Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
FXUS66 KHNX 192230
Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
230 PM PST Thu Jan 19 2017
A series of Pacific storm systems will continue to move inland
across the state through Monday, bringing periods of rain and
mountain snow along with gusty winds to the region.
Unsettled weather continues across the Central California Interior
as yet another in a series of storms moves through the region.
While lingering convective showers will continue this afternoon,
the next major storm will enter Northern California overnight into
early Friday morning. Model and observed upper air analysis is
showing a good potential for thunderstorms today moderate
instability invades the Central California Interior after 12 Noon.
Regional doppler radar is already indicating weak to moderate
showers crossing the San Joaquin Valley and pushing into the
foothills. Storm Prediction Center has the Central California
Interior in a risk of general thunderstorm activity. Therefore,
while moderate thunderstorms could be generated, will expect weak
thunderstorm activity based on model and observed analysis.
Furthermore, based on the time of each Pacific storm, fog may be
limited due to the unsettled conditions expected for the next few
As for the previous storm, Central California did manage to
receive between a third to three quarters of an inch of rain in
the lower elevations while giving the Sierra almost 2 feet of new
snow. Upper air observations from Vandenberg and Oakland showing
freezing levels above 5000 feet with the potential for snow down
to near 4000 feet. Will expect the current cold front to exit the
region this evening as warm frontal precipitation starts
overnight. Due to the timing of the next frontal system, snow
levels may rise overnight and keep the heavier accumulation above
4000 feet. As for the Grapevine, snow levels will remain well
above 4000 feet and not greatly impact Interstate-5.
While precipitation may start during the morning on Friday, the
bulk of heavy precipitation from the next storm is currently
progged to occur during the mid-day to afternoon hours. Current
model progs have the cold frontal passage during the latter part
of the day, which may enhance convective potential for Friday.
250Mb wind analysis has the jet core dropping toward Southern
California on Friday, which may provide the area with good left
front quad dynamic lift. Therefore, will go ahead and continue the
threat of thunderstorms again on Friday. Furthermore, the passage
of the cold front will allow for an increase in surface winds
across the San Joaquin Valley. Issued a wind advisory for areas
near Merced and Interstate-5 as surface pressure gradients tighten
Another in a series of storms will move onto the west coast on
Sunday with a possible better tap of moisture from the
subtropics. While the next storm before the weekend will have some
moisture, the weekend storm will have an even better moisture tap
and dynamic lift potential. Model upper air analysis is showing
good consensus of having the upper low dig down to near the
Northern California Coastal border with good difluent flow over
Central California on Sunday. In addition, models show even colder
air filtering into the region this weekend to lower snow levels.
While a winter weather advisory exist for the Kern County
Mountains, Sunday may be the time period while snow may affect the
Grapevine area and Tejon Pass. Monday will see a continuation of
unsettled conditions as cyclonic flow remains over the west coast.
The area of Neg. Vort. Advection may not reside over the west
coast until Wednesday. Confidence is increasing on introducing a
dry period starting on Wednesday of next week.
Isolated thunderstorms can be expected over mainly the San Joaquin
Valley and adjacent foothills through 03z Friday with a recurrence
in the same areas between 19z Friday and 03z Saturday. Areas of
MVFR ceilings with local IFR in heavier precipitation can be
expected in the mountains through 06z Friday. Widespread IFR
conditions with mountain obscurations will develop in the Sierra by
12z Friday and continue through 00z Saturday. Additionally, local
wind gusts of 35 knots or greater are possible in the northern San
Joaquin Valley and the west side of the San Joaquin Valley
between 11z Friday and 19z Friday. VFR conditions can be expected
elsewhere across the central California interior during the next
.AIR QUALITY ISSUES...
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
an/or to provide feedback.
Winter Storm Warning from 4 AM Friday to 10 AM PST Saturday
for the Sierra Nevada from Yosemite to Kings Canyon and the
Tulare County Mountains /CAZ096-097/.
Winter Weather Advisory from 7 AM Friday to 4 AM PST Saturday
Above 5000 feet for the Kern County Mountains /CAZ095/.
Wind Advisory from 3 AM to noon PST Friday for the Central
and Southern San Joaquin Valley /CAZ089>091/.