Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
FXUS66 KHNX 222238
Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
238 PM PST Wed Feb 22 2017
Isolated showers can be expected in the Sierra foothills and snow
showers in the Sierra Nevada and Kern County Mountains this
afternoon. Dry weather will prevail Thursday and Friday, with the
next system aimed to impact the region later this weekend.
Convective showers continue this afternoon across parts of central
California as an upper level trough moves onshore. Radar imagery
at 2 pm PST shows some returns in the Sierra foothills -- in
fact, Sequoia National Park Headquarters reported small hail
associated with a convective shower around 1230 pm PST.
Temperatures are running 5-15 degrees cooler than they were at
this point yesterday afternoon across the region.
The primary short-term concern is the potential for hazardous
travel in Kern County Mountains as northwest/upslope flow favor
precipitation development through the overnight hours. As cooler
air continues to infiltrate the area, we`ll see snow levels fall
from 5,000 ft today to perhaps as low as 3,000 ft overnight and
into tomorrow morning. Major passes -- including Tejon/Grapevine and
Tehachapi -- will have an increased chance of seeing snow after
sunset as the snow levels fall. Motorists with plans to travel
through the mountains this afternoon and tonight should plan
accordingly for possible slow travel and slick conditions, and are
advised to check CalTrans for the latest road conditions. A
Winter Weather Advisory continues for the Kern County Mountains
until 11 am PST Thursday.
Another concern in the short-term are the gusty winds, especially
in the Kern County Mountains and Desert. The surface pressure
gradient between San Francisco and Las Vegas at 2 pm PST was 15.2
mb -- a more than sufficient difference to create Wind Advisory-
level winds to parts of Kern County. West winds of 20-30 mph with
gusts to 50 mph are expected to continue through early tomorrow
morning. The Wind Advisory continues for the desert until 1 am PST
Northwest flow will persist over the region on Thursday with
temperatures expected to remain 5-10 degrees below normal for
this time of year. The next challenge in the forecast will be on
Friday morning as clear conditions and calm winds allow for
temperatures to drop to potentially sensitive levels for
agriculture. The big question is how cold temperatures will
actually get. With recent weeks` abundant rainfall allowing
agricultural fields to remain wet and saturated, temperatures may
stay a couple of degrees warmer than models suggest. At this point
we have introduced patchy fog and frost in areas of the San
Joaquin Valley by daybreak Friday. Confidence remains low at this
point for specific low temperature values, so we urge folks to
monitor the forecast for the latest information.
Models are advertising a cooler storm system to impact the region
as we head into the weekend. Both GFS and ECMWF models suggest
precipitation arriving to the Sierra by late Saturday night,
spreading southward into Sunday. With the cooler air, snow levels
are expected to be lower than prior weeks` storm systems. By
Tuesday and Wednesday next week models suggest a ridge to develop
over the West Coast with dry conditions and temperatures near or
slightly below normal for this time of year.
.AVIATION...MVFR conditions along west facing slopes of the Sierra
and west and north facing slopes of the Tehachapis through 00z
Friday, with local IFR and mountain obscurations in precipitation
over the higher elevations through 06z Thursday. Winds will gust
over 40 KT across the mountain and desert areas of Kern County
through 09z Thursday. VFR conditions will otherwise prevail across
the central California interior during the next 24 hours.
.AIR QUALITY ISSUES...
The level of certainty for days 1 and 2 is medium.
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 Weather Advisory until 11 AM PST Thursday CAZ095.
Wind Advisory until 1 AM PST Thursday CAZ098-099.