307
FXUS66 KSTO 150930
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
230 AM PDT Sun Sep 15 2024

.Synopsis...
Cooler and more unsettled weather thru mid-week with a chance of
showers and thunderstorms. Dry and warmer weather returns late in
the week.

&&

.Discussion...
Clouds and a few light showers are beginning to work their way
southward into far northern California along the front early this
morning. To the south ahead of the front, skies remain clear with
relatively mild temperatures (readings in the mid 60s to mid 70s
through much of the Central Valley outside of areas influenced by
the Delta Breeze).

Northwest California will continue to see the best chance for
showers today as short-wave energy digs the trough southward
offshore. The HREF shows the best potential for showers and
thunderstorms over northern portions of the Coast Range up into
Shasta County later today as moisture and instability pool over
the north end of the valley ahead of the trough. Later tonight and
Monday, shower potential is likely to spread south and east over
the remainder of the forecast area with the upper low, also
bringing potential for a little snow over the higher elevations of
the northern Sierra (recent warm weather may alleviate potential
for much accumulation on road surfaces).

QPF is generally expected to remain under 0.25" with some mountain
areas possibly seeing up to 0.50" (locally higher with
thunderstorms in the Coast Range and Shasta County).

Later Monday into Tuesday we`ll likely see a brief break in
showers before another system drops down from the north on
Wednesday bringing renewed shower and thunderstorm chances.

Temperatures will also be considerably cooler through mid-week
with readings expected to be around 10-20 degrees cooler compared
to Saturday`s highs.

&&

.EXTENDED DISCUSSION (Thursday THROUGH Sunday)...
Models differ with progression of upper low through CA Thursday
with NBM leaning more towards slower EC. As a result, threat of
showers advertised to continue over the Sierra Nevada Thursday.
Expect mainly liquid precip as snow levels climb above 10k ft by
Thursday afternoon. AMS warms Thursday as upstream EPAC upper
ridging begins to build inland. Highs forecast in the low to mid
80s in the Central Valley with highs in the mountains and
foothills ranging from the upper 40s at the highest elevations to
70s in the foothills. Some locally gusty northerly wind possible
Thursday as stronger winds aloft mix to the surface. Warming trend
continues into the weekend as heights trend up. Highs expected to
be near to slightly above normal by Sunday.

&&

.AVIATION...
VFR conditions through abt 18z, then areas of MVFR/IFR spread
from N to S across interior NorCal thru 12z Mon, mainly from I-80
northward and over the mtns. Isolated tstms possible N of I-80 aft
21z. In Central Vly, areas of Sly sfc wind up to 15 kts. Vcnty of
Delta, SWly sfc wind 15-25 kts with local gusts to 35 kts. Over
hyr trrn, areas of SWly sfc wind gusts 30-40 kts.

&&

.STO WATCHES/WARNINGS/ADVISORIES...None.

&&

$$