Weather Service Report


477 
FXUS66 KSTO 221211
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
411 AM PST Wed Feb 22 2017

.Synopsis...
Significant flooding concerns continue as runoff from the recent 
rain continues to work its way downstream adding stress to 
waterways. Scattered showers with a few thunderstorms today, then
another storm potentially late in the weekend.

&&

.Discussion...
Short-wave moving thru early this morning popped a few showers and
one thunderstorm in the valley north of Chico while continuing
numerous showers over the west slopes of the northern Sierra
Nevada. Expect remaining showers will taper off this morning as 
the wave progresses to the east. Otherwise, partly to mostly
cloudy skies cover the region and temperatures are running about
5-15 degrees cooler compared to 24 hours ago.

Next upstream vort is pivoting thru 35N/130W and will approach
NorCal by this afternoon. The result is expected to be another
upswing in shower and thunderstorm activity that will last into
this evening. Small hail is expected to be the primary threat from
any stronger storms that develop.

A few showers may linger over the mountains on Thursday, but for
the most part expect dry weather to return for late-week. The
airmass will be cold, and with less cloud cover nighttime
temperatures will be quite chilly with some patches of frost
possible in the Central Valley.

Next system approaches late Friday and slowly works its way inland
on Saturday with QPF forecast to gradually increase Saturday
night.

&&

.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)
Models in fair agreement in dropping an upper low southeastward 
across Norcal on Sunday. At this time main frontal passage timing 
looks like Sunday night or early Monday and that this will be a 
fairly moderate system compared with recent storms. Snow levels 
also look relatively low so hopefully this system will not add 
significantly to current flood issues. Showers continue on Monday 
as the trough axis shifts into the Great Basin. Current 
projections put some light snow possible down into the foothills 
on Monday. Northerly flow develops on Tuesday so should see drying
most areas but Sierra still under cyclonic flow so could see some
minor continued shower activity there. Upper level ridging 
finally brings drying CWA wide by next Wednesday with this dry 
period possibly lasting for several days. Forecast highs for 
Wednesday come in right around normal for this time of year. 

&&

.AVIATION...
Scattered showers today with isolated thunderstorms this 
afternoon as upper low moves across the region. Mainly VFR 
occasional MVFR in showers. Mainly south to west winds to 15 
knots. Snow levels around 3000 feet lowering to 2000 to 2500 feet 
by Thursday morning. 

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Saturday morning for Carquinez Strait 
and Delta.

&&

$$

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Western Regional Climate Center, wrcc@dri.edu