Debris Flow and Flooding in California, February 6 to 8, 2025

Area Forecast Discussion
National Weather Service Sacramento CA
133 PM PST Wed Feb 5 2025

.SYNOPSIS...
A brief lull in precipitation today, ahead of a colder weather
system bringing widespread rain and major mountain snow and travel
impacts with gusty southerly winds. Drier weather with chances
for cold mornings return to the area this weekend and into early
next week.

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.DISCUSSION...
There's been a brief lull in the weather today, with some clouds
visibile in Shasta County and over the Coastal Range on GOES West
visible satellite imagery at 1pm, but not much else. Mostly clear
skies should continue into the evening, when cloud cover and
precipitation will begin to encroach across the remainder of
interior NorCal.

Early on Wednesday, rain and snow begin again. Precipitation will
start in the Coastal Range and Shasta County, but will spread
south and east over the course of the morning. Rain is expected to
be much lighter than the last couple of storms, with most Valley
locations seeing only a 20 to 55% probability of 48 hour rainfall totals
that are 1 inch or more. North of Redding, and in the foothills,
chances are slightly higher: generally 35 to 65%. Most of the
impacts for this storm, however, will be due to the expected snow.

Snow levels are expected to fluctuate a bit, with the Shasta
County mountains and Coastal Range starting around 2500 feet on
Thursday and rising to 4000 to 4500 feet overnight into Friday.
Later on Friday morning, snow levels will fall back to 2000 to
2500 feet again, though much of the snow will have occurred by
that point in the area. By the time snow begins in earnest in the
Sierra, snow levels will have risen to 4500 to 5000 feet. They
will continue to rise overnight, up to 600 to 7000 feet, before
falling again in the early hours of the morning to around 4000 to
5000 feet. All of this to say, we're expecting moderate to heavy
snow at times, above 3000 feet in Shasta County and the Coastal
Range, and above 5000 feet in the northern Sierra. There is a 20
to 40% probability of 8 inches or more of snow in the former area,
and 45 to 65% probability of 8 inches or more in the latter. As
such, we have issued a Winter Storm Warning for Shasta County
mountains and the Coastal Range above 3000 feet from 4am Thursday to
4am Friday, and for the northern Sierra above 5000 feet from 10am
Thursday to noon on Friday. In addition to snow in the Sierra,
winds will gust up to 50 to 60 mph, creating very difficult travel
conditions. Slippery and snow-covered roads, chain controls, and
significant travel delays are all expected so please exercise
caution if planning any mountainous travel.

Rain and snow will taper off Friday afternoon and evening, leaving
us with drier weather and cold mornings over the weekend.

&&

.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)...
While interior NorCal will still remain underneath the broad
influence of the departing trough on Sunday, drier weather is
expected through the weekend and into early next week, with breezy
northerly winds and cold temperatures being the primary weather
impacts expected for most of the extended forecast. Slightly below
normal high temperatures in the low to mid 50s are anticipated
for the Delta, Valley, and foothills, with 40s to low 50s at
higher elevations. Lows look to hover in the low 30s in the Valley
and foothills, with the mountains seeing single digits to teens.
Take time now to prepare for expected colder temperatures and be
sure to protect pets, plants, and people, especially those more
susceptible cold weather impacts.

On Wednesday, there is some disagreement between ensembles and
cluster analyses on whether we'll see a return to active weather.
Some solutions point towards more precipitation starting on
Wednesday, while others show a dry but windy pattern. Stay tuned
for updates to the forecast as we get closer to the middle of next
week.

&&

.AVIATION...
Mainly VFR conditions are expected with areas of IFR/LIFR
conditions after 00Z Thursday over Shasta County due to showers
and mountain snow. Precip will spread, bringing potential for
MVFR/IFR conditions to the remainder of the area by 12Z Thursday.
Snow levels are forecast to rise to around 4000-5000 ft in the
Shasta County and Coastal Range mountains, and 6000 to 7000 ft in
the N Sierra over the course of the day on Thursday. Snow levels
lower back to 2500 to 4500 ft by Friday morning. Surface winds are
forecast to be generally at or less than 12 knots in the Valley
and foothills, except in the N Sacramento Valley and adjacent
foothills where gusts up to 20 kts will be possible through 00Z
Thursday. Southwesterly winds are forecast to gust 25 to 35 kts
until 03Z Thursday in the mountains. Gusty southerly winds return,
up to 60 kts in the mountains, and 20 to 30 kts in the S
Sacramento and N San Joaquin Valleys, after 18Z Thursday.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning from 4 AM Thursday to 4 AM PST Friday for
Burney Basin / Eastern Shasta County-Mountains Southwestern
Shasta County to Western Colusa County-Shasta Lake Area /
Northern Shasta County-West Slope Northern Sierra Nevada-Western
Plumas County/Lassen Park.

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