Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
FXUS66 KHNX 281050
Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
350 AM PDT WED SEP 28 2016
.SYNOPSIS...A disturbance moving over southern California will
continue to spread tropical moisture over the mountains and desert
with showers and thunderstorms possible today. A gradual cooling
trend will bring temperatures down to near normal by Friday then
more significant cooling for the weekend with highs falling to
around 10 degrees below normal.
.DISCUSSION...Upper low over northern Baja is continuing to move
north and spread increasing mid and high level moisture into the
southern portion of our cwfa from the east. IR imagery indicating
a significant increase in mid level clouds over the Kern County
mountains and deserts overnight. Radar composites are not showing
much in the way of precipitation at this time. However, deeper
moisture and increased instability and CAPE are expected over the
mountains and Kern County Deserts by this afternoon as the low
moves into Socal and wraps around tropcial moisture pulled up from
Tropcial Storm Roslyn (currently centered near 20N/116W and moving
slowly northward) which will provide for a chance of showers and a
slight chance of thunderstorms over The Kern County mountains and
deserts and the southern Sierra Nevada from Fresno County
southward. The northward progression of the low will also provide
for synoptic cooling over our area today and afternoon
temperatures will be a few degrees low today than the past tow
days as a result although temperatures will still be well above
06Z WRF is indicating the low will lift into the Great Basin
tonight, but enough lingering moisture and instability will remain
near the crest of the southern Sierra Nevada for a slight chance
of afternoon thunderstorms on Thursday. A deep upper low is
progged to approach the PAC NW coast on Thursday and Friday which
will continue the ongoing cooling trend as heights and thicknesses
fall. By Friday as pronounced southwest flow will push any
lingering tropcial moisture well to the east of our area.
The medium range models are in good agreement with pushing the
upper low inland across the PAC NW on Saturday. A cold front
ahead of the system will drop southward through central CA Friday
Night bringing a period of increased winds followed by much cooler
temperatures across our area this weekend. While afternoon highs
in the San Joaquin Valley had been near the century mark the
previous two days; by Saturday afternoon highs are only expected
to reach the mid to upper 70s in the San Joaquin Valley. The
models are reaching more of a common ground with another low
which will drop down the back side of the Saturday trough and
bring precipitation to Norcal. While the deeper moisture is
expected to remain just to the north of our area, the mod trend
has been showing a deeper system so will mention a slight chance
of showers for Yosemite Park on Sunday and Monday at this time.
The main impact this system will have for our area; however, will
be breezy to windy conditions from Sunday Night through Monday
Night across the Kern County mountains and deserts.
This secondary system is then progged to move into the Great
Basin Monday Night leaving our area under a cool northwest flow
through the middle of next week as an upper ridge amplifies off
the coast near 135W. A drying trend will take place with
temperatures remaining below normal through the middle of next
week as a result.
.AVIATION...Scattered thunderstorms are expected to develop over
the sierra and Kern county mountains and desert during in the
afternoon from 20z to 04z. Otherwise VFR conditions will prevail
over the Central CA interior during the next 24 hours.
.AIR QUALITY ISSUES...On Wednesday September 28 2016... Unhealthy
for sensitive groups in Fresno and Kings Counties. Further
information is available at Valleyair.org
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.