Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 252239
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
339 PM PDT Wed Mar 25 2015

.Synopsis...
Dry and warm weather through the end of the week. Weak weather
systems will move though the far northern part of the state
starting this weekend into next week. Otherwise...dry and warm
weather conditions to continue.

&&

.Discussion...
Noon-time temps running some 11-14 degrees warmer than 24 hrs ago
from MYV Nwd...and 1-8 warmer from the Sac area...Swd into the
Nrn SJV. Nly flow from increasing Nly pressure gradients (up to 4
mbs) and building high pressure over the region also resulted in
adiabatic warming effects over the Nrn half of the CWA. The
strong ridge with greatest height anomalies from 700 to 200 mbs
will continue to build over Norcal through Thu. Near record or
record max temps possible both Thu and Fri especially in the Srn
Sac and Nrn San Joaquin Vly as maxes forecast to climb well into
the 80s throughout the Central Valley. Warmest day in the area on
Thu with the ridge axis forecast to be over the area...and then
primarily in the Srn Sac and Nrn San Joaquin Vly as the ridge axis
shifts inland and onshore flow develops. Will lean towards the
higher members of the NCEP SREF plume for maxes at some of the
sites for the next couple of days for the Srn locations...as the
Nrn locations appear not warm enough.

Upvalley flow from the approaching short wave is likely to lead to
some cooling in the Nrn half of the Vly...while the cooling
effects of the Delta Breeze are delayed a day in the Nrn SJV on
Fri. Warm wx also expected in the Mtns with cooling beginning Fri
in the coastal and Nrn Mtns...continuing into Sat and spreading
into the Siernev.

Approaching short wave weakens (What else would we expect?) as it
moves inland late Fri nite and Sat with chance PoPs limited
primarily to the Nrn mtns during the day and possibly near the
crest of the Siernev Sat evening. We leaned towards the GEM/ECMWF
solutions which show a much more progressive short wave moving
through Norcal than the GFS which cut-offs an upper low over
Norcal. This solution would be more showery/unstable for Norcal.
A strong Pacific jet/Wly flow into the Pac NW/B.C. area is
expected to lead to a progressive pattern.    JHM


.Extended Discussion (Sunday through Wednesday)

Some model differences are complicating the forecast for Sunday. The
ECMWF quickly exits a weak shortwave out of the area and rebuilds
the ridge, bringing a return to dry conditions and very warm
temperatures. The GFS is currently showing a closed low gradually
passing over the area on Sunday. This would bring the potential
for showers across much of the forecast area, with lingering
shower activity (and possibly convection) focused over the Sierra
by afternoon and evening. The GFS has had trouble over the past
few runs deciding how it wants to handle this low. For now, will
lean towards the drier, warmer, more progressive ECMF and GEM
models. Will keep just a slight chance of Sierra crest showers south
of I80.

Some high temperatures on Sunday and Monday could be record
breaking. The highest potential for records would be south of
I80, where sunshine combining with a warm airmass would bring
highs in the mid to possibly upper 80s. Cloud cover is expected to
be more extensive to the north, and could limit heating there some.

There is good agreement as weaker systems brushes by to the north
Monday night and Tuesday. Precipitation is expected to stay to the
north and west of the forecast area, with an increase in cloud
cover and a slight cool down being the main effects. An
additional wave passes by to the north on Wednesday, following a
similar path. Temperatures are still expected to be about 10 to 15
degrees above normal levels. EK

&&

.Aviation...

VFR conditions expected thru the period as high pressure builds
into the area. Few to sct high clouds possible with variable
winds generally less than 10 kts.


&&

.STO Watches/Warnings/Advisories...
None.
&&

$$






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