Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
FXUS66 KHNX 291013
Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
313 AM PDT SUN MAY 29 2016
A weak area of low pressure situated over southern California
will produce scattered showers and isolated thunderstorms over
the mountains today. Isolated afternoon thunderstorms are
still possible near the Sierra Crest on Memorial Day. Otherwise
dry weather will prevail over the district after this weekend
as a strong ridge of High pressure builds over the state. High
temperatures will average well above normal through Friday.
.DISCUSSION...Temperature-wise, it is payback time across central
California. After a spell of comfortably cool weather that lasted
from the 20th through the 25th, high temperatures have trended
a little warmer each day since. That`s a trend that will suredly
continue for the next few days as a strong ridge of high pressure
currently centered over the Eastern Pacific gradually builds over
the Golden State. That means triple digit heat is right around the
corner in the San Joaquin Valley and lower foothills. Until that
ridge becomes firmly established over central California,
thermometer readings will probably stay below the century mark
through Memorial Day even in the warmest locales. Subsidence
associated with the upper level ridge will also suppress afternoon
thunderstorm development over the Sierra beginning Tuesday.
Today will be the last truly active day for thunderstorms due
mainly to the presence of a weak upper level low over southern
California. Although moisture is rather limited with this low,
the models forecast impressive cape values of 800 joules/kg and
higher over the mountains this afternoon into this evening and
lifted indices of -2 C or greater. Winds aloft are very weak, so
thunderstorms that develop today will be slow moving and will
bring the possibility of locally heavy rain and minor flooding
to some mountain communities. Winds in the 700 mb to 500 mb
boundary layer will generally be east to northeast, so debris
clouds from dissipating mountain showers or thunderstorms could
easily end up in the foothills and the eastern and southern part
of the san joaquin valley toward evening. The upper level low
will get kicked into Arizona tonight as the epac ridge builds in
from the Pacific. Any thunderstorms that develop tomorrow aftn
will be few and far between and confined near the Sierra Crest.
Nonetheless, hikers and campers in the high country will still
need to keep a watchful eye on the sky Memorial Day afternoon.
Thunderstorms shouldn`t be much of a concern again until possibly
next weekend. In fact, the models depict a very interesting
scenario on days 6 and 7 and develop a closed low off the southern
California coast by Saturday. Winds aloft will be difluent over
central California next weekend, so if subtropical moisture gets
involved, we could be looking at the possibility of isolated
thunderstorms just about anywhere over the cwa next weekend,
particularly over the higher terrain. Considering that the GFS
and ECM are forecasting some QPF over the Sierra both of those
days, we`ve decided to introduce slight chance POPs along the
Sierra Crest next weekend. Adjacent WFO`s are in agreement with
this idea. Whatever the case, temperatures will still average
well above normal next weekend, but there might be a little added
humidity and sky cover, too. We`ll just have to wait and see how
the models handle that offshore low. Right now confidence is
pretty low on how the extended forecast periods will pan out.
Areas of MVFR and local IFR in showers and isolated thunderstorms
can be expected over the mountains between 20z today and 04z Monday.
Otherwise, VFR conditions will prevail over the central California
interior during the next 24 hours.
.AIR QUALITY ISSUES...
ON SUNDAY MAY 29 2016... Unhealthy for sensitive groups in Kern
and Tulare Counties.
Further informaiton 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 medium.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.php for additional information
an/or to provide feedback.