Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Joaquin Valley - Hanford California
235 PM PDT Friday Apr 17 2015
Synopsis...high pressure over the area is producing mainly dry
conditions and above average temperatures into the weekend for the
valley and foothills. A threat of thunderstorms does exist over
the crest of the Sierra Nevada during the weekend and into Monday.
A change in the weather pattern may be possible next week as a low
pressure area moves in from the Pacific. This may bring a threat
of showers and thunderstorms to central California beginning
Discussion...dry upper ridge centered off the California coast is
providing our area with another dry day under mainly clear skies
and light winds along with a continued warming trend. The
mountains and Kern County deserts are trending 6-12 degree f above
yesterday at this time and the San Joaquin Valley and southern Sierra
foothills are generally running 4-8 degree f above yesterday is response
to rises in heights and diurnal thicknesses.
12z WRF indicating the ridge will build inland tonight and
satruday as the large closed upper low over The Four Corners
region lifts northeast. The ridge is then prognosticated to amplify on
Sunday and Monday while some shortwave energy undercuts the ridge
and forms a Rex-block pattern over the western Continental U.S.. middle/upper
moisture from the undercutting energy along with increasing
instability and cape each day will allow for increasing chances of
mountain convection satruday through Monday wit the best chances
near and along the crest on Sunday and Monday afternoon where
there will be a chance of showers and a slight chance of
thunderstorms. Meanwhile...dry conditions along with unseasonably
warm temperatures will prevail over the San Joaquin Valley and
Kern County deserts through Monday.
The medium range models are advertising the Rex-block pattern to
break down on Tuesday as a negatively tilted trough approaches
the California coast. The GFS has been advertising an upper low center to
eject southward from the main trough on Wednesday then move
slowly east across the Great Basin on Thursday and Friday.
Meanwhile...the European model (ecmwf) drops the low southward off the California coast on
Wednesday then ejects it east across socal on Thursday. Being that
a Rex-block is usually difficult the break down...our forecast
trends more toward the European model (ecmwf) which is slower with breaking down
the Rex-block and keeps most of the energy offshore. Temperatures
will trend cooler next week from Tuesday Onward and there will be
increased precipitation chances throughout our area on Wednesday
and Thursday. There will also be at least a slight chance of
thunderstorms nearly anywhere across our area on Wednesday as a
cold front pushes through. Exactly which areas will be impacted by
precipitation and how much rainfall or mountain snowfall will
accumulate is very difficult to pinpoint at this time and bring
that a blocky pattern will exist ahead of this system which the
models are often notoriously too aggressive in breaking down. As
a result...confidence in the forecast for Wednesday through Friday
remains low at this time.
Aviation...VFR conditions and light winds can be expected
throughout the central California interior during the next 24
Air quality issues...none.
The level of certainty for days 1 and 2 is medium.
The level of certainty for days 3 through 7 is low.
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 04-17 94:1980 58:1933 58:1992 34:1896
kfat 04-18 95:1910 51:1955 62:1939 36:1941
kfat 04-19 93:2009 54:1967 64:1938 35:1955
Kbfl 04-17 95:1954 60:1975 61:1954 34:1922
kbfl 04-18 98:1910 55:1923 63:1954 35:1922
kbfl 04-19 98:1910 54:1967 62:1938 38:1996