Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 211050

Area Forecast Discussion
National Weather Service Sacramento CA
350 AM PDT Wed Mar 21 2018

Wet weather continues into the weekend. Snow will remain above
pass levels through most of tonight, then will lower with
significant accumulations possible at the higher elevations.


Initial wave moved through late Tuesday and earlier in the night
with most of the region receiving between 1/4 and 3/4`s of an
inch of rain. Areas of mostly light to moderate precipitation
continue in the warm air advection environment. Snow level radars
at Chico and Colfax indicate the snow level remains above 8000
feet. Current temperatures are very mild ranging from the upper
30s and 40s in the mountains to the upper 40s to mid 50s across
the Central Valley.

Off and on light precipitation will continue across the valley
today, though there will be conditional threat for some
thunderstorms by mid-afternoon that will be accompanied by heavy
rain and gusty winds. Forecast soundings indicate a lower-level
cap which may be overcome with enough surface heating (if there
are any breaks long enough to allow for it), but sufficient
elevated CAPE (250-500 j/kg).

Precipitation expected to increase across the region tonight into
early Thursday as the surface front approaches and moisture
transport from the south increases. Much of the valley expected to
see around an inch of rain with 2-4 inches over the mountains
where orographic enhancement will increase. Have decided to let
the Winter Storm Watch continue for now as it`s looking more
likely that snow levels will remain high into Thursday. Winds will
also increase across the area.

Strong cold front will sweep southeast around midday with snow
levels lowering rapidly in its wake during the afternoon. As
mentioned above, confidence in the exact timing of frontal
passage and lowering snow levels is not high at this time and some
changes to details are likely. Travel is likely to deteriorate
rapidly later in the day as this change over occurs. Stay tuned
to the latest forecasts updates.

Thunderstorms possible again Thursday in the dry slot behind the
front. Brief heavy rain and small hail likely the primary
concerns. Over the northern Sierra, a relatively quick shot of
heavy snow will be possible into the evening before precipitation

A brief break in the wet weather looks possible late Thursday
night and Friday morning before a colder system brings potential
heavier snow to the mountains Friday into Saturday.


Main upper trough shifts east of the state during the day on
Sunday bringing the last of the precipitation for a while as upper
ridging builds over the eastern Pacific. Precipitation chances
will mainly be restricted to east of the central valley.
Precipitation amounts will be quite light but snow levels will be
abnormally low at around 1500 to 2500 feet. A few lingering
showers may still be possible Sunday night but building high
pressure will bring an end to any precipitation threat by Monday.
Temperatures warm by several degrees on Monday but are still
forecast to run slightly below normal. Upper level and surface
gradients indicate breezy north winds which will help to start
drying things out. Temperatures continue to warm on Tuesday as
upper ridge pushes inland with highs expected to warm to several
degrees above normal. Even more warming is expected on Wednesday
with highs throughout the valley expected to reach the mid 70s in
the northern Sacramento valley. Breezy north winds will continue
through the period between an upper low over the southwest U.S and
building high pressure over the eastern Pacific.


Mainly MVFR/IFR conditions next 24 hours TAF sites as Pacific
storm system pushes through the region. Mainly IFR over mountains.
Snow levels 6500 to 7500 feet. Southerly wind increasing after
00z Thursday with gusts to 25 knots northern Sacramento valley to
45 knots over the higher Sierra.


Winter Storm Watch from this evening through Thursday evening
for West Slope Northern Sierra Nevada-Western Plumas
County/Lassen Park.


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