Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 130442
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
940 PM PDT Fri Sep 12 2014

.Synopsis...
Dry with high temperatures 6 to 12 degrees above normal through
the weekend, cooling to near normal for next week.

&&

.Discussion...
Max temps on Fri were slightly warmer than Thu...up to 5 degrees...
over most of the CWA except for slight cooling in the mountains
including the coastal range. A weak short wave is moving Ewd into
the ridge along the W coast and spreading lines or patches of cirrus
nothus/uncinus across Norcal. NWS speed tracker shows an Ewd
movement of 20 kts with the back edge of the clouds reaching the
coast between 15z-16z Sat. By Sat afternoon...these clouds should
be clearing interior Norcal. Some minor cooling up to 4 degrees is
expected over interior Norcal on Sat as the ridge weakens slightly
and onshore gradients also strengthen slightly. Still a warm/hot day
with max temps some 10 degrees or so above normal.  JHM

.Previous Discussion...
The flow aloft will back from the northwest to the southwest as the
Eastern Pacific ridge shifts onshore as a result of a closed low
near 140W kicking the ridge from its flank. Weak onshore flow will
replace the weak offshore flow this weekend. Highs at or just below
100 degrees tomorrow throughout much of the valley. Temperatures
will gradually cool over the next week as the pattern shifts away
from subsidence and offshore flow. Dry conditions continue with near
normal temperatures into early next week.

&&


.Extended Discussion (Tuesday through Friday)

Medium range models showing omega pattern progressing early next
week with upper ridging moving into the Intermountain West as
upstream troughing approaches the West Coast. Main impact will be
increased onshore flow and synoptic cooling. As a result, max
temperatures expected to return to near normal by midweek. Models
move embedded short wave in trailing trough of omega pattern
through Interior NorCal Wednesday followed by a weaker one
Thursday, that takes a more northern track. Progs showing limited
moisture over NorCal with these waves, and latest runs keep deeper
tropical moisture south of the CWA. So for now will continue a dry
forecast, but acknowledge that future runs could bring more remnant
moisture from Odile farther north. Models differ with rate of
progression of omega pattern as ECMWF-HiRes/GEM tending to keep
some baggy upper troughing over the area next Friday. GFS moves
feature farther downstream and begins building EPAC ridging
inland. Temperature guidance suggest the latter solution, with
temps warming to slightly above normal at the end of the week.

&&

.Aviation...

Upr rdg ovr NorCal with dry Wly flow alf. VFR conds ovr Intr NorCal
nxt 24 hrs with SCT-BKN cirrus over rtes through 19z-20z Sat...then
clearing. Sfc wnds genly lgt exc isold Wly sfc wnd gsts to 25 kts
poss ovr hyr mtn trrn aftns into eves.

&&

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

$$





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