Riverdale, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

201
FXUS66 KHNX 210544
AFDHNX

Area Forecast Discussion
National Weather Service Hanford CA
944 PM PST Sat Dec 20 2025


.KEY MESSAGES...

1. A Flood Watch is in effect for the Sierra Nevada below 9,000
feet and foothills, mainly Yosemite, as well as Mariposa and
Madera Counties until Monday.

2. A significant pattern change is expected to take place by this
evening with precipitation likely for the Sierra Nevada and its
foothills from Fresno County northwards. Moderate to briefly
heavy precipitation is possible in these areas from this evening
into Sunday.

3. A second, stronger system is expected to arrive Tuesday, with a
moderate risk for heavy precipitation throughout Central California,
and a moderate risk for heavy snow in the Sierra Nevada
expected from Christmas Eve through Friday of next week.

&&

.DISCUSSION...
Showers have mainly passed to the north of our forecast area so
far this evening, although expect some southward movement later
tonight into Sunday morning. Another band of precipitation will
also arrive later on Sunday. The best chances for measureable
precipitation remain near Yosemite NP, currently at 70-80
percent, with snow levels above 9,000 feet until Monday. Until
Sunday, chances for precipitation lower in the San Joaquin
Valley, including a 40-50 percent chance towards Merced County
while probabilities remain below 15 percent mainly south of
Fresno County through Monday. Precipitation chances retreat
northward a bit on Monday afternoon into early Tuesday morning
before the next system arrives.

The initial surge of moisture and southerly flow associated
with the system on Tuesday arrives Tuesday morning and gradually
progresses inland over our region by the afternoon. Along this
front, a plume of moisture from the tropical Pacific Ocean will
traverse into our area. Precipitation begins in earnest over our
entire forecast area by later Tuesday afternoon. Chances
continue through at least Friday. The bulk of the precipitation
occurs Christmas Eve and Christmas Day and tapers off a bit
Thursday night into Friday. Snow levels lower to 7,000-8,000
feet on Tuesday and gradually lower to 6,000 feet by the evening
of Christmas Day. Probabilities for at least one inch of
precipitation per 24 hours each day ending Wednesday afternoon
and Thursday afternoon are currently at 50-60 percent in the San
Joaquin Valley and Kern County desert, and 90 to near 100
percent over much of the higher terrain into the lower
foothills. As for 2 inches per 24 hours on each day, the
probabilities are much less for the valley and desert (10-20
percent), but remain at 80-90 percent for the Sierra Nevada and
adjacent foothills. This is generally due to the orographic
nature of precipitation that is typical with these atmospheric-
river type of systems. In addition to the threat of heavy
precipitation, we are monitoring for increased southerly winds
that could produce strong enough gusts to knock over trees.
The probability for a 40 mph gust in the Central Valley is as
much as 30-40 percent towards Merced County with even greater
chances in the coastal ranges (50-60 percent). The time frame is
from Tuesday until Christmas Day for winds this strong.

By Friday, the cold front passes, although an upper-level trough
remains into the following weekend that will produce lingering
showers. Above average precipitation remains favored in our
area beyond next weekend, although the chances have lowered
compared to the last couple of days. The 6-10 day outlook shows
about a 40-50 percent chance, while the 8-14 day outlook lowers
to 33-40 percent. Above average temperatures are at around 40-50
percent for both periods.

&&


.AVIATION...
MVFR conditions are expected for mainly northern portions of
the San Joaquin Valley during the next 24 hours with a slight
chance of showers around MCE and MER 16Z-20Z Sunday. IFR
ceilings due to precipitation over the Sierra Nevada and
adjacent foothills from Fresno County northward. Otherwise, VFR
conditions will prevail over the next 24 hours.

&&

.AIR QUALITY ISSUES...
On Sunday December 21 2025, Fireplace/Wood Stove Burning Status is:
No Burning Unless Registered in Fresno, Kern, and Madera
Counties. Burning Discouraged in Kings, Merced, and Tulare
Counties, and Kern (Greater Frazier Park Area) and Sequoia
National Park and Forest.



&&

.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.html for additional information
and/or to provide feedback.

&&

.HNX WATCHES/WARNINGS/ADVISORIES...
Flood Watch from Tuesday afternoon through Friday afternoon
for CAZ300>317-319>322-327>339.
Flood Watch through Friday afternoon for CAZ318-323>326.
Winter Storm Warning until 4 PM PST Friday for CAZ323.
Winter Storm Watch from Tuesday afternoon through Friday
afternoon for CAZ326>331.
&&

$$

BSO

weather.gov/hanford