Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Joaquin Valley - Hanford California
342 am PDT Thursday Sep 18 2014
Synopsis... an approaching low pressure system will lower
temperatures to near normal today and Friday. Temperatures will rise
above seasonal normals by Saturday. There will be a slight chance of
showers and thunderstorms over the higher sierras through
Discussion...main feature of concern this morning is a fairly
strong upper trough approaching the California coast. WV imagery and GOES
high density winds are indicating an upper low pressure center
currently situated near 41n/127w which is taking aim at the
norcal coast. Relative humidity forecasts are indicating that this system will not
have much moisture associated with it as it pushes through
central California later today and tonight. However...it will provide for
a very noticable cooling trend today as temperatures are expected
to lower to near seasonal normals today in response to lowering
heights and thicknesses. Any precipitation associated with this
system today will likely be confined to the Yosemite park area
where there will be marginal instability and cape for convection
to take place this afternoon as per the 00z and 06z WRF runs. The
high resolution WRF is indicating the potential for another brief
period of breezy to locally windy conditions again tonight along
the west side of the San Joaquin Valley and over the passes of
the Kern County mountains and deserts.
The trough is prognosticated to move east of the region on Friday...but
the upper low is prognosticated to break off and form a cut off low off
the central California coast and drop slowly southward through Friday
night and remain stationary off the socal coast on Saturday. The
low is then prognosticated to lift slowly northeast and cross our area
by Sunday. The proximity of this upper low will maintain enough
instability over the area for a slight chance of thunderstorms
each day over the southern Sierra Nevada...mainly along the
crest. At this time this system is not expected to have sufficient
moisture for precipitation elsewhere in our County warning forecast area...but if any
tropical moisture becomes entrained in the upper low on satruday
while it is off the socal coast...the potential may exist for
some sprinkles or light showers nearly anywhere in our County warning forecast area on
Saturday night and Sunday. Temperatures are prognosticated to remain near
seasonal normals on Friday then rise slightly over the weekend as
noticable rises in middle level temperatures are anticipated.
The medium range models are in good agreement in ejecting the
upper low well to the northeast of our area by Monday as a dry
upper ridge pushes inland. The ridge is prognosticated to amplify over
the Great Basin through Wednesday which will leave our area under
a dry southwest flow between the Great Basin ridge and another
upper trough that will impact our area toward the end of the
period. As a result...temperatures will rise upward to well above
seasonal normals again for Monday through Wednesday. The models
are in disagreement with their handling of the next trough as it
moves inland next Thursday. The ecwmf is much deeper with it and
if it were to pan out a sharp cooling trend would take place
toward the end of next week along with showery conditions.
However...the GFS is not as deep with the trough and are not as
pronounced with the cooling trend advertised by the ecwmf and
keep any precipitation associated with it to the north of our
Aviation...VFR conditions will prevail across the central California
interior during the next 24 hours.
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 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 09-18 107:1913 67:1963 78:1984 48:1978
kfat 09-19 105:1922 70:1989 75:1984 44:1978
kfat 09-20 104:1939 73:2007 73:1939 46:1978
Kbfl 09-18 104:1913 69:1967 73:1984 45:1908
kbfl 09-19 104:1939 69:1989 73:2009 39:1908
kbfl 09-20 104:1899 73:2007 70:1974 38:1908