Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 231030
Area Forecast Discussion
National Weather Service Sacramento CA
330 AM PDT MON MAY 23 2016
An upper level disturbance will continue to bring unsettled weather
and cool conditions across NorCal this week.
Clear to partly cloudy skies across interior NorCal early this
morning. Temperatures are pretty similar to readings from 24 hours
ago and generally range from the 30s and 40s in the mountains to
the upper 40s and 50s elsewhere.
Long-wave trough will remain in place over the West through the
period maintaining cool and unsettled weather for the region. Weak
circulation evident on satellite imagery to the west of the Bay
Area (37N/129W) is forecast to move toward central California
today and may provide the trigger for another upswing in shower
and thunderstorm activity by this afternoon. Most of the action is
expected over the foothills and mountains, but the HRRR is
indicating that some showers may develop in the Sacramento region
(NE quad of the approaching low) around the afternoon commute
Tuesday is expected to be quite similar to today as the weak low
continues to hang out over central California. With cloud cover
and a rather cool airmass remaining across the region,
temperatures will remain below average.
Less coverage of showers and thunderstorms are expected across
NorCal on Wednesday and Thursday as the low shifts south and east
of the area. Temperatures will gradually warm each day as the
airmass modifies and most areas see more sunshine.
.EXTENDED DISCUSSION (Friday THROUGH Monday)
The long term forecast period should begin dry for interior
northern California as a shortwave ridge of high pressure begins
to break down. High temperatures are looking to return to near
normal into the lower to mid 80s the valley and the 50s and 60s
for the higher elevations. Another upper level system is depicted
in model forecasts to slide across the Pacific NW Friday night
into Saturday, and a portion of the jet stream could clip
northern California. As a result, there will be the possibility of
some showers and isolated thunderstorms for northern portions of
the Sierra and southern Cascades for next weekend. Any snow
accumulations should remain confined to the upper elevations,
which should not affect mountain pass travel.
Model forecasts are in decent agreement as to the amplitude and
general timing pattern of the upper level low for next weekend,
however the progression differs slightly as to when the system will
clear northern California. Although there are slight differences in
the forecast scenarios, the beginning of next week should dry out as
a ridge builds back into the west from the eastern Pacific.
VFR conditions are expected for the terminals for the next 24
hours with light wind shifts. An upper level trough continues to
linger over northern California, which will result in BKN to OVC
ceilings for most flight times during the forecast period for the
Showers and thunderstorms today should stay confined
to higher elevations, although portions of the northern valley
near KRDD and KRBL could also see some shower or thunderstorm activity.
Confidence is low as to showers developing within the vicinity of
the terminals, so left mention out of the TAF for now.