Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 201236
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
436 AM PST Tue Feb 20 2018

.SYNOPSIS...
Below normal temperatures and periods of showers mainly over the
mountains will persist through the week. Stronger system may move
across the area early next week.

&&

.DISCUSSION...

With a cold airmass in place, current temperatures are chilly with
most Valley locations ranging from the mid 20s to mid 30s.
However, winds have prevented overnight temperatures to drop
significantly. Dry conditions are anticipated on Tuesday with
highs in the 50s across the Valley. While not as cold as previous
nights due to increasing cloud cover, Wednesday morning lows could
be near or below freezing throughout much of the Central Valley
resulting in areas of frost. Therefore, a Hard Freeze Warning
continues for areas below 2000 feet through Wednesday morning.

Unseasonably low heights will persist along the West Coast with
a series of short waves pivoting through the main feature
Wednesday into the weekend. These systems are expected to bring
periods of showers generally over the mountains with a stronger
wave moving in Thursday into Friday. Models indicate some
precipitation activity making its way across the Valley late this
week, but any precipitation amounts are expected to be less than
0.10 inches.

QPF amounts will be limited with these systems, but a few inches
of snow will be possible at pass levels. This may be enough to cause
some slick roads, but not expecting major impacts. Snow levels
down to 1000 feet could give a dusting down to the foothills and
lower elevations of Shasta county. In addition to shower activity,
temperatures will remain below normal through the period as cold
air continues to filter in.

&&

.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)

A weak shortwave will clip the northern portions of the state
Saturday into Sunday, and could bring a few snow showers to the
northern mountains and Sierra Nevada. Most of the region will
likely remain dry over the weekend however under dry northerly
flow.

A subtle but perhaps meaningful pattern shift toward wetter
weather is looking a bit more likely for next week. Shortwave
troughs will continue to drop out of the north, but may remain a
bit farther offshore as they do, allowing them to tap into more
abundant moisture. These systems will still originate from Alaska
/ western Canada, so the colder airmass should persist. The GFS
and ECMWF have come into better agreement on this solution, which
gives us a degree of confidence in this pattern shift. The net
result: potential for wetter (but not abundantly wet) weather
along with moderate to heavy mountain snow and low snow levels.

Dang

&&

.AVIATION...

VFR conditions with mostly light winds are expected the next 24
hours.

Dang

&&

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

$$


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