Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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FXUS66 KHNX 231230
AFDHNX

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
430 AM PST Mon Jan 23 2017

.SYNOPSIS...A cold and unsettled airmass will prevail over the
area today and provide for numerous showers and a chance of
thunderstorms. A drying trend will begin on Tuesday although
isolated showers will still be possible. High pressure will
provide for dry conditions on Wednesday then a weak system will
bring increased clouds and some light mountain showers to the
area on Thursday. An upper ridge will then prevail over the area
Friday through the weekend with dry weather and seasonal
temperatures.

&&

.DISCUSSION...A cooler and unstable post-frontal airmass now
prevails over central CA with radar composites showing numerous
showers over the southern Sierra Nevada and scattered showers over
across much of the remainder of our area. A few lightning
strikes were even noted in the Tulare County Mountains overnight.
The strong winds that prevailed across our area on Sunday have
diminished over the lower elevations while a few of the higher
peaks in the Tehachapi Mountains have still have gusts between 35
and 50 mph.

Meanwhile, a deep upper low center off the OR coast near 45N/130W
continues to keep a moist southwest flow over central CA which is
providing ample moisture for a continuation of showers across our
area. The 06Z WRF is indicating the large upper low will drop
southeast today to off the Norcal coast which will keep our area
under a very unstable airmass today. WRF is indicating LI`s of -4
to -2 Deg C and CAPES of 400 to 800 J/KG over the San Joaquin
Valley this afternoon with CAPES between 200 and 400 J/KG across
the remainder of our area. Have mentioned a chance of
thunderstorms across the valley this afternoon and a slight chance
across the rest of our area. Would not be surprised if some
thunderstorms contain ice pellets and/or small hail as low
freezing levels prevail. Webcams are already indicating snow
falling as low as 2500 feet this morning over the southern Sierra
foothills although by this afternoon enough diurnal warming
should take place for the snow level to rise to 3000 to 3500
feet. A winter storm warning remains in effect for the Southern
Sierra Nevada and the Kern County Mountains through 10 am PST this
morning as the potential still exists for impacts to travel from
heavier snow showers.

The low is progged to move inland across Norcal tonight and
Tuesday which will keep the potential for showers across our area
through Tuesday afternoon. Snow levels are progged to drop to 2000
to 3000 feet tonight then rise to 3000 to 4000 feet by Tuesday
afternoon.

Shortwave ridging is then progged to build into central CA on
Tuesday Night and provide our area with dry conditions on
Wednesday along with with clearing skies. However, some patchy
fog will be possible in the San Joaquin Valley with the lower
levels remaining very saturated. The WRF is now showing a weak
shortwave pushing through our area on Thursday which will delay
then onset of any persistent fog as a keep the airmass from
stabilizing and may provide for a few showers in in the Yosemite
area.

The medium range models and their ensemble means are in fairly
good agreement with building a dry upper ridge over CA by the end
of the week which will keep a dry and stable airmass over our
regions through the upcoming weekend and into the early part of
next week. This will result in mainly clear skies and a noticeable
drying trend over the higher elevations while inversion
conditions become more prevalent over the San Joaquin Valley
providing for a return of night and morning fog from Friday
onward.

&&

.AVIATION...
In the San Joaquin Valley, generally VFR through 17z then areas of
of MVFR and local IFR in showers and thunderstorms

In the southern Sierra Nevada and adjacent foothills, mountain
obscuring IFR in low clouds and precipitation prevailing with areas
of LIFR.  Otherwise, VFR conditions will prevail during the next 24
hours.

&&

.AIR QUALITY ISSUES...None.

&&

.CERTAINTY...

The level of certainty for days 1 and 2 is medium.
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.

&&

.HNX Watches/Warnings/Advisories...
Flash Flood Watch until 10 AM PST this morning CAZ093>097.

Winter Storm Warning until 10 AM PST this morning CAZ096-097.

Winter Storm Warning until 10 AM PST this morning CAZ095.

&&

$$

public...DS
avn/fw...Dudley
synopsis...DS

weather.gov/hanford


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