Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 292214
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
314 PM PDT Fri May 29 2015
Above normal daytime temperatures today and Saturday as high
pressure slides across the west coast. Cooler early next week with
a slight chance of showers and thunderstorms over the northern
Sacramento valley and surrounding mountains as the tail end of a
Pacific trough brushes through. Warmer temperatures may return
mid to late in the week.
Ridge of high pressure over the area today bringing above normal
temperatures and mostly sunny skies with high clouds moving
through the area. Temperatures this afternoon are running similar
to several degrees warmer than yesterday. High temperatures will
be in the upper 80s to mid 90s in the Valley and mid 60s to low
80s in the mountains this afternoon. These temperatures are
generally around 5 to 10 degrees above normal for the end of may
and will be close to what we saw at the beginning of the month
and in some places may be the warmest so far this year.
Temperatures will be similar to slightly cooler tomorrow as the
ridge axis begins to shift to the east and an upper level trough
approaches the west coast.
The upper level trough and associated low pressure system will
strengthen the onshore flow and deepen the marine layer Sunday
into Monday bringing cooler temperatures and possibly some low
clouds into the Valley. This system will also bring some
instability for a chance of showers and thunderstorms over the
Coastal Range Sunday afternoon and spreading into the Northern
Sacramento Valley and the rest of the surrounding mountains by Monday.
High temperatures are expected to reach the mid 70s to low 80s
in the Valley and 50s and 60s in the mountains on Monday which is
several degrees below normal for the first of June.
.Extended Discussion (Tuesday through Friday)
The weekend upper trof is forecast to lift Nwd and out of our CWA
late Tue. Will continue the mention of mainly lingering showers
over our Nrn Mtn zones on Tue before drier WNWly flow prevails on
Wed. From there...the medium range models diverge with multiple
solutions. The GFS/GEM are generally in better agreement today. The
ECMWF forecast of an "inside slider" system affecting Norcal
during the Thu/Fri period is met with a high degree of uncertainty
given the amplification of the W coast trof compared to the
GFS/GEM. Also...the loop of the ECMWF 5H dprog/dt illustrates
the high degree of model variability/inconsistency. This more
amplified solution would give Norcal higher PoPs and cooler temps
if this solution were to evolve and verify. For now we are leaning
toward the consensus of the GFS/GEM and a more seasonable wx
pattern. The high temp forecast of 5 degrees cooler than normal on
Tue is expected to modify to near normal for Wed thru Fri. JHM
VFR SKC or occasional cirrus over interior Norcal with the upper
level ridge shifting Ewd into the Great Basin. Stratus along the
coast with tops up to 2 kft forecast to move inland west of KSUU
after 08z with local MVFR/IFR cigs. Marine layer not expected to
make progress into Srn Sac Vly Sat and Sun mornings due to weak
onshore gradients and suppression of ML by large scale subsidence.
Local SW wind gusts to 25-30 knots through Carquinez Strait/Delta
at times tonight and Sat.