FXUS66 KSTO 152104
AFDSTO
Area Forecast Discussion
National Weather Service Sacramento CA
104 PM PST Sat Feb 15 2025
SYNOPSIS...
Aside from some light showers north of Interstate 80 throughout
the day on Sunday, dry and warming weather with occasionally
breezy winds is expected into next week. Additional light
precipitation chances possible across the middle of the week, with
a trend toward unseasonably warm weather then moving toward next
weekend.
.DISCUSSION
...
Amplified, yet transient, ridging aloft is expected across
interior NorCal today before a similarly quick moving shortwave
trough travels across the Pacific Northwest on Sunday. Despite the
ridging aloft, partly to mostly cloudy skies associated with the
approaching trough will keep high temperatures in the upper 50s to
low 60s throughout the Delta, Valley, and foothills, with 40s to
50s at higher elevations today. This cloud cover and attendant
increasing precipitation chances into Sunday will keep lower
elevation low temperatures in the lower 40s while 20s to mid 30s
prevail at higher elevations.
As far as temperatures go, highs for Sunday are expected to
remain similarly seasonable, with a potential degree or two upward
trend from Interstate 80 southward, where precipitation chances
will remain notably lower amidst weak warm air advection. While
precipitation chances are expected for most locations north of
Interstate 80, overall light precipitation totals are anticipated
as the center of the shortwave remains displaced further
northward. Precipitation totals of 0.1 to 0.25 inches are
expected, with highest totals at high elevations. Current
probabilities of exceeding 0.25 inches of precipitation sit around
5 to 15 percent for the aforementioned areas, with some 30 to 50
percent probabilities for far northern Shasta County. Snow levels
around 5000 to 6000 feet on Sunday will keep appreciable
accumulations confined to high elevations. With generally a
dusting possible down to 5000 feet, and 1 to 3 inches of snowfall
above 6000 feet.
As quickly as this system arrives, it is expected to eject out of
the region by midday Monday, leaving generally dry and warming
weather and occasionally breezy northerly winds in its wake moving
into the early week ahead. Similarly seasonable high temperatures
look to prevail into Monday, with a more notable warming trend to
the low to mid 60s across the Delta and Valley by Tuesday
afternoon as another transient ridge builds in. Even at their
breeziest, northerly wind gusts on Monday and Tuesday are only
expected to top out around 15 to 20 mph as well.
.EXTENDED DISCUSSION
(Wednesday THROUGH Saturday)...
Yet another quick moving shortwave around the midweek period will
further stymie any persistent warming trend until later in the
week. Current ensemble trends indicate that this trough will take
a slightly further southward trajectory as it progresses. If this
trend holds, attendant precipitation impacts would follow suit.
Precipitation totals will likely fluctuate as a function of the
trajectory ("heavier" precipitation with southward trend, lighter
precipitation with northward trend), the quick moving nature of
the shortwave will keep precipitation totals still relatively
light. Resultant probabilities of exceeding 0.25 inches of liquid
precipitation sit around 5 to 15 percent for most Delta, Valley,
and foothills locations, with 40 to 60 percent probabilities along
the Sierra and northern Sacramento Valley. A further southward
trajectory would also yield breezier northerly winds behind the
system, with some gusts up to 25 mph possible into Thursday.
Following this midweek system, there is near uniform agreement in
longwave, amplified ridging building in across the western CONUS
through the end of the week and into the following weekend. Exact
magnitude of the ridging aloft will determine the extent of
heating in this pattern, but a warming trend is expected to
accompany it regardless. While details will become clearer as the
week progresses, probabilities of some readings into the 70s
across the Delta, Valley, and foothills by Friday and Saturday sit
around 40 to 60 percent at this time.
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