Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
FXUS66 KHNX 271020
Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
320 AM PDT TUE SEP 27 2016
.SYNOPSIS...Much above normal temperatures will continue today,
but a gradual cooling trend will take place this week. Highs will
fall back to near normal by Friday then several degrees below
normal by the weekend. A surge of tropical moisture will bring a
slight chance of showers and thunderstorms to the mountains and
deserts on Wednesday.
.DISCUSSION...Clear skies, offshore flow and an unseasonably warm
airmass continue to prevail across our area as Central CA remains
situated in between high pressure centered over the Great Basin
and an upper low centered just off the Baja coast near 27N/115W.
00Z and 06Z WRF runs are indicating the low will track northward
over northern Baja today and into southeastern CA by Wednesday.
The low will provide for some synoptic cooling across our area as
heights and thicknesses slowly lower although temperatures will
still be well above seasonal normals. The main impact this low
will have; however, is that it will up pull some moisture from
Tropical Storm Roslyn (currently situated near 18N/118W and moving
slowly northeast) and wrap it around into Central CA by Wednesday.
The WRF is showing enough instability and CAPE for a slight
chance of afternoon and evening thunderstorms over the mountains
and Kern County deserts although the WRF is now indicating that
the moisture and instability will remain to the south of Yosemite
Meanwhile, an upper low off the BC coast on Wednesday is progged
to deepen off the PAC NW coast on Thursday. This will result in a
strengthening onshore flow over Central CA which will push the
tropical moisture east of our area. By Friday the low will begin
to push inland across the PAC NW which will push a strong cold
front through our area on Friday Night resulting in much cooler
temperatures and a period of increased winds across portions of
The medium range models are in good agreement with pushing the
trough axis through our area on Saturday with a secondary system
dropping behind it early next week. Ensemble means and the GFS
keep the deeper moisture with this feature to the north of our
area so for now will keep a dry forecast for early next week.
Temepratures will plummet to below normal reading over the weekend
with highs in the San Joaquin Valley mainly in the upper 70s on
both days. A slight recovery is anticiapted for early next week,
but temperatures will remain slightly below seasonal normals.
.AVIATION...VFR conditions will prevail over the Central CA
interior during the next 24 hours.
.AIR QUALITY ISSUES...On Tuesday September 27 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.