Flash Flood Warning 6, NWS Hanford, CA

Area Forecast Discussion
National Weather Service Hanford CA
117 PM PDT Sun Apr 5 2020

.SYNOPSIS...
A strong late season storm system will bring heavy rain and
snowfall to the region through Monday afternoon. Additional
precipitation is possible into the southern half of the district
late Tuesday into Wednesday. Conditions will dry out and warm up
by the end of the week.

&&

.DISCUSSION...
After a nice stretch of days, we are tracking a major storm
system that is dropping south from the Gulf of Alaska. It is a
very cold storm system that is remaining over the oceans and is
tapping some decent moisture with it. Regional radar and satellite
loops are indicating two main bands of moderate to heavy
rainfall. The first band is making its way through Merced and
Fresno with only light amounts. The main cold front is still
north of Merced and will be making its way south this afternoon
and evening.

We are already seeing gusty winds along the west side of the SJV
and into the coastal hills. We issued a wind advisory this morning
and as the main cold front gets closer, wind will increase across
the SJV and over the Sierra ridges. Rainfall rates up to one half
of an inch per hour are possible over the Briceburg/Ferguson burn
scar and flooding is possible. Rainfall amounts are fairly
impressive across the SJV as well. We are a bit concerned that
they might be a bit overdone, but when the front pushes through
overnight tonight is when we expect the heaviest rain. the
orientation of the front is also important as the low center
slides down the coast the front will become more of a north and
south orientation and we could see training storms and heavy rain
going over the same area. This could lead to some minor flooding
over poor drainage areas in the SJV.

The current snow level as of noon was around 5500 feet and is
expected to stay there most of the event. It will drop to around
4000 feet in the Sierra behind the front tomorrow morning. Snow
fall rates will be as high as two to three inches per hour with
the frontal band over night in the Sierra. Couldn't rule out some
rumbles of thunder in the heaviest snow bands. The NAM and hires
NMM are trying to shadow the SJV as the front pushes through.
However we are still expecting decent rainfall over the region.
this is a different soln from the EC and GFS deterministic runs
from 12z which are both wetter for the SJV. This could be a
resolution issue. Snow levels are expected to be around 6000 feet
for the Kern county mountain areas and they could see significant
snow in the Cuddy Valley area and around Pine Mountain Club.

The upper level low center will be veryslow to move south on
Monday as it will remain nearly stationary off the CENCAL coast.
Continued impulses will keep the chances of rain and high
elevation snow across the CENCAL interior. A continued possibility
of thunderstorms on Monday mainly along the west side of the SJV.
Periods of moderate to heavy rain is still expected on Monday
afternoon and evening. The low center is forecast to slide south
towards Pt. Conception by Tuesday with the focus turning to kern
county and the possible impacts there. Strong southerly flow will
potentially create downsloping wind issues through the Grapevine
pass as well as moderate rain and high elevation snow Tuesday
night as wrap around moisture becomes more intense.

As the low center continues to move south and east on Wednesday,
we are expecting drying conditions from the north and spreading
south Wednesday night. EPAC ridge of high pressure will build on
behind the exiting low center. Warming trend with dry conditions
are expected late Thursday and continue through next weekend.

&&

.AVIATION...
For the southern San Joaquin valley and Sierra foothills: MVFR
conditions with local IFR ceilings and visibilities likely.
Additionally, moderate to locally heavy rain showers and isolated
thunderstorms will intensify throughout the day, eventually ending
by Monday afternoon.

Over the Sierra Nevada and Kern County mountains: expect IFR due
to precipitation and mountain obscurations through at least
Monday evening.

&&

.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 high.

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

&&

.HNX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 5 PM PDT Monday for CAZ192>194.

Wind Advisory until 8 PM PDT this evening for CAZ179-180-182.

Winter Storm Warning from 5 PM this afternoon to 11 PM PDT
Monday for CAZ195>197.

&&

public......JDB
aviation....JDB
pio/idss....AB

weather.gov/hanford

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