Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 301127

Area Forecast Discussion
National Weather Service Sacramento CA
427 AM PDT Thu Mar 30 2017

Weak front will bring light rain and snow to norcal today with
lowering snow levels. Gusty north winds are likely Today and
Friday. Seasonably dry weather anticipated for Saturday with
chances for light rain over the mountains late Sunday and Sunday


IR satellite imagery shows back edge of weak frontal band moving
across the north coast at this time. Precipitation amounts across
the north state with this system have been quite light and
generally a tenth inch or less except over the Sierra were
orographics have squeezed out a few tenths. A shortwave trough
pivoting through southwest flow ahead of the front has brought
isolated thunderstorms southeast of Redding but this storm should
dissipate as it moves into the mountains. Any precipitation
threat should end by this afternoon as the upper low shifts into
the Great Basin except over the Sierra where rap around moisture
may bring a few lingering showers. Snow levels should drop from
over 8000 feet this morning to below 5000 feet this afternoon but
limited precipitation should limit impacts. Cooler airmass behind
the front will bring down daytime highs today to near normal for
this time of year. Northerly flow between upper low moving
eastward and upper ridging over the eastern Pacific will bring
breezy to gusty north winds across the north state. Surface
gradients this afternoon through Friday are forecast to run
between 8 and 10 mb. With surface gradients and upper level
support...breezy to gusty winds should continue most areas through
the nightime hours. Upper ridge axis pushes eastward to near the
coast by Friday afternoon bringing several degrees of warming and
fair skies for norcal. Still more warming is expected on Saturday
as the upper ridge shifts over the west coast. Daytime highs
should come in around 10-15 degrees above normal. Upper ridge axis
breaks down by Sunday allowing for a chance of precipitation
across the northern mountains by afternoon.


Ridging builds over the region Mon and Tue with temperatures
remaining around 5 degrees warmer than normal. A larger upper
level trough approaches the Pacific NW next Wed and Thu, bringing
a wetter Atmospheric River storm pattern. The probability of
Integrated Vapor Transport tool shows increasing confidence of a
steadily strengthening AR event . Right now the brunt of the
energy is still northward of 40 deg N and into Oregon, but the
last couple runs have trended farther south. This certainly grabs
our attention.      JClapp


Mainly VFR conditions with some isolated to scattered showers
through morning and possible MVFR conditions in Valley near
showers. LIFR conditions are expected in vicinity of showers.
Northerly Valley winds increasing to sustained near 15 kt by 12Z
and 20-25 kt after 18Z.      JClapp


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