Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 011917
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1117 AM PST Wed Mar 1 2017


.Synopsis...
Flooding concerns continue as runoff from recent rain continues
to work its way downstream adding stress to waterways. Dry
weather with warming trend through the end of the week. Wet
pattern returns this weekend into next week.

&&

.Discussion...
Sunny skies with a cool start in some Valley locations, reaching
the low 30s in some spots, with patchy frost. Temperatures up in
the mountains started the day 5 to 10 degrees warmer than
yesterday, as upper ridging builds. Warm temperatures in the low
60s are expected in the Valley and Delta this afternoon, 50s to
around 60 in the foothills. Forecast is on track, no updates
needed.

Thursday morning lows are not expected to be quite as cool, so
will remove mention of frost.

Friday looks dry during the day, but models speeding up some in
bringing the next wet system in Friday night, with precipitation peaking
Saturday night into early Sunday. This rather cool system
originates from the Gulf of Alaska. The main concerns are some
breezy winds, and snow in the mountains. Early storm total
estimates are a foot of snow above 5000 feet, potentially 2 feet
at pass levels. With much of the precipitation in the form of
snow, runoff is expected to be limited. EK

&&
.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)

Mid range models in good agreement in swinging a Pacific cold
front through northern California early Sunday. Area of highest
precipitation appears to be over the northern Sierra where good
orographics squeeze out the most moisture. Fairly low snow levels
will make for travel impacts over the Sierra Cascade range with
several inches of snowfall currently forecast above about the 3000
to 4000 foot level. Frontal system shifts east of the state by
Sunday evening with showers likely to continue through the night
as the associated upper trough passes through the Pacific
Northwest and northern California. Model confidence decreases on
Monday as models diverge on strength of weak upper ridge over the
west coast. GEM model would indicate a fairly dry solution with a
much flatter ridge solution of the GFS bringing precipitation to
nearly the entire forecast area. Have compromised for now by
putting in light precipitation north of about interstate 80. Next
Pacific frontal system is forecast to move through around Tuesday
but model timing not showing a lot of consistency. ECMWF model
the fastest bringing this system through Norcal Tuesday afternoon
while the GEM and GFS hold off until Tuesday night and both have
weaker solutions. Snow levels are a little higher with this system
but still low enough to cause Sierra travel difficulties. Model
inconsistencies continue through the middle of next week with GFS
and GEM showing a drier ridge solution and ECMWF showing a wetter
trough solution. Have kept chance pops in for most of the CWA for
now but confidence remains low until better model consistency is
achieved. Daytime highs through the extended period remain a
little below to near normal.

&&

.AVIATION...

VFR conditions next 24 hours. Winds generally below 10 knots.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through late Thursday night for Carquinez
Strait and Delta.

&&

$$


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