Grass Valley, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

865
FXUS66 KSTO 282047
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1247 PM PST Sat Dec 28 2024

.SYNOPSIS...
Active weather will bring rain, mountain snow, and breezy to
gusty southerly winds into the weekend. Drier weather is expected
into next week with colder morning lows and patchy Valley frost
and fog.

&&

.DISCUSSION...
Most of the rain shower activity has been confined to Shasta
County, especially in Redding, this morning and early afternoon.
24-hour rainfall totals at Redding AP are around 0.75 inches, with
the bulk of the rainfall falling overnight and through this
morning. Current Radar analysis shows lingering showers in the
northern Sacramento Valley, although most of the heavier
precipitation has moved out of our area. Snow levels still holding
above pass levels today; above 8000 feet. Chances for precip will
continue, mainly in Shasta County and the foothills and mountains
for the rest of the day before the next wave of widespread
precipitation moves into the region late tonight/early tomorrow
morning.

The final wave of precipitation from the series of storms will
move into the area late tonight into tomorrow morning, bringing
renewed rain shower chances for the Valley. Once again, the better
chances for rainfall will be in the northern Sacramento Valley,
southern Cascades, the northern Sierra and adjacent foothills.
Current storm total rainfall forecasts have around an additional
1-2.25" inches of rainfall in the aforementioned areas. Snow
totals have come up again for the southern Cascades and northern
Sierra, we could see around a foot of snow along the peaks, and
around 5 to 10 inches at 6000 feet. As more of the Hi-res, short-
term models have come in this morning, the NBM has adjusted the
snow totals up, however even with the forecast snow total
increase, impacts are expected to remain at Advisory levels. Gusty
southerly winds will also develop early tomorrow morning through
the evening. Southerly winds of 15 to 25 mph, with gusts up to 45
to 50 mph expected. Strongest winds will be in the
northern/central Sacramento Valley and Foothills. A Wind Advisory
will go into effect 10 PM this evening through 2 PM tomorrow.
There is also a marginal chance (10-15%) of t-storms in the Valley
and foothills tomorrow morning/afternoon.

The progressive nature of this final push of moisture will limit
flash flooding concerns, however there may be ponding of water on
rises on local waterways as we move into Monday. We begin to clear
out Monday as upper level ridging develops over the region.
Northerly winds will develop Monday afternoon, with gusts of 15-25
mph possible, especially along the wind prone area of I-5 and the
western Sacramento Valley. In addition to the drying,
temperatures will cool, and lead to frosty and potential foggy
mornings. The NBM is still highlighting around a 30-60% chance of
Valley lows dropping below 35 degrees Tuesday-Thursday.


.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)...

Ensemble guidance continues to indicate upper level ridging
remaining in place until late next week. Foggy and potentially
frosty mornings will remain in the forecast until at least Friday
AM. Clusters then show ridging breaking down by Friday as a PacNW
trough digs into far NorCal. NBM probabilities have changed little
regarding a chance for wetting rains Friday through Saturday, with
the best chances remaining in the northern Sacramento Valley
specifically in Shasta County. Valley high temperatures will be in
the 50s to around 60 degrees or so during the extended period.
Overnight low temperatures will climb into the 40s by Thursday.
&&

.AVIATION...

Areas MVFR/IFR with local LIFR in low ceilings and/or
precipitation next 24 hours. Scattered precipitation generally
north of I-80 through 06z Sunday, becoming more widespread after
10z Sunday. Isolated thunderstorms across portions of the Valley
and foothills 18z Sunday - 00z Monday. Snow levels 6500 ft early
Sunday morning, falling to 5000-6000 feet after 15z-18z Sunday.
Southeasterly wind gusts 15-25 kts across portions of the Valley
through 03z Sunday, increasing up to 30-45 kts 03z-22Z Sunday.
Over mountains, areas of southwest to west surface wind gusts to
35 to 55 kts 03Z Sunday to 00z Monday.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 10 PM this evening to 2 PM PST Sunday for
Central Sacramento Valley-Northeast Foothills/Sacramento Valley-
Northern Sacramento Valley.

Winter Weather Advisory from 5 AM to 8 PM PST Sunday for West
Slope Northern Sierra Nevada-Western Plumas County/Lassen Park.

&&

$$