Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 261012
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
312 AM PDT Fri May 26 2017


.SYNOPSIS...
Temperatures level off Friday with near to below normal
temperatures. Slow warming trend this weekend into early next
week. Isolated afternoon showers or thunderstorms possible over
the northern Sierra into early next week.

&&

.Discussion...
Upper low over the northern Great Basin with upper trough dropping
slowly southward across the north state. This trough is bringing a
few clouds to the northern CWA but bigger influence is a continued
very deep marine layer. Fort Ord profiler is showing a marine
layer depth of nearly 4000 feet. Although deeper than 24 hours
ago...believe coastal stratus intrusion into the central valley
will be more scattered this morning as stratus layer becomes more
dispersed. Although most locations will see similar high
temperatures today...delta influenced areas may see a little
warming thanks to a weaker delta breeze today. GFS paints a small
area of precipitation over the northern Sierra this afternoon as
upper trough axis moves through this region so left a slight
threat of thunderstorms northern Sierra crest for the afternoon
and evening hours even though other models to not have this
feature. Upper ridge pushes in over the west coast on Saturday
bringing the beginning of a warming trend. Marine layer will
likely be squashed down significantly so morning marine stratus
intrusion will likely be minimal. GFS and NAM both paint light
precipitation over the northern Sierra associated with upper
trough axis. Upper ridge shifts inland on Sunday bringing a bit
more airmass warming. Daytime highs will reach from a few to
several degrees above normal. GFS and ECMWF models add light
precipitation to the northern coast range Sunday afternoon as a
shortwave ripples northward across the northwest corner of the
state. Since timing on this feature could change...will wait for
more model runs and consistency before adding any precipitation
threat here. Airmass warms a bit more on Monday as upper ridge
amplifies over the west. Southerly flow aloft could bring moisture
farther up the Sierra so may see a better chance of Sierra
thunderstorms going into the early part of next week.

&&
.EXTENDED DISCUSSION (Tuesday THROUGH Friday)

Ridging shifts east on Tuesday in advance of upper level trough
approaching the West Coast. One more warm day in store for Tuesday
though latest model guidance has actually trended cooler and have
nudged max T`s down accordingly. Highs will top out in the upper
90s across the northern Sac Valley, low 90s elsewhere in the
Valley and 60s-70s in the mountains. Trough moves into the area on
Wednesday and lingers across the region into Thursday. 00z GFS
showing more robust system with higher moisture return, painting a
chance for showers and thunderstorms across the mountains and
possibly even across the Valley. ECMWF features drier solution
with little to no precipitation as the trough moves through. For
now, have hedged toward a blend with slight chance POPs across the
mountains. Regardless of precipitation chances, cooler
temperatures will return for Wednesday and Thursday with more
seasonable highs. Delta Breeze should be kicking again as well.

CEO

&&

.AVIATION...

Stratus intrusion possible from the Delta into the central Valley
this morning, causing brief period of MVFR cigs at Sacramento TAF
sites. Otherwise VFR conditions through the period. Winds
generally 10 kts or less for TAF sites with gusts to around 20 kts
invof the Delta.


&&

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

$$



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