Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Joaquin Valley - Hanford California
341 PM PDT Thursday Jul 31 2014
Update...updated air quality issues section.
high pressure and above average temperatures will continue through
the weekend. A daily threat of isolated showers and thunderstorms
will continue through Monday over the Sierra crest. Afterward...high
pressure will weaken as a trough of low pressure moves into the
Pacific northwest and allow a dry southwesterly flow to prevail over
Discussion...high amplitude upper ridge extending from the Desert
Southwest through the Great Basin into the inter-mountain west
region is the most significant weather feature impacting our area
today. The expansion of this large ridge and and drying of the
middle/upper levels have provided for a noticeable warming trend over
the southern Sierra Nevada with temperatures running well above
yesterday at this time. Over the San Joaquin Valley...temperatures are
generally running 3-5 degree f above yesterday. The triple digit heat is
expected to be the rule across the San Joaquin Valley...southern
Sierra foothills and the Kern County deserts through the upcoming
weekend as little change in airmass is expected. The daytime
warming over the higher elevations has provided for enough
instability for showers and a few embedded thunderstorms over the
southern Sierra Nevada where convective available potential energy and residual moisture have been
sufficient for convection to take place today.
Infrared imagery is indicating some high clouds off the socal coast
which are poised to push through our area tonight and early
Friday...but should have little impact for our area. Of greater
concern is smoke from the French...Dark Hole and El Portal wild
fires. Visible imagery indicated some smoke from these fires
drifted into the southern Sierra foothills and the east side of
the San Joaquin Valley. Have expanded on the aerial coverage of
smoke in the grids as a result as with little change in
airmass...smoke will impact portions of our area for the next few
days. Some isolated afternoon thunderstorms will be possible near
and along the southern Sierra Nevada crest over the next few days
as instability and cape will be sufficient for convection.
The WRF has been consistent from run to run at showing a surge of
tropical moisture pushing north along the back side of the
southwestern Continental U.S. Ridge over southeastern California by Saturday.
However...a deepening trough off the California coast will keep a dry
southwest flow across central California. Middle level moisture as noticed
from the 850-700 mb relative humidity forecasts and the 850 mb dew points will not be
sufficient enough for precipitation over Kern County and
indicate that the deeper moisture will remain to the east of our
County warning forecast area. However...later shifts will need to monitor in the case
this tropical surge is stronger than advertised and clips our
eastern portion of the Kern County mountains and deserts. Do
anticipate increased high clouds at times over the weekend most
noticeably over the Kern County deserts and over the higher
elevations of the southern Sierra Nevada.
The medium range models are in fair agreement and indicate the
ridge will flatten then re position itself over northern
Baja California...interacting with a deepening upper trough off the California
coast. This will result in a more pronounced dry southwest flow
over central California for much of next week. As a result...any residual
moisture over the southern Sierra Nevada will be pushed well to
the east of our County warning forecast area by the middle of next week. A slight cooling
trend is anticipated as well with increased onshore flow...but
temperatures will remain a little above seasonal normals. Not
much confidence in the extended period due to the uncertainty with
the weekend tropical surge and the position off the offshore trough
isolated thunderstorms with local MVFR conditions possible over the
southern Sierra Nevada through 06z Friday. Areas of MVFR visibility
in smoke over the lower elevations of the Sierra Nevada and
foothills. Otherwise...VFR conditions will prevail across the
central California interior during the next 24 hours.
Air quality issues...
on Friday August 1 2014... unhealthy for sensitive groups in
Fresno... Kern and Madera counties.
Further information is available at valleyair.Org
The level of certainty for days 1 and 2 is high.
The level of certainty for days 3 through 7 is low.
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 07-31 114:1908 83:1976 81:1908 53:1895
kfat 08-01 112:1908 79:1933 86:1908 56:1888
kfat 08-02 112:1908 83:1953 82:1908 53:1956
Kbfl 07-31 110:1943 60:1916 79:1982 55:1905
kbfl 08-01 112:1979 86:1985 80:2000 53:1912
kbfl 08-02 109:1979 86:1976 84:1977 53:1912