Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 231054

Area Forecast Discussion
National Weather Service Sacramento CA
354 AM PDT Fri Mar 23 2018

After a brief break, wet weather will return by tonight and
continue into the weekend. Snow levels will lower with
significant snowfall accumulation expected into the weekend.


What a difference 24 hours makes. The mild airmass with deep
moisture has been shunted to the south and east by yesterday
afternoon`s cold front replaced with a colder and drier airmass.
Current temperatures are running 10-20 degrees cooler compared to
24 hours ago, and DP`s are running 15-30 degrees lower.

The break in precipitation overnight won`t last too much longer.
Showers will develop across the northern portion of the forecast
area by midday as the next system drops down from the Gulf of
Alaska. The next cold front will drop south tonight bringing
showers to the Sacramento region and renewed snowfall to the
northern Sierra Nevada. Ahead of it, gusty southerly winds will
increase across the region today.

That will be followed by a second even colder system which will
move southward Saturday afternoon and night. A few thunderstorms
will be possible Saturday afternoon across the northern Sacramento

Snow levels will lower to around 1500 feet in Shasta County and
3000-4000 feet in the northern Sierra Nevada by Saturday. With the
cold and convective nature of these systems, snow ratios will be
much higher than the past several days. Heavy snow is likely with
1-3 feet of fresh accumulation across the mountains, and a winter
storm warning has been posted with significant travel impacts

Diminishing showers are expected by Sunday night as the trough
shifts into the interior West and ridging from the eastern Pacific
begins to edge onto the West Coast. Gusty north winds and milder
temperatures are expected Monday.


Upper level high pressure building over the eastern Pacific and
west coast will bring fair skies, warmer than normal temperatures
and light northerly breezes by the start of the extended period
next Tuesday. Temperatures will continue to warm Wednesday and
Thursday as the upper ridge centers over the west coast and the
airmass over Norcal warms. By Thursday afternoon, daytime highs
will warm to 10 or more degrees above normal some areas. The upper
ridge is forecast to weaken slightly next Friday as a weak system
passes to the north. This will bring a slight drop in daytime
temperatures but highs will continue to run well above normal.


Mainly VFR conditions this morning. Rain and Snow showers
spreading southward this afternoon and tonight with MVFR/IFR
conditions northern Sacramento valley after 00z Saturday.
deteriorating conditions spreading southward to the northern San
Joaquin valley by 12z Saturday. Snow levels 2500 to 3500 feet.
Southerly winds increasing after 18z with gusts 25 to 35 knots
areas north of KSAC.


Winter Storm Warning from noon today to 6 AM PDT Sunday for
Burney Basin / Eastern Shasta County-Clear Lake/Southern Lake
County-Mountains Southwestern Shasta County to Northern Lake
County-Western Plumas County/Lassen Park.

Winter Storm Warning from 6 PM this evening to 9 AM PDT Sunday
for West Slope Northern Sierra Nevada.

Winter Storm Warning from 9 AM this morning to 9 AM PDT Sunday
for Shasta Lake Area / Northern Shasta County.


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