Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
FXUS66 KHNX 221017
Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
217 AM PST Sun Jan 22 2017
.SYNOPSIS...A strong Pacific storm will bring strong winds,rain
and mountain snow to the region today and Monday. A drying trend
will begin on Tuesday with a continuation of dry weather for the
remainder of next week.
.DISCUSSION...A very strong Pacific storm is moving into the
region early this morning and lots of significant weather will
result. Regional radars shows widespread rain and snow over the
Central California interior and echoes really moving quickly as a
very fast flow is in place. For today the area will experience
heavy rain, heavy snow, strong to damaging winds and the threat of
flooding. I`ll break down each threat.
Wind: The combination of a very strong jet stream (150-180 mph)
pushing into Central California combined with deep low pressure
developing at the surface will result in potentially damaging
winds exceeding 80 mph in gusts over and near the Grapevine, the
San Emigdio Mountains near Frazier Park and Pine Mountain along
with canyons in this vicinity. Additionally strong winds will
affect parts of the San Joaquin Valley and the west side mountains
along and west of Interstate 5 where gusts exceeding 50 mph are
likely and some higher, damaging gusts could occur if stronger
winds translate to the surface. Winds will begin to subside this
afternoon and evening. High winds near the Grapevine are covered
in the Winter Storm Warning product while the San Joaquin Valley
winds are noted in the Wind Advisory.
Rain and the potential for flooding: Heavy rain will fall below
the snow line, which will start out around 4500 feet this morning
and rise to over 8000 feet during the day as much warmer air moves
into especially southern parts of the area. With heavy rain on
saturated soils, flash flooding is certainly possible and a Flash
Flood Watch is in place. With very strong wind flow over the
mountains west of the San Joaquin Valley, a pronounced rain shadow
is likely over the west side where amounts of just a few
hundredths of an inch are expected today. Meanwhile, the opposite
is likely over the east side of the SJV where heavier rains
approaching an inch are possible.
Snow: As mentioned in the section above, snow levels will rise
today rather drastically however by later tonight and Monday,
colder air will arrive and drive snow levels down to below 4000
feet. Expected snow amounts are noted in the Winter Storm Warning
products. In general, 2-4 more feet of snow is likely at higher
elevations of the Sierra with lesser amounts below.
So, how does this storm come to an end? Forecast models keep lots
of instability (colder air aloft) moving into the forecast area on
Monday and scattered thunderstorms will break out over most of
the area. By Monday night and Tuesday, the very deep and strong
area of low pressure currently located off the Oregon and
Washington coast will move down the coast later Monday and Tuesday
and then move east of the area by later Tuesday. This will bring
precipitation to an end. From Wednesday through the upcoming
weekend things look dry as high pressure ridging is projected to
build over the West.
In the San Joaquin Valley, areas of MVFR in rain and low clouds over
region. Wind gusts over 35KT possible thru 06Z Monday. In the
southern Sierra Nevada and adjacent foothills, mountain obscuring
IFR in low clouds and precipitation prevailing with areas of LIFR.
Strong southwest winds in excess of 35KT over the ridge tops. In the
Tehachapi Mountains and valley facing slopes, areas of mountain
obscuring IFR and local LIFR in low clouds and precipitation. Strong
gusty southerly winds in excess of 35KT over the ridge tops. Winds
over 50KT possible near the Grapevine. Otherwise, VFR conditions
will prevail during the next 24 hours.
.AIR QUALITY ISSUES...
The level of certainty for days 1 and 2 is high.
The level of certainty for days 3 through 7 is high.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.php for additional information
an/or to provide feedback.
Winter Storm Warning until 10 AM PST Monday CAZ096-097.
Flash Flood Watch through this evening CAZ093>097.
Winter Storm Warning until 10 AM PST Monday CAZ095.
Wind Advisory until 10 PM PST this evening CAZ089>093.