Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 172142
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
242 PM PDT Sun Aug 17 2014

.Synopsis...
Temperatures will be near to a few degrees below normal
through the week. A low off the CA coast may bring some isolated
showers/thunderstorms for mainly the Coastal Range and Shasta
County on Monday and Shasta County and Lassen Park area on Tuesday
and over the Sierra mainly south of Lake Tahoe on Tuesday and Wednesday.

.Discussion...
Weak shortwave over the area and a low dropping along the coast
of Washington today. Low clouds inland to Cordelia this morning
dissipated around 11 am but should return again the next couple
mornings. Temperatures this afternoon are running similar to a
little cooler than yesterday afternoon with temperatures in the
mid 80s to mid 90s in the Valley and 70s and 80s in the mountains.
Maximum Temperatures today are expected to be in the 90s in the
Valley and 70s and 80s in the mountains, which is near to a little
above normal for mid August. Cumulus clouds starting to develop
with the instability north of Shasta County this afternoon so we
should be dry today.

The low that is off the coast of Washington today will glide down
to the Northern California coast by tomorrow afternoon. This will
bring some instability and moisture over the Coastal Range and Shasta
County for a slight chance of thunderstorms. Although, the best
instability will still be north of Shasta County. Temperatures
will be similar to a little cooler on Monday with stronger onshore flow
and deeper marine layer with low along the coast. The low continues to
drop down the California coast on Tuesday to around Pt Conception
with a broad trough over California. A little instability and
moisture over the Shasta County and the Lassen Park area and down
the Sierra...mainly south of highway 50 Tuesday afternoon for a
slight chance of thunderstorms. The best instability will be to
the north and east of the area. Temperatures on Tuesday and
Wednesday are expected to stay near normal for this time of year. The
low moves farther south and east on Wednesday but there is
variability in its track in the models. If the low is farther
north and inland like the NAM we could get some instability and
moisture wrapping around into the Sierra south of Highway 50 so
added a slight chance of showers and thunderstorms for Wednesday
afternoon.


.Extended Discussion (Thursday through Sunday)

Medium-range models continue to struggle with the evolution of the
cutoff low beyond Wednesday. The GFS weakens the system and
eventually phases it in with a Pacific Northwest trough late this
week. The ECMWF and GEM keep the low stronger off the Baja
California coast, and eventually retrograde it westward as high
pressure builds over the Desert Southwest. Both solutions are dry
for Northern California, but the EC and GEM would be substantially
warmer than what the GFS shows. Our forecast is a blend of the
two very different solutions, with hopes of improving model
consensus soon.

Dang


&&

.Aviation...

VFR conditions the next 24 hours across interior Northern
California, except local IFR conditions west of KSUU tonight into
early Monday. Winds will remain below 15 kt across Valley TAF
sites, with local SW winds 10-20 kt near the Delta and over higher
elevations.

Dang


&&

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

$$






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