Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 062244

Area Forecast Discussion
National Weather Service Sacramento CA
244 PM PST Wed Dec 6 2017

Dry weather this week with cool nights and mild days.


Very strong blocking pattern has set-up over the Ern Pac/NOAM with a
persistent strong ridge locked in place over Wrn NOAM by two deep
lows/trofs, one over Hudson Bay/James Bay and the other over the
Gulf of AK. Models continue this blocking pattern through all of
next week with the 06/06z GFS suggesting there may be some
undercutting of the ridge around/by Dec 18th or 19th. In addition,
the GFS, and even more so the ECMWF, suggest a weak/moderate
"inside slider" may weaken the ridge around the 14th/15th which
would bring some cooling and windy conditions to the Sierra, if
this materializes.

Thus, more of the same type of wx for Norcal with mild daytime
temperatures, about 5 to 13 degrees above normal, and cool/chilly
nights with clear skies resulting in strong radiational cooling
into the weekend. The formation of the radiative inversion should
cause winds to diminish in the valley and lows will generally be
in the 30s with patchy frost possible the next couple of nights,
especially in outlying areas. The exception is in the Nrn Sac Vly
tonite as brisk Nly winds gradually decrease but maintain some
mixing overnite. Winds should diminish Fri/Sat as the high
pressure center repositions inland and over our CWA.   JHM



A ridge of high pressure centered over the western U.S. will keep
the forecast area under stable conditions through the extended
period. In addition, daytime highs will run up to 10 degrees
above seasonal normals. Light northerly winds will limit fog
development in the area, though some overnight mist and morning
haze are possible at times.



General VFR conditions expected at the TAF sites, though local
MVFR visibility is possible for the northern San Joaquin Valley
after 12z Thursday. Light winds except for gusts up to 20 kt over
the northern Sacramento Valley through 03z Thursday.



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