Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 171043
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
343 AM PDT Wed Sep 17 2014

.Synopsis...
Temperatures cooling to below normal Thursday with a chance of
showers and thunderstorms. Warmer and drier weather returns for
the weekend.

&&

.Discussion...
Upper trough axis between 130-140W early this morning. Most of the
region is seeing some mid and high clouds ahead of the trough,
though the far southern portion of the forecast area remains
clear. The marine layer remains quite shallow and onshore
gradients are weak.For the most part, temperatures are a little
warmer than 24 hours ago with the increase in clouds and range
from the 50s in the cooler mountain valleys to the 60s in the
Central Valley.

The trough will continue to approach the region today, however it
looks like precip chances inland will likely hold off until
tonight. We`ll see a mix of clouds and sun today. Temperatures
will likely cool a bit further and winds will increase.

The bigger changes will hold off until later tonight and early
Thursday as the trough nears the coast and a weakening frontal
system moves onshore. Scattered showers can be expected across the
region Thursday along with a chance of thunderstorms in the
afternoon as the cooler air aloft moves overhead. Despite pretty
impressive TPW approaching 1.5 inches, overall QPF is forecast to
be light given the rather weak nature of the system. Some areas
may see a 1/4 inch or so, but most of interior NorCal will likely
see less than a tenth of an inch. The cooler airmass along with
the clouds and showers will result in considerably cooler
temperatures on Thursday.

System forecast to close off and drops south to off the SoCal
coast Friday and Saturday before lifting out to our east across
the Great Basin on Sunday. The eastern fringes of the forecast
area may see some clouds and a slight chance of showers and
thunderstorms, but the remainder of the region will warm up and
dry out.

Some considerable model differences develop next week with over
200m height differences forecast at 500 mb in the latest
operational runs over NorCal depending on which model you look at.
With ensemble means still favoring a ridge, will continue the dry
and warm/hot forecast for now.

&&

.Aviation...
Mainly VFR conditions next 24 hours with isolated showers/
thunderstorms possible over western Shasta County and Coastal
range beginning this afternoon and spreading SE over valley and
into Sierra by tonight. Local SWerly surface wind gusts up to 35
to 45 kts possible over higher mountain peaks this afn/eve and
overnight. SWerly gusts up to 20-25 kts through delta and Sac
Valley this afternoon.

&&

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

&&

$$




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