Flash Flood and Flooding in California, February 17 to 20, 2017

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
308 AM PST Fri Feb 17 2017

.SYNOPSIS...Unsettled weather will continue across central
California through at least the middle of next week.

&&

.DISCUSSION...An upper low...currently about 800 miles west of the
San Francisco Bay...continues to move east southeast toward the
central and southern California coastline this morning. This low
is tapping into abundant atmospheric moisture that extends well
west of the Hawaiian Islands. In fact...the blended total
precip water is showing a bullseye of 2.2 inches off the San Luis
Obispo and Santa Barbara coastline. Light to occasionally moderate
rain impacted Kern county all of yesterday...but is now spreading
north into Fresno county and far western Merced county. This
activity is forecast to continue through the day...with rain rates
increasing into the late morning hours.

All of central California will see precipitation much of the day
today...with the greatest amounts over the Kern county
mountains...especially near the Grapevine. The Sierra Nevada and
surrounding foothills will also receive significant
precipitation...with a continued concern of flash flooding with
already saturated soils.

Expect between a half inch and an inch of new rain over the
valley...between an inch and two inches in the foothills...and up
to 2.5 inches in the mountain below 7000 feet. The one exception
will be the Kern county mountains...where a few areas...especially
near the Grapevine...could pick up upwards of 4 inches of new rain
in a 24 hour period ending early Saturday morning.

Snow levels will generally hover around 7000 feet through early
Saturday morning...with between 12 and 20 inches of snow possible
over the Sierra Nevada above 7000 feet. A few areas...especially
across Sequoia and Kings Canyon National Park could see snow
amounts in excess of 2 feet in the next 24 hours.

Very strong winds will be present as the upper low shifts closer
to the central coast and the surface pressure gradients
strengthen. The HRRR shows southerly winds rapidly increasing
around 15z...with the strongest winds generally between 17z and
22z. The strongest winds will be observed over the Kern county
mountains...more specifically from Pine Mountain Club east to
Lebec on the Grapevine. The HRRR shows wind gusts between 70 and
80 kts...or up to 92 mph between around 16z and 19z. These winds
will be extremely damaging...with widespread downed trees,
powerlines, prolonged power outages, and extremely dangerous
driving conditions. We cannot stress enough that these winds will
be very damaging.

Strong winds are also forecast for much of central California
during this same time frame...with wind gusts to over 40 mph
across the northern and western portion of the San Joaquin Valley.
The foothills in Mariposa and Madera counties will also see some
of the strongest winds...with gusts near 50 mph.

One last item with this storm...thunderstorms will be possible
this afternoon into the early evening hours...especially along
the west side of the San Joaquin Valley.

The upper low will move onshore near the San Francisco Bay area
late tonight into early Saturday morning...with scattered showers
across the area Saturday into Sunday.

Another upper low will approach the Pacific Northwest coastline
Sunday night into Monday morning...bringing another round of
widespread precipitation to central California Monday into
Tuesday morning. Unsettled weather remains in the area through at
least next Friday. There will be breaks in the weather during this
time frame...we will continue to nail down timing over the weekend
into early next week.

Again the main concern of the forecast will be over the next 24
hours...with extremely strong winds this morning into the
afternoon hours and flash flooding especially over the mountains
below 7000 feet. Please continue to maintain weather awareness
today and stay safe.

&&

.AVIATION....IFR conditions will prevail over the mountains due
to precipitation, low ceilings and mountain obscurations. Local
MVFR conditions can be expected in the Sierra foothills in
episodes of heavy rain during the next 24 hours. Additionally,
strong winds gusting over 35 knots will occur in the northern San
Joaquin Valley and through and below the mountain passes of Kern
County as well as the south end and west side of the San Joaquin
Valley through 03z Saturday. VFR conditions can be expected
elsewhere over the central California interior during the next 24
hours.

&&

.AIR QUALITY ISSUES...
None.

&&

.CERTAINTY...

The level of certainty for days 1 and 2 is high.
The level of certainty for days 3 through 7 is medium.

Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.php for additional information
and/or to provide feedback.

&&

.HNX Watches/Warnings/Advisories...
Flash Flood Watch from 7 AM PST this morning through late
tonight CAZ093>099.

Wind Advisory from 7 AM this morning to 7 PM PST this evening
CAZ089>092.

High Wind Warning from 7 AM this morning to 7 PM PST this
evening CAZ095.

Winter Storm Warning from 7 AM this morning to 4 AM PST Saturday
ABOVE 7000 FEET FOR THE CAZ096-097.

&&

public...Riley
avn/fw...Durfee
synopsis...Riley

weather.gov/hanford