Heavy Snow in California, March 9 to 11, 2021

Area Forecast Discussion
National Weather Service Hanford CA
121 PM PST Tue Mar 9 2021

.SYNOPSIS...A cold storm system will bring scattered showers
to the district through Thursday with snow above 2,500 feet.
Heavy snow accumulations are likely above 5.000 feet by Thursday
evening. Temperatures will average well below normal through
Thursday. Dry weather will return later this week and continue
into the weekend with temperatures warming to near normal by
Saturday.

&&

.DISCUSSION...A cold storm system that originated in the Gulf of
Alaska is going to bring generous snow to the mountains of central
California during the next 36 hours with beneficial rain in the
lower elevations. It's been more than five weeks since a storm of
this magnitude has done so, and it couldn't be more welcome!
Unfortunately, the precipitation this storm brings won't be nearly
enough to catch us up on this exceptionally dry Winter season.
There are indications now that we could get another opportunity
for wet weather later this weekend into early next week, but
not all of the models agree on that which we'll address later in
this discussion.

As of this writing, our next storm system is situated off the
Pacific Northwest coast. A strong southwesterly flow aloft to the
south of this storm is centered right over our CWA this afternoon.
This 300 MB jet will support gusty winds through and below the
Kern county mountain passes into the early part of tonight. The
upper level jet is currently producing orographic precipitation
over the Sierra. Meanwhile, little in the way of convection is
currently happening over the remainder of our CWA, although isolated
showers are not out of the question in the San Joaquin Valley and
foothills between now and sunset.

The models are in very good agreement and forecast this upper
level low to drift southeastward during the next 36 hours. As
the cold core low gets closer, shower activity will likely
increase over much of the CWA tonight and Wednesday. Additionally,
the upper level jet will gravitate south of our CWA by Wednesday.
This will put us in the colder and more unstable side of the
upper level jet by Wednesday afternoon and evening and increase
the probability of isolated thunderstorms, particularly over the
western third of the San Joaquin Valley. Small hail, gusty winds
and heavy downpours may accompany any of these thunderstorms
Wednesday afternoon. In the meantime, this cold core low will
produce an abundance of snow in the mountains. Snow levels will
lower to about 3500 feet tonight, but could drop as low as 2500
feet in heavier showers Wednesday afternoon and evening. This
will of course impact travel through the mountain passes, so
motorists should prepare for potentially hazardous winter driving
conditions in these areas and be prepared for long delays and
possible road closures due to snow and ice.

The bulk of this storm's precipitation will likely fall between
tonight and Thursday morning. Afterward, this slow moving storm
will drift south of Kern County, but while it sits over southern
California late Thursday through Thursday night, it could still
bring additional showers to the mountains and desert along with
residual winter hazards above 3500 feet. If you haven't guessed
already, high temperatures during the next couple of days will
average well below normal. Most locations in the San Joaquin
Valley and the Kern County desert will be no higher than the
50s Wednesday and Thursday.

This storm is forecast to exit into Arizona by the end of this
week. However, there is concern that wraparound moisture from it
could still produce a few showers over the mountains and desert
Friday. Otherwise, a brisk north to northeast flow aloft in the
wake of this storm system will bring a drier air mass into the
district Friday evening and night. An upper level ridge of high
pressure will build into the Golden State this weekend. High
temperatures should bounce back to near normal Saturday and
Sunday while this ridge is over us.

The models are very undecided on the track of the next storm
system late this weekend into early next week. If the GFS is
correct, we'll get another round of wet weather late Sunday
through Monday. The ECM, on the other hand, forecasts this storm
system to track well to our north, which would leave the central
California interior high and dry, so our confidence is medium
at best until the models come into better agreement in the
extended periods.

&&

.AVIATION...MVFR conditions will prevail over the foothills
and mountains during the next 24 hours with areas of IFR/LIFR in
precipitation. VFR conditions can be expected elsewhere although
Local MVFR ceilings are possible in heavier showers and isolated
thunderstorms in the San Joaquin Valley through 00z Thursday.
Additionally, wind gusts in excess of 35 knots are likely through
and below the Kern county mountain passes until 06z Wednesday.

&&

AIR QUALITY ISSUES...
None.

CERTAINTY...

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

&&

.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...
Winter Storm Warning from 4 PM this afternoon to 10 PM PST
Wednesday for CAZ190>195.

Wind Advisory until 10 PM PST this evening for CAZ195>199.

Winter Storm Warning from 10 PM this evening to 4 PM PST
Thursday for CAZ196-197.

&&

synopsis...Durfee
public/aviation/fw...Durfee
PIO/IDSS...BS

weather.gov/hanford