Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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FXUS66 KHNX 192200

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
300 PM PDT Mon Mar 19 2018

.SYNOPSIS...Clouds will increase tonight with the approach
of a storm over the Eastern Pacific. This storm will bring
substantial precipitation to the district from late Tuesday
through Thursday along with very mild temperatures over the
higher elevations. Friday through Saturday will be dry and
unseasonably cool.


.DISCUSSION...Our last full day of Winter is turning out to
be a pleasant, sun-filled day.  It`s the proverbial "calm
before the storm", so to speak. The storm we`re referencing
is poised over the eastern Pacific this afternoon and it`s
going to pack a wet wallop when it arrives by midweek. With
its approach, the storm will spread thicker clouds over the
central California tonight. Clouds will continue to lower
and thicken across much of the CWA Tuesday, but until the
deeper moisture gets here toward sunset, precipitation out
of these clouds will be light...probably little more than
sprinkles in the valley and foothills and some snow flurries
over the highest elevations of the Sierra.

This storm will be in no hurry to move eastward during the
next 2-3 days. In fact, the models have now slowed its
eastward progression and don`t bring this system inland
over California until Thursday night. Up until then, a
broad southwesterly flow aloft in advance of this system
will carry a plentiful supply of rich subtropical moisture
into central and southern California. Upper level disturbances
embedded in this southwesterly flow will bring episodes of
precipitation into the CWA, and at times this precip will
fall heavily, especially in the orographically enhanced
regions such as the west slopes of the Sierra and the south
facing slopes of the Tehachapi mountains. Considering its
subtropical origins, this moisture will be accompanied by
very mild air during the next couple of days. During the height
of this storm Wednesday, snow levels may be up around 9,000
feet in the Sierra. So rain combined with melting snow will
cause rising water levels on area streams, excess runoff
and possible flooding. The greatest threat of flooding will
be in the foothills and higher elevations of the Sierra below
the snow level from Wednesday afternoon through Thursday
evening. During this time, some roads could become washed
out or impassable because of debris flows, rock slides and/or
mud slides. Above 8,000 feet where precip will fall primarily
as snow in the Sierra, accumulations of up to 4 feet are possible
by late Thursday. Elsewhere, here is the general breakdown of
how much rain we`re expecting by region from this storm through

Southern Sierra below 8,000 feet...3-6 inches
Sierra Foothills....2-4 inches
San Joaquin Valley...0.50-2 inches (heaviest on the east side)
Kern County mountains...1.5-3 inches
Kern County desert...0.25-0.75 inches

Colder air will begin to move southward into the CWA Thursday
evening, however by then, the heaviest precipitation will have
ended. Nonetheless, snow levels will probably lower to between
5,000 feet and 6,000 feet Thursday night and Friday. During
this time, snow showers at these elevations could leave a small
accumulation. Otherwise, a blustery, colder change in the
weather will take place across the central California interior
Thursday evening through Friday as the storm system finally
exits east of the Golden State. A generally dry west to northwest
flow aloft in the wake of this storm system will reside over
central California in the 5 to 7 day period.  At the start of
the weekend, a few showers could still linger over the Sierra
and the adjacent foothills from Fresno county northward. If so,
they won`t leave more than an additional tenth of an inch of
precipitation. Friday through the weekend will also average
much cooler than normal, however, next Monday should finally
become more seasonable.

In summary, although our midweek storm will bring generous
precipitation into much of central and southern California, it
will relieve but not end the drought. True, the rain is a great
thing, but too much of a good thing in a short period of time
can bring its share of hazardous impacts. Areas normally prone
to flooding may do so and many area streams will probably
experience water rises later this week. Folks need to be wary of
this and avoid driving on roads ponded with water. If you live
in a flood prone area or near a burn scar, be prepared to move
to a safer place should a threat of flooding occur. Hikers and
campers in the highest elevations of the Sierra should also be
prepared for potentially crippling snow and blowing snow by


VFR conditions will prevail accross the central California
interior during the next 24 hours.





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 for additional information
an/or to provide feedback.


.HNX Watches/Warnings/Advisories...
Flash Flood Watch from Wednesday afternoon through Thursday
evening CAZ093>097.

Winter Storm Watch from Tuesday evening through Thursday evening



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