Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
FXUS66 KHNX 202132
Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
232 PM PDT Mon Mar 20 2017
.SYNOPSIS...A strong cold front will bring precipitation to the
area tonight and Tuesday as it moves through the region. Cooler
than normal temperatures and unsettled conditions will then
prevail through the middle of the week in a cooler and unstable
airmass. Another storm will move through the area on Friday and
Saturday bringing additional precipitation.
.DISCUSSION...The warm and dry airmass that has been in place
across our area for the past several days is about to be
displaced as a strong Pacific low pressure system currently
situated off the Norcal coast near 40N/141W approaches Norcal.
Ahead of this system high clouds continue to stream across our
area in a southwest flow aloft over Central CA. One wave which
moved through the area in the southwest flow produced some locally
gusty winds along the west side of the San Joaquin Valley earlier
this morning which have since diminished. Current observations
are indicating that temperatures are running fairly close to yday
at this time.
The 12Z WRF and the short term models are in good agreement with
spreading the deeper moisture southward through our area tonight
as the low approaches the Norcal coast. Precipitation will move
into the Merced and Mariposa Counties later this afternoon and
reach the Fresno area by late evening spreading south of Fresno
County overnight and into the Tehachapi Mountains and Kern County
Deserts Tuesday morning. With a mild airmass remaining in place
ahead of the incoming system snow levels will be high tonight and
Tuesday (8500 to 9000 feet) until the main cold front pushes
through on Tuesday afternoon. In addition, thunderstorms will be
possible across our CWFA on Tuesday afternoon as our area will be
in the LFQ of a 100 KT 250 MB jet maxima on Tuesday afternoon with
the WRF indicating LI/s of -7 and -4 DEG C and CAPES between 800
and 1200 J/KG over much of the the San Joaquin Valley. The one
factor that could inhibit thunderstorm development on Tuesday is
if there is too much cloud cover in the colder post-frontal
By Wednesday there should be enough clearing in the colder and
unstable post-frontal airmass for thunderstorm development on
Wednesday afternoon. Otherwise it will be a showery day with
temperatures much cooler than we have recently been accustomed to
with daytime highs expected to be near to slightly below normal
and snow levels lowering to 6000 to 7000 feet. Precipitation
totals across our area will vary depending on which locations are
impacted by heavier showers and thunderstorms. Most of the valley
will pick up between a quarter to three quarters of an inch of
rain while the Southern Sierra Nevada will receive between 1 and 2
inches of liquid precipitation.
The upper low is progged to move east of our area on Wednesday
Night and a shortwave ridge will temporarily reside over Central
CA on Thursday bringing a brief respite from the active weather to
our area. A few light showers will still be possible in The Kern
County Mountains south of Tehachapi and near the Sierra Crest as
the result of lingering upslope conditions. Otherwise Thursday
will be partly cloudy with seasonable temperatures.
The medium range models and their ensemble means are indicating a
potentially very wet system approaching the region on Friday which
will bring more precipitation to our area on Friday Night and
Saturday. This system is progged to be stronger than the system
moving through tonight and Tuesday and has the potential to
produce heavy precipitation. This system will move east of our
area on Satruday Night. Unsettled conditions will then prevail
into the following week as yet another system might clip our area
Sunday Night and Monday.
.AVIATION...Light rain will impact the terminals late tonight
into Tuesday morning. Otherwise...VFR cigs and vis will prevail
through at least the next 24 hours.
.AIR QUALITY ISSUES...None.
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.