Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 192237
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
337 PM PDT Tue Sep 19 2017


.SYNOPSIS...
Cooler weather this week with a chance of showers into Thursday.

&&

.DISCUSSION...

Models are in good agreement that a deep upper level trough and
associated cold front will move across interior NorCal. As a
result, expect precipitation chances later tonight through
Thursday. The best chance of precipitation will remain over the
mountains and over the northern Sacramento Valley. Forecast
guidance indicates that most locations will generally receive less
than 0.2 inches of precipitation, but some Sierra locations could
receive up to 0.35 inches.

The upper trough over the West Coast will usher in cooler air
aloft. Thus, snow levels could be lowering to around 6500 feet,
although they could be lower in heavier showers. Current forecast
indicates that there could be some light accumulations of snow
late Wednesday night into Thursday over the mountains.

In addition, the air mass will cool as the upper level trough
deepens and reinforces cooler temperatures. Therefore, daytime
highs are expected to remain 10 to 22 degrees below normal for
this time of the year. The coolest day of the week should be
Thursday, with Valley highs in the low to mid 70s.

By Friday, shower activity is expected to taper off as dry
northerly flow develops and the upper trough shifts eastward. As a
result, temperatures will trend upward slightly but will still
remain several degrees below normal.

&&
.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)
High pressure returns to northern California this weekend with
dry conditions and a warming trend to the afternoon temperatures.
High temperatures Saturday will remain below normal, but
temperatures Sunday into early next week will return to normal or
slightly above normal. Breezy north and east valley and ridgetop
winds can be expected for the weekend and into next week.

&&
.AVIATION...
VFR conditions for the valley terminals for the next
24 hours with light winds. Chances for light mountain rain
showers and increasing clouds tonight and Wednesday.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$


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