Scientific Forecaster Discussion
fxus66 khnx 232115
Area forecast discussion
National Weather Service San Joaquin Valley - Hanford California
215 PM PDT Fri Jun 23 2017
Synopsis...a slight cooling will take place this weekend.
Thunderstorms will be possible over the southern Sierra Nevada
each afternoon and evening through the weekend. Dry conditions and
further cooling are expected next week.
Discussion...large upper ridge centered over southern nm
continues to remain the dominant weather feature for our area.
Temperatures have cooled 2-4 degree f from yday in the San Joaquin
Valley as a result of a shallow intrusion of marine cooled air.
Elsewhere across our area, temepratures have been running close
to yday. The excessive heat warning remains in effect for much of
our area through this evening although not as many daily records
are expected to fall today. WRF indicating instability and cape
will once again be sufficient enough for a slight chance of
thunderstorms near and along the southern Sierra crest this
afternoon and early this evening, but a light westerly flow will
help minimize the potential for any precipitation over the
The heat has continued to produce excessive snow melt over the
southern Sierra Nevada which resulted in rivers and streams
running high and fast. The rivers may look inviting during the
heat, but the cold and fast moving waters are extremely dangerous.
A Flood Warning is now in effect for increased releases from Pine
Flat dam on the Kings River and a flood advisory remains in
effect as a result of increased releases from Friant dam on the
San Joaquin River. Flooding has been observed along both rivers
The ridge is expected to weaken some this weekend resulting in a
slight cooling trend for our area. The exception being over the
Kern County deserts which will remain entrenched by the hot
airmass. An excessive heat warning remain in effect for the Kern
County deserts through Sunday evening while a heat advisory has
been posted for the San Joaquin Valley and foothill areas for
Saturday and Sunday as highs will still be in the triple digits,
but not approaching daily records like they have been for most of
the past week. Instability and cape will be sufficient for a few
afternoon and early evening thunderstorms on Saturday and Sunday.
The best chances will be from Yosemite np south to around Mount
Whitney where melting snow will provide for a moisture source.
The medium range models are in good agreement with the ridge
breaking down early next week as an upper trough pushes across the
Pacific northwest and norcal Monday and Tuesday. This will result in a
noticable cooling trend across our area with temperatures
lowering to near seasonal normals by Tuesday. A fairly pronounce
westerly flow will become established early next week which will
result in drier conditions aloft. This will inhibit mountain
convection from Monday Onward. Little change is expected next
Wednesday through Friday as a trough becomes established over the
Great Basin and a ridge amplifies near 135w which will keep a dry
northwest flow over central California.
Aviation...isolated thunderstorms are possible over the higher
elevations of the southern Sierra Nevada from 21z Friday to 04z
Saturday. Otherwise, VFR conditions will prevail across the
central California interior during the next 24 hours.
Air quality issues...on Saturday June 24 2017... unhealthy for
sensitive groups in Fresno... Kern and Tulare 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 medium.
Certainty levels include low...medium...and high. Please visit
www.Weather.Gov/hnx/certainty.Php for additional information
an/or to provide feedback.
excessive heat warning until 11 PM PDT this evening caz089>095.
Heat advisory from noon Saturday to 9 PM PDT Sunday caz089>095.
Excessive heat warning until 9 PM PDT Sunday caz098-099.