December 6, 2017 – Dry weather this week with cool nights and mild days.
Discussion
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 19 Dec. In addition, the GFS suggests a weak “inside slider” may weaken the ridge around the 15th.
Thus, we will have more of the same type of weather with mild daytime temperatures a few degrees above normal, and cool/chilly nights with clear skies resulting in strong radiational cooling. 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.
Extended discussion (Sunday through Wednesday)
Strong ridging will keep dry weather and above normal temperatures over the area into early next week. This blocking ridge will effectively divert any systems well to the north into British Columbia. Light northerly winds will limit fog development in the area, though some overnight mist and morning haze are possible at times.