Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
FXUS66 KHNX 191004
Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
304 AM PDT Sun Mar 19 2017
.SYNOPSIS...Above normal temperatures and dry weather will
continue through the weekend before unsettled weather returns
Upper level ridging over the region will keep temperatures well
above normal and mostly clear skies south of Fresno County through
Monday. High clouds are expected from time to time as a cold
front remains stationary to our north and will dissipate by
Models continue to advertise a Gulf of Alaska low center to bring
a cold front through the region Monday night through Tuesday
night. There is some indications of a sub tropical tap, but is
not a true Atmospheric River event. It is a normal winter type
system. QPF amounts are in the normal range with a winter system.
Snow levels are going to start out pretty high with the system
around 8000 feet on Monday night and lower to around 7000 feet by
Tuesday night. Snow amounts are around 8-12 inches above 8000 feet
for the event. Valley rain will be around 0.10 - 0.25 south of
Fresno County and 0.25 to 0.50 Fresno County northward. Isolated
thunderstorms are possible along the frontal passage on Tuesday
as SPC has us in a general thunderstorm risk on their Day 3
outlook. Strong prefrontal wind from the SE will also be a
potential hazard Tuesday. West side winds and potential downslope
winds near the Grapevine could make travel hazardous. Winds will
weaken as the front moves through later in the day.
The frontal system will push through late Tuesday before the
upper cold pool will cross the region during the day on
Wednesday. Very unstable atmosphere expected with MUCAPE 400-800
j/kg and an upper trough moving through to act as a trigger for
thunderstorm activity. Timing is critical as more daytime heating
will increase lapse rates and break through a weak cap indicated
by the forecast soundings. Cloud deck could limit intensity of
storms, but some could become strong with hail, frequent
lightening and heavy rain being the threats. Some minor street
flooding could occur in stronger storms, however we are expecting
them to move rather quickly to the east, so widespread flooding is
Short wave ridging will allow things quiet down on Thursday in
the SJV. We are keeping a few showers in the Sierra with snow
levels down to around 4000 feet. No significant accumulation is
expected on Thursday. However west facing slopes could get a
couple of inches in heavy showers.
Strong cold front is expected to move into the region by early
Friday morning and continue all day with moderate to heavy
precipitation. Models are bringing up sub tropical moisture in
association with the cold frontal passage. The front is a slow
mover and we could see potentially significant rainfall across
the central California interior Friday and Saturday. Rainfall
amounts are still uncertain, but GFS guidance continues to show
a significant bullseye across the Sierra of 1-3 inches liquid.
Snow levels are forecast to be around 6000 feet for the event.
NW flow aloft will dry things out on Sunday with slightly cooler
temperatures across the area. A few showers are possible in
favorable upslope areas in the Sierra on Sunday. The SJV will be
dry and seasonal.
VFR conditions can be expected across the Central CA Interior during
the next 24 hours.
.AIR QUALITY ISSUES...
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.