Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 081122
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
322 AM PST Sat Mar 8 2014
Dry and mild conditions continue today. A stream of Pacific
moisture will bring precipitation to the region Sunday and
Monday, especially for areas north of I-80. Breezy winds are
possible Tuesday. Dry and mild conditions return for the
remainder of the week.
Another warm day is on tap as the axis of an upper ridge moves
inland. Highs today should climb a few degrees from yesterday`s
readings per model guidance, especially over the mountains. The
only limiting factor on temperatures could be thickening high
clouds this afternoon associated with an EPAC moisture stream
approaching the West Coast. Current satellite PWAT estimates show
a healthy surge with a maximum of 1.6" PWAT near 135W or about
600 miles offshore from NorCal. The GFS has a decent handle on
this, but does appear to be slightly under-representing the
moisture with this plume.
An upper-level trough is expected to dig towards the Pacific NW
Sunday, pushing the moisture tap onshore during the day. The
plume then holds nearly stationary Sunday before finally pushing
southeastward early Monday as the trough moves inland. This
configuration puts the bulk of the rain north of I-80 Sunday. The
Shasta area, coastal mountains, and Feather River drainage should
see healthy precip totals with several inches of rain possible.
Meanwhile, Valley locations from Sacramento southward will most
likely see less than a quarter inch. Meanwhile, instability progs
do not look that impressive, but as the recent convective event
demonstrated we are getting into a favorable time of year for
thunderstorms and it doesn`t take much to get things going.
Convective parameters suggest Sunday afternoon chances are quite
slim, so have limited the previous forecast`s mention of thunder
to mostly the North Sac Valley. Monday afternoon looks like a
better bet with colder air moving in aloft and the trough axis
approaching, so left a slight chance of thunder for all of the
Sac Valley and surrounding foothills in this period.
As has been the case with recent systems, the subtropical origins
of the airmass will translate to highs snow levels which will
intitially be above Sierra passes, then eventually lower to
around 6000ft as the event winds down. Donner Summit may see a
few inches by late Monday, while ski areas could pick up 6" or
more of wet snow. Sierra ridges will see gusty southwest winds
Monday as the trough passes.
The trough pushes east of the area by Monday afternoon, ushering
in drier air and clearing skies by Monday evening. Tight north-
south pressure gradients are expected to develop on the backside
of the trough Monday night into Tuesday, creating gusty north
winds for the Valley, especially on the north and west sides of
the Sacramento Valley. -DVC
.Extended Discussion (Wednesday through Saturday)
Increasing confidence in a dry forecast for the second half of
next week as strong high pressure builds along the west coast in
the wake of the system earlier in the week as it exits through the
desert SW. Appears the main storm track will shift well to the
north of the region to along the Canadian border. Temperatures
will be unseasonably warm over NorCal under the influence of the
ridge, and breezy northerly winds will taper off as pressure
gradients relax by the end of the week.
VFR conds ovr Intr NorCal nxt 24 hrs exc areas MVFR conds in -RA
dvlpg omtns N of KRDD aft 06Z Sun. Lcl NE-E sfc wnd gsts up to 30
kts ovr nrn Siernev with isold stgr gsts ovr hyr rdgs til 18Z.