000
FXUS66 KSTO 260957
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
257 AM PDT Sun May 26 2019

.SYNOPSIS...
Widespread shower activity today with snow being forecast for the
higher Sierra elevations. Afternoon mountain showers or thunderstorms
continue through next week, with highs returning to near normal
by Tuesday.

&&

.DISCUSSION...
Water vapor satellite imagery shows a deep low dropping southward
into NorCal early this morning. Showers continue to spread across
the region as frontal boundary progresses southward, with some
lightning activity been detected. Observed precipitation amounts
so far are generally 0.10-0.90 inches; highest amounts located
over the NE portions of the forecast area. Wind gusts in the 15
to 30 mph range have been observed in the Valley.

This system will continue to bring widespread showers across the
region through late this morning. Then, decreasing shower
coverage is expected in the Valley with periods of mountain snow
continuing. There could be enough instability for thunderstorms to
develop late this morning into the evening hours mainly across
the southern portions of the Valley, and the eastern portions of
Shasta and Tehama counties.

This is a relatively cold system for this time of year, and will
likely lead to mountain travel impacts this holiday weekend
including travel delays, slippery roads, and possible chain
controls. Ensemble probabilities show the heaviest snow falling
early this morning, with 1-hr snowfall potentially exceeding 1".
Snow levels expected to drop as low as 5500-6500 feet early this
morning, with snow accumulations of 6 to 12 inches at pass levels;
locally higher for Sierra passes south of HWY 50. A Winter
Weather Advisory remains in effect for elevations above 6000 feet
across the Sierra-Cascade range through early Monday morning. If
traveling this weekend, make sure to check road conditions before
you go.

As the low exits the region on Monday, mountain showers will
become more isolated and scattered in nature. Elsewhere, dry
conditions are anticipated. In terms of temperatures, highs will
be as much as 10 to 20 degrees below normal today. Temperatures
will gradually warm up beginning Monday, with seasonal highs
expected by Tuesday, and the rest of the week.

&&

.EXTENDED DISCUSSION (Thursday THROUGH Sunday)

Long wave trough remains near 120W through the extended period
with mainly weak to moderate short waves tracking through. This
will keep an unsettled weather pattern. Threat of showers and
afternoon thunderstorms will be possible. Best chances will be
over the foothills and mountains and north of KSTS-KMYV line in
the Central Valley. High temperatures expected to be close to
average for late May.

&&

.AVIATION...

Areas MVFR/IFR conditions, with LIFR over mountains, as next
Pacific storm moves thru NorCal. Isolated thunderstorms possible.
Snow levels 050-060. Areas southerly surface wind gusts 20-30 kts
thru 18Z.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 AM PDT Monday for West Slope
Northern Sierra Nevada-Western Plumas County/Lassen Park.

&&

$$