Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 091700
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
1000 AM PDT Sun Mar 9 2014
A stream of Pacific moisture will bring precipitation to the
region today and early Monday, especially for areas north of I-80.
Breezy winds are possible Tuesday. Dry and mild conditions return
for the remainder of the week.
.SHORT TERM DISCUSSION...
Satellite Blended Total PW shows about a 1.3+" (or 160-190% or
normal) TPW plume from the vicinity of HI NEwd onto the Nrn CA
coast. IR imagery shows a rather disorganized cloud band this
morning along the frontal band as WAA precip develops out ahead of
the frontal band over the NWrn portion of our CWA. This will be the
case for much of the day today...until large scale ascent from the
upper trof west of 130W begins to interact with the moisture plume
and frontal band as it moves Ewd later today and tonight. The
current cloud enhancement W of 130W and south of 40N is what we
should be seeing develop on our doorstep late today and tonight. In
the meantime...snow levels will be very high in the WAA zone
today...with the snow profilers this morning showing above 9 kft.
Upper trof along 140W is forecast to progress Ewd to near 130W by
00z Mon...and across our CWA between 12z Mon and 21z Mon preceded by
the cold front that is forecast to move across our CWA from 03z Mon
to 18z Mon. We should see an uptick in precip rates with the frontal
band within a couple of hours of the 06z-12z Mon time frame. A
higher probability of convection is expected with the frontal
band...with the possibility of post frontal convection into Mon
morning over the Srn Sac/Nrn San Jqn Vly. Jet dynamics could also be
a factor as the timing of the frontal band is also forecast to be
nearly coincidental with the timing of the upper jet over our CWA.
The initial surge of drier air behind the upper trof axis will
augment instability in the forenoon hrs...but will gradually
increase stability from west to east during the afternoon.
Cyclonic flow transitions to anticyclonic on Tue. Pressure/height
rises will tighten the Nly and NEly pressure gradients on the
backside of the trough Mon nite into Tue creating gusty north winds
for the N and W sides of the Sac Valley.
Due to the subtropical origin of the TPW plume...snow levels will be
high above the Sierra passes and then lower behind the cold front to
around 5500 to 6000 ft...but by then the plume would be shunted Swd.
2-6 inches expected over the high Sierra with up to 10 inches over
the higher peaks. QPFS from 1 to over 2.5 inches are expected over
the mtns...with amounts near an inch in the Nrn Sac Vly tapering to
.10 to .25 over the Srn Sac/Nrn San Joaquin Vly.
Retrogression of the Great Basin trof/upper low becoming a little
more prevalent in later model runs. This may result in breezy/windy
conditions over the Sierra Crest south of I-80 on Wed. Temps
expected to warm under the katabatic wind regime. JHM
.Extended Discussion (Thursday through Sunday)
Increasing confidence that high pressure will strengthen across
the region later this week and next weekend. This will result in
dry weather with very mild temperatures for the interior of
NorCal. Look for Central Valley highs to warm through the 70s into
the lower 80s by the weekend with mountain readings warming from
the 50s and 60s into the 60s and 70s.
Frontal system remains nearly stationary over far northern
California. Generally VFR conditions expected across the Valley the
next 24 hours, with -SHRA remaining mainly north of KCIC through
about 06z Monday then shifting southward through Sacramento.
IFR/LIFR conditions likely to develop over higher terrain tonight.
Winds will generally remain below 10 kt across the Valley.
Southwest wind gusts up to 30 kt possible over higher terrain.