Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 201533
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
833 AM PDT Sat Sep 20 2014

.Synopsis...
Lingering Sierra showers/t-storms are possible through the
weekend, otherwise, dry & warmer temperatures into early next
week. Cooler and wetter weather arrives middle of next week into
next weekend.

&&

.Discussion...
Satellite imagery shows a cut off 578dm closed low centered just
west of the Channel Islands near Oxnard. This closed circulation
center is sitting directly under the apex of a ridge covering most
of the western US. Water vapor imagery indicates cloud enhancement
is presently occurring over the Motherlode and west slope of Sierra
Nevada this morning. Due to this and other subtle discrepancies, we
have decided to increase coverage and probability of precipitation
throughout the next 12 hours and sent out an update. Near term
model guidance is fairly consistent in bringing in showers/thunderstorms
above 4000 feet in the Sierra. Unfortunately, the HRRR model,
which has quickly become an office favorite for short term
guidance is currently unavailable. The NAM12 model has been
overforecasting convection over the last week, so we are throwing
out that model as it again appears to be overforecasting
the weekends convection. We will continue to keep a close watch on
the development of any convection in the northeastern sector of the
closed low and send out updates as necessary. DRP

.Previous Discussion...
A closed low is currently straddling the central CA coastline. It
will linger over our region today and gradually move northeastward
by tonight. On Sunday, the low will be centered over Nevada with
the backside of the low still impacting the Sierra. Have kept
mention of showers and thunderstorms over the Sierra this weekend.
The WRF model indicates that there will be more showers on the
western side of the crest Sunday. The rest of our CWA will remain
dry with near to above normal temperatures through Tuesday.
Daytime highs will generally be at their warmest today compared to
the rest of the upcoming 7 days. For the short term forecast, max
temperatures will range mid 80s to upper 90s across the valley.

Smoke from the King Fire will continue to impact the Sierra and
foothills into the adjacent Southern Sacramento valley. Hazy
conditions surrounding the smoky area will extend from the
Central Sacramento valley into the Northern San Joaquin valley. On
Sunday, general wind pattern will transition to a weak onshore
flow which should push smoky/hazy conditions eastward.

Short wave ridging behind the closed upper low moves over NorCal
Sunday into Monday for dry weather. Temperatures trend down slightly
over the weekend but remain near to a little above normal into
Monday.  JBB


.Extended Discussion (Wednesday through Saturday)

Models remain in good agreement that a stronger trough will
impact the region from Wednesday into the weekend. On Wednesday,
max temperatures will finally dip below normal. In addition, the
chance for showers will start impacting the NorCal coastline
Wednesday morning. Showers should spread over the Coastal range
and nudge into the Sacramento valley by Wednesday afternoon/evening.
The chance of showers will continue to spread eastward and
southward encompassing the majority of our CWA Thursday and
Friday. Daytime highs will be well below normal Thursday into
Saturday ranging 5 to 15 degrees below average. The one
discrepancy to watch in the models is that the GFS is more
progressive in moving the trough eastward out of our region on
Saturday while the ECMWF model has the trough still lingering.
Have kept mention of showers on Saturday, but started to diminish
them across the valley by Saturday night. JBB

&&

.Aviation...

VFR conditions the next 24 hours all TAF sites. MVFR visibility in
smoke possible in the vicinity of the King Fire. Isolated TS also
possible along the higher Sierra 18z today through 06Z Sunday.
North to east winds to 10 knots this morning transitioning to
southerly this afternoon and tonight.

&&

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

$$






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