Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 220405
Area Forecast Discussion
National Weather Service Sacramento CA
905 PM PDT SAT MAY 21 2016
An upper level disturbance will bring unsettled weather and cool
conditions this weekend across NorCal. There will be chances for
showers, thunderstorms, and mountain snow Sunday and Monday.
Temperatures will become warmer by mid week.
.SHORT TERM DISCUSSION...
Showers over the CWA now winding down as short-wave moving through
the longer-wave W Coast trof passes S of our CWA. One of the later
hourly HRRRx REF progs suggests the rest of the nite will be rain-
free over most of our CWA except for perhaps the NErn zones which
are closer to a weaker short-wave rotating around the upper low
center in Ern OR.
The next upstream short-wave forecast to bring a return of showers
to our CWA is near VCRISL and will be dropping Swd into Norcal about
18z Sun. Chance PoPs return primarily to the Mtns and Nrn Sac Vly on
Sun with isolated valley showers and scattered showers for the
mountains. Isolated thunderstorms will also be possible over the
mountains. Low pressure will remain over the region at least through
Tuesday with unsettled weather continuing for the interior. Most of
the activity early next week looks to occur in the mountains with
isolated activity for the valley. /JHM
.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)
Unsettled weather pattern continues in the extended forecast
with below normal temperatures. From Tuesday evening into
Wednesday, a trough will extend over our region with a closed low
just south of our forecast area. This will keep a chance of
showers and thunderstorms in our region, mainly over the
mountains. The trough and low will move eastward by Wednesday
night so that by Thursday, the trough axis will be just east of
our CWA. Lingering moisture from the backside of the trough will
continue to impact our area with a chance of showers and
thunderstorms mainly over mountains and north of Interstate 80. On
Friday, models vary, but both the ECMWF and GFS show another low
pressure system moving across the Pacific NW and possibly skirting
NorCal. Not confident in details, yet, but have left a chance of
showers in the northeastern portion of our CWA for Friday.
An upper level disturbance will remain over NorCal the next 24
hours. Mainly VFR conditions are expected across Valley TAF sites,
while periods of MVFR/IFR conditions will prevail over the
mountains with intermittent showers. Winds will generally remain
south to west below 10 kts.