Flash Flood Warning 1, NWS Hanford, CA

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
1230 PM PST Wed Jan 16 2019

.SYNOPSIS...A third and final storm system will enter Central
California today. Periods of heavy rain, mountain snow, strong
winds will begin this afternoon and will last through Thursday.
Fog will be possible in the San Joaquin Valley starting Friday
morning, and is possible Saturday and Sunday morning. A weak
disturbance will impact the area Sunday, followed by an extended
period of dry weather.

&&

.DISCUSSION...
This week has been full of unsettled weather, and the storm system
that comes in later today will be the apex event of the week
bringing multiple weather-related impacts. Currently,
precipitation is north of us in the Bay Area and Sacramento
Valley, but it will edge southward throughout the day. Into the
afternoon, precipitation associated with this storm
system/atmospheric river will first impact the northern portion of
the CWA. The likelihood of intense rainfall rates in the Southern
Sierra Nevada below 7,000 and foothills will increase as we
progress later into the night. This will increase the risk of
flash flooding in areas that have excess runoff, and a risk of
Debris Flows and Mudslides over burn scars, especially the
Ferguson and Pier Burn Scars, will need to be monitored throughout
the night. The time frame of the most intense rainfall looks to
be between 2 AM PST through 6 AM PST Thursday morning associated
with the frontal passage. Precipitation will continue into
Thursday, so a clap of thunder or two will possible due to better
lapse rates aloft. Due to the possibility of heavy rain starting
this afternoon, and additional rain tomorrow, a Flash Flood Watch
remains in effect for Mariposa, Madera, and Fresno County
Foothills, Sierra Nevada from Yosemite to Kings Canyon, Tulare
County Foothills, and Tulare County Mountains through 10 PM PST
Thursday. Light precipitation will continue until early Friday
morning across the district. Rainfall totals in these areas will
be in the 2-4 inch range, with localized areas of 5-6" possible.
Rain in the valley may cause some nuisance flooding in urban
areas. Totals will be 1 to 1.5 inches in the northern portion of
the valley, and .5-1 inches in the southern portion of the valley.

In terms of winter weather, we currently have a Winter Storm
Warning that will be valid starting 4 PM today through 10 PM
Thursday for the Sierra Nevada from Yosemite to Kings Canyon and
Tulare County Mountains above 7,000 feet. Snow levels will be in
the 7,000 foot range across the Sierra Nevada this afternoon and
evening, and will slowly rise to just over 8,000 feet by tomorrow.
Heavy snow will begin to fall as the atmospheric river enters the
region, and creating nearly white-out conditions. Strong, to very
strong wind gusts of 65-85 mph will be possible for exposed
ridgetops. This will create treacherous conditions for anybody
traveling in the Southern Sierra Nevada during the timeframe of
the Winter Storm Warning. Anybody who exposes themselves to these
conditions will be endangering their life, and rescue missions may
be nearly impossible. Snow fall totals will be 1-3 feet, with
localized areas of 4-5 feet of snow possible by Friday morning
from this system alone.

We have two Wind Advisories that will be valid later today. The
first Wind Advisory will be valid 1 PM PST today through 1 AM
Thursday for the west central portion of the San Joaquin Valley
and foothills including and north of Fresno County. Southeast wind
gusts up to 45 mph are possible in these areas. Areas that have
wet soil could see some trees blown down when gusts get over 40
mph. The second Wind Advisory is for the Southwestern Valley and
Mountainous areas in Kern County west of Highway 58, as well as
the Grapevine area where a strong off shore pressure gradient will
set up through the night. This advisory is in effect starting 6
PM tonight through 4 AM Thursday morning... southeast 20 to 30 mph
with gusts up to 45 mph possible. Local gusts up to 55 mph
possible in the Grapevine area, as well as Cummings Valley.

Starting Friday morning, fog formation may be possible in the San
Joaquin Valley as shortwave ridging moves over the area.
Conditions will be conducive to fog formation due to the decrease
in winds and added boundary layer moisture from the recent
rainfall. We have added fog in the forecast for Friday morning
and Saturday morning. Fog may also be possible Sunday morning, but
have held off on putting it into the forecast as there is a fair
amount of uncertainty in forecasting fog this far out. On Sunday
and into early Monday morning, a trough of low pressure aloft
will bring impacts mainly to the north of our forecast area, but
will still introduce a chance of precipitation into the area
starting Sunday morning and lasting through Sunday night.
Rainfall/snowfall rates look to be fairly tame with this system.

In the long term, courser resolution models are showing
a significant Eastern Pacific ridge forming on late
Monday/Tuesday. Models are showing the ridge of high pressure
aloft staying in place/amplifying through the rest of the
forecast period. This will mean daily occurrences of morning Tule
Fog are possible in the valley as winds will likely be light and
variable along with the antecedent wet soil/appreciable boundary
layer moisture from the barrage of precipitation we get this week.
Dry weather will also occur next week as ridging persists, and
will continue into the foreseeable future as CPC progs have
Central California at well-below average chance for precip in the
6-10 day range.

&&

.AVIATION...
Areas of mountain obscuration across the Southern Sierra Nevada and
Tehachapi mountains becoming widespread after 00Z Thu due to
precipitation and low clouds. Windy conditions over much of central
CA with strong wind gust 35+ kts expected over higher mountain
terrain. Thunderstorms will be possible across the San Joaquin
Valley after 12Z Thur. Otherwise areas of MVFR conditions with local
IFR conditions through 00Z Fri due to rain and mist.

&&

.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.html for additional information
an/or to provide feedback.

&&

.HNX Watches/Warnings/Advisories...
Flash Flood Watch from 4 PM PST this afternoon through Thursday
evening CAZ093-094-096-097.

Winter Storm Warning from 4 PM this afternoon to 10 PM PST
Thursday ABOVE 7000 FEET FOR THE CAZ096-097.

Wind Advisory from 6 PM this evening to 4 AM PST Thursday
CAZ091-095.

Wind Advisory until 1 AM PST Thursday CAZ089-090-093.

&&

public...Bollenbacher
avn/fw...MV
synopsis...Bollenbacher

weather.gov/hanford