I want to share a resource that I have been enjoying for a bit now.
It is a twice weekly weather report from the weathercafe yahoo group. It is written by *Rufus* and he seems to have a really good handle on long range weather forecasts. The group description - "The Weather Cafe provides informative long-range forecasts for specific patrons from the PNW". He has an eye out for agriculture folks.
Rufus sends out emails on Mondays and Fridays but occasionally will send out mid-week updates if there is something important to share. I got one of those today so I am passing it on....
Wednesday December 2
ARCTIC AIR MASS is poised to drop in for a visit this weekend. Western valleys may see a few snow showers as the cold front passes late Friday, with another colder shot of air due in Sunday/Monday.
A VERY COLD high pressure 'dome' of air, with surface readings around 1050 mb, will move out of the Yukon into western Canada, then nudge southeast into the U.S. heartland over the weekend. This type of pattern typically results in some of our coldest winter weather across the PNW. The heavy air mass will push rapidly out of the Fraser Valley and Columbia River Gorge into west side locations. WINDY - with wind chill factors for some patrons on the east side in the single digits. Bundle up.
This morning's lows in the mid-to-upper 20s west of Cascades (first 'hard frost' of the fall for many) is only the teaser for temps in the mid-teens probable in west side locations Monday and Tuesday mornings. Eastern basins will not get above freezing for three or four days; lows approaching zero for some.
-> Business and residential plumbing should be prepped for sub-freezing temperatures. Ranchers plan water availability for livestock.
Now, the transition. Long time residents of the PNW know that heavy, cold air 'bottles up' on the east side of the Cascades and pushes through to the west to set up some of our classic snow conditions as a warm front approaches from the west / southwest. It takes decent southerly winds to move aside the cold air mass. Come mid-week, a strong storm (remnants of T.S. NIDA) is modeled to aim primarily at California (heavy rain likely there). As the system approaches, it is very likely for SNOW at all west side locations - at least until the system stirs in warmer surface air. Could be a significant amount of snow beforehand if the center of the storm tracks in a more southern pattern.
Snow should transition to RAIN for western valleys and even some lower elevations of eastern OR / WA by sometime Thursday. This will be a WINDY storm, esp for southern OR / northern CA. Possibility for a second and third low to form moving warmer air and moderate RAIN to many PNW locations as next weekend approaches. FLOOD issues could be in play for northern CA. -> NOTE: the last of the series of fronts is likely to pull down COLD AIR on the back side, as another shot of Arctic air moves close to the WA / B.C. border next weekend. Some model runs indicate VERY LOW snow levels probable in the Dec 11 - 12 time frame, maybe even to the surface. Mountain passes will get hammered.
Your WxCafe (TM) will update this ever adjusting scenario on Friday. In the mean time, take the time to prepare for significant winter weather.