Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Joaquin Valley - Hanford California
246 PM PDT Wednesday may 6 2015
other than isolated thunderstorms along the Sierra crest early this
evening...dry weather can be expected over the district tonight. A
storm system will bring wintery weather to the highest elevations of
the Sierra Thursday through Friday with showers and isolated
thunderstorms in the lower elevations. Dry weather and warmer
temperatures will return this weekend as a ridge of high pressure
builds into central California.
Discussion...mostly clear skies and cooler temperatures were
observed through the region today as a storm system centered over
Washington and Oregon continues to move slowly south toward the
area. Temperatures through the San Joaquin Valley...the Sierra
Nevada foothills...and the desert were generally in the middle 70s to
low 80s...a few degrees below normal for the beginning of may.
Clouds have formed over the Sierra Nevada this afternoon with the
daytime heating. However...the upper level winds are blowing from
west to east...all activity is quickly moving to the east of the
crest. The high res arw and nmm as well as the hrrr keep all
chances of precipitation to the east of the region...adding
confidence that the area will not see any activity through at
least early Friday morning.
Big changes in the weather pattern are in store for the area
Thursday into Friday...as colder late season storm impacts the
region. The operational runs and ensemble means are all in good
agreement about the track of an upper low currently impacting the
Pacific northwest heading south into northern California. By early
tomorrow (thursday) morning...the center of the upper low will be
over northern California with the southern extent over the San
Francisco Bay. Showers will spread south over the central Sierra
Nevada early Thursday morning and continue spreading south
impacting the entire Sierra Nevada by the late morning hours. As
the center of the low tracks south southeast through the
region...showers will be possible through much of the region
during the afternoon and early evening hours.
By early Friday morning...the upper low will stall over the
southern Sierra Nevada...with showers continuing mainly over the
mountainous regions...including the west side of the valley and
the Kern County mountains.
Snow levels with this system will start around 7,500 feet late
tonight into early Thursday morning and fall to around 6,000 feet
by late Thursday morning as cold air filters into the area behind
the upper low. A few inches of snow will be possible above 6,000
feet between Thursday late morning and Friday evening. Up to 6
inches of snow will be possible in isolated areas with the
heaviest showers. The Winter Weather Advisory was expanded to
include the southern Sierra Nevada above 6,000 feet.
Additionally...an unstable airmass will accompany this
storm...with thunderstorms possible Thursday afternoon into the
evening hours. Surface cape values peak between 350 and 800 j/kg
through the entire region according to the high res arw...the
NAM...and the GFS...adding to forecaster confidence for at least
isolated thunderstorms. With any thunderstorms...especially in the
Sierra Nevada...a quick few inches of snow will be possible...even
lower than the 6,000 foot snow levels. Those planning a
backpacking or hiking trip to the Sierra Nevada should plan
By Friday night...the upper low will slowly shift east out of the
region...leaving behind a few scattered showers over the Sierra
Nevada...with dry weather elsewhere.
Upper level high pressure will briefly build over the region over
the weekend resulting in a warming trend and dry weather.
Another cooling trend will be present during the first part of
next week as an upper low shifts south southeast toward northern
California from the Pacific northwest coastline. This storm is
forecast to keep any chance of precipitation to the north of the
showers and isolated thunderstorms will be possible over the crest
of the southern Sierra Nevada this afternoon. Otherwise...VFR
conditions will prevail across the central California interior for
the next 24 hours.
Air quality issues...
The level of certainty for days 1 and 2 is medium.
The level of certainty for days 3 through 7 is high.
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 05-06 100:1987 58:1921 69:1992 41:1975
kfat 05-07 103:1987 56:1905 69:1989 36:1965
kfat 05-08 101:2001 59:1977 71:1987 39:1933
Kbfl 05-06 104:1987 55:1921 71:1989 42:1988
kbfl 05-07 101:1987 61:1930 70:1989 42:1965
kbfl 05-08 100:1987 63:1933 71:1906 40:1908
Winter Weather Advisory from 11 am Thursday to 5 PM PDT Friday