feet, lower to 3500-4500 feet on Sunday, then climb back
up to 4000-5000 feet on Monday and Tuesday. Forecast snowfall
accumulation is around 1-2 feet for elevations higher than 6000
feet from late Friday into Monday morning, with around 3-8 inches
at 5000 feet forecast. Latest QPF runs from the NBM have brought
snow totals down, so forecast uncertainty on totals remains high.
Lingering showers and mountain snow showers are possible as we
move through Monday and Tuesday, although little additional
accumulations are expected.

High temperatures will fall into the low to mid 60s for the
Valley through the extended, and higher elevations will be in low
30s to upper 40s. By Tuesday evening, upper level ridging is
forecast to build back in over the region and reduce precipitation
chances for the region. Clusters are fairly consistent in showing
ridging developing off-shore late Tuesday, however there is
disagreement on location of the ridging and magnitude at this
time.

&&

.AVIATION...
VFR conditions next 24 hours. Surface wind gusts less than 12 kts
except vicinity west Delta southwest 15-25 kts, strongest after
00Z Wednesday.

&&

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

&&

$$


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