Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 210410
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
910 PM PDT Mon Apr 20 2015
Threat of afternoon and evening showers and thunderstorms...
mainly over the mountains...will continue through the week with
gradual cooling trend.
Isolated showers still linger over Plumas County and south of
Yosemite NP but should be tapering off in the next couple of
hours. A strong delta breeze is on going this evening and has
helped to cool inland temperatures 3 to 8 degrees over yesterdays
temperatures at this time. The delta breeze is expected to
continue overnight. As the lower atmosphere moistens up some low
clouds may form around the Sacramento area in the morning.
High pressure circulation to the north helped to push some of the
earlier activity westward today. The area will drift east slightly
for Tuesday while a weak low pressure circulation moves over
Southern California. This may help to continue to push shower and
thunderstorm activity towards the west during the afternoon hours.
A trough will also deepen along the coast. Instability looks very
good again on Tuesday for more showers and thunderstorms.
The trough axis moves along the coast Tuesday night and may be
able to keep some showers activity going all night in the
mountains. On Wednesday the low pressure area through that was
along the coast will move into the Pacific Northwest while the low
pressure area over Southern California retreats further to the
south. Instability and available moisture look to continue the
shower and thunderstorm activity. We will have to keep an eye out
for possible showers or isolated thunderstorms to drift over the
valley during the Tuesday night through Wednesday night time
On Thursday the low that was over Southern California will move
east to over the desert southwest. Another weak trough from the
Gulf of Alaska will move through Thursday night into Friday
morning to keep the threat of some shower activity going.
.Extended Discussion (Friday through Monday)
A shortwave trough will have moved into Nevada by Friday with a
flat ridge overhead. However, enough instability and orographic
flow will remain to generate some showers mainly over the
Sierra/Cascades Friday/Saturday. The flat ridge will strengthen a
bit through the weekend, bringing warmer and drier weather.
Previous medium range model runs had hinted at a stronger trough
moving through Northern California early next week. However,
latest runs have kept the bulk of moisture primarily to our north.
We`ve trended down our precipitation forecast chance accordingly.
Mainly VFR conditions for the next 24 hours. Isolated
afternoon and evening thunderstorms will return over the Sierra
and Coastal Range aft 20z. A 50 percent chance MVFR stratus may
reach Sacramento TAF sites between 10-16z. Near the Delta,
southwest winds 20-32 kt will continue overnight.