Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Joaquin Valley - Hanford California
1009 PM PDT Tuesday Aug 19 2014
Synopsis...an upper level low centered just offshore the central
California coast will track southward to Point Conception by late
tonight then move inland across Southern California Wednesday.
Wraparound moisture associated with this system will bring middle
and high clouds to much of the district through midweek with a
slight chance of thunderstorms to the mountains and desert.
convection continues to fire-up over the Sierra Nevada and
adjacent foothills this evening with light rain being reported.
Currently...activity remains from Fresno County northward...and
mostly clear over the south end. Short range ensemble models
showing precipitation confined to area north of Tulare and Kings counties
overnight and spreading to area near Kern County on Wednesday.
Therefore...updated the sky cover grids to reflect the cloud
coverage trend overnight and early Wednesday. Will see a return of
convection on Wednesday afternoon...yet weaker...as the upper low
continues to drop toward Southern California toward midweek. At
this point...will only update the cloud cover (sky) grids.
Previous discussion... /issued 150 PM PDT Tuesday Aug 19 2014/
500 mb low positioned just offshore the central California coast will add
complexity to the forecast during the next 48 hours. Middle and high
level moisture will continue to wrap around this low and bring a
considerable amount of cloudiness to much of the County Warning Area tonight and
Wednesday. Difluence aloft combined with modest lift will produce
isolated showers/thunderstorms over the Sierra generally north of Kings
Canyon through this evening. An easterly flow aloft could bring
very light rain or sprinkles into a few foothill and sj valley
locations from Fresno County north tonight into Wednesday morning.
Otherwise...the models track this low as a coastal hugger to just
south of Point Conception tonight then move this system inland into
Southern California Wednesday where it is forecast to remain nearly idle
through Thursday. As mentioned in the earlier discussion...there is
concern that this low will tap into some subtropical moisture. If
so...this moisture will become entrained in its counterclockwise
circulation and produce a more favorable environment for convection
over the mountains and desert from Wednesday afternoon through
Thursday evening/night. Sky cover was increased somewhat in the
gridded forecast for the next 24 hours and probability of precipitation were bumped up a bit
in the upslope portion of the Kern County mountains and in the
Kern County desert for Wednesday into Wednesday evening to match
up with weather forecast office lox. Beyond this period...confidence remains low
regarding the convective potential over the higher terrain and it
will depend on where this low tracks and how much if any additional
moisture it draws northward.
Epac ridge slides in from the west as the low center moves into
Arizona on Friday. Gradual warming trend for the weekend is expected
with dry conditions returning. Strong upper level low center moves
into the Pacific northwest and kicks east. A trailing trough will push into
northern California on Sunday night and actually looks like it will interact
with the remnants of Lowell near 30n and 130w on Monday. It is a
bit too far out to predict where tropical systems will track and
how the residual moisture of Lowell will interact with the trough
on Monday...but looks interesting right now for possible
clouds/rain showers across the cencal region on Monday if current model
runs play out. Forecaster confidence is low with this feature.
Aviation...isolated thunderstorms are possible over the higher
elevations of the southern Sierra through 06z Wednesday and over
the mountains and desert after 19z Wednesday. Otherwise...VFR
conditions will prevail across the central California interior
during the next 24 hours.
Air quality issues...
The level of certainty for days 1 and 2 is high.
The level of certainty for days 3 through 7 is medium.
This information is provided as part of a trial project conducted
by the National Weather Service San Joaquin Valley - Hanford.
Certainty levels include low...medium...and high. Please visit
www.Weather.Gov/hnx/certainty.Php /all lower case/ for additional
information and/or to provide feedback.
site date hi_max:year lo_max:year hi_min:year lo_min:year
Kfat 08-19 108:1892 67:1976 74:2012 54:1916
kfat 08-20 108:1919 76:1959 75:1986 54:1974
kfat 08-21 108:1919 80:1968 76:1913 51:1959
Kbfl 08-19 109:1950 78:1959 79:1961 52:1913
kbfl 08-20 112:1950 77:1959 79:1950 52:1912
kbfl 08-21 110:1919 80:1968 77:1982 51:1918