Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 020437
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
937 PM PDT Wed Apr 1 2015

.Synopsis...
An upper trough will bring a slight chance of showers to the
northern mountains this evening, then breezy north winds tonight
into Thursday. A stronger trough will bring better chances of
rain and snow Saturday night into early next week.

&&

.Discussion...
The tail end of a trough is moving through California with some
light showers near the crest of the Sierra still lingering this
evening. The showers will continue to diminish through the
evening hours.

A northerly pressure gradient will be increasing overnight. Winds
will likely become breezy over the far north end of the valley
and along parts of the west side of the valley. On Thursday with
the system well east of us windy conditions look likely over the
valley with a possible wind advisory being needed. Northerly wind
gusts 25 to 35 mph look possible from around Red Bluff south and
into the Northern San Joaquin valley. The strongest winds look to
occur over the Southern Sacramento valley and Northern San Joaquin
valley.

Weak ridging building into the area Thursday night will help to
diminish the winds during the evening. The ridging will lead to
warmer temperatures for Friday with weaker winds. Another trough
setting up in the Gulf of Alaska for this weekend will start to
break down the ridge on Friday and reverse the wind flow in the
valley.

On Saturday a trough will deepen along the coast to bring some
clouds and a little cooler temperatures to the interior. The rain
looks like it will hold off during the day. The current timing for
when the wet stuff arrives is pointing towards late at night and
Sunday morning. Lowering snow levels will bring snow well below
Sierra pass levels on Easter.

&&


.Extended Discussion (Sunday through Wednesday)

A large low pressure system progged to drop southeast from the Gulf
of Alaska will approach the region by Saturday night. As system
rotates inland, two waves will impact the local area. Models in
decent agreement with general details but still differ a bit in
timing and precip amounts. Regardless, two rounds of precipitation
look likely, first from late Saturday night into Sunday and second
on Tuesday. Early estimates of precip amounts range from 0.25 to
an inch in the valley/foothills and upwards of an inch in the
mountains. Could see locally higher amounts if any thunderstorms
do materialize. Model fields suggest this is possible with a bit of
instability accompanying each wave.

Given the origins of the system, cooler air will accompany each
wave. This will drop snow levels below major pass levels with
accumulations likely above 4000 feet. A few inches possible with
first wave Sunday with higher snowfall rates expected on Tuesday.
Total accumulations could be around a foot at higher elevations.
Will be a system to watch as snow will likely impact Sierra
travel. Heightened concern due to lack of recent storms and
complacency of trans-Sierra travelers this late in the season. Details
will be further refined as we head toward the weekend. Cooler
temperatures (more near normal) will accompany this system as
well.

Ridging will build back in behind this system with a return to dry
weather for mid week.

CEO

&&

.Aviation...

VFR conditions thru the forecast period. Skies will generally
remain mostly clear. Breezy northerly winds will continue with
some gusts AOA 20 kts possible.


&&

.STO Watches/Warnings/Advisories...
None.
&&

$$







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