WEATHER SUMMARY AND FORECAST DETAILS
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FOR 2/22/2018 -
What a busy week it has been, but we`re not finished yet with the active winter pattern. Of course this morning's snow storm got everybody's attention. The timing laid out for it's arrival in the various parts of our area was right on schedule. However, what ALL of the models and data missed out on was the very significant wave that developed on it as it came in. And in the front to middle section of that wave snowfall rates were 2 - 3 inches per hour. This accounted for so many reports from people who said they awoke to nothing, and then seemingly had 3 inches within an hour. That was likely because they did. Widespread reports of 3 - 6 inches of accumulation in the valley floors this morning have been received. Some areas with favorable downsloping off terrain saw more like 8 +. The rising snow levels today and the sun have made short work of the snow we did see this morning below 2000 feet. That 3.5 inches we got here at World Headquarters is already just a fond memory with only the remnants all that is left of the snow fort that the junior partner and her friends constructed. Yes, the Snow day was put to great use by her.
Showers have continued across the area this afternoon, with some reports of graupel and rain mixing in here and there. And as i have pointed out many times over the last 10 days, graupel / snow pellets is not hail. Round and white yes, but still not hail. Graupel forms when water droplets freeze to snowflakes. Hail is created by convective processes that we just do not have. These will gradually diminish and move off to the south by this evening, with dry air on the back side of the departing wave likely to bring us some clearing overnight. This clearing, if and when it happens, is the first concern on the docket. Where we see significant clearing tonight, temperatures are likely to drop quickly to below freezing, and inland from the coast, much cooler than that. This will be helped by any residual snow on the ground and the cold air mass in place overhead. Any snow melt on the roads or walking surfaces is likely to freeze, and this could lead to black ice, a significant concern to anyone driving or walking on said surfaces. This could be a major factor for schools in the area tomorrow morning. If we get really hazardous road surfaces as it looks like we could, do not be surprised if there are a number of school districts who opt to go with 2 hour late starts. Also, these cold temperatures will drain down to the coast and valley bottoms, leading to cold overnight lows that could have a detrimental impact on local agriculture. At the coast, where freezes are uncommon, a freeze warning has been issued for tonight. Elsewhere, since the growing season has yet to begin, there are no headlines. However, the warmer than average temperatures of the past month have lead to some early growth, and these plants and trees could see some damage or stunted development unless the proper precautions are taken.
The second concern today has been the next system arriving Friday night into Saturday. While seeming a bit more robust in the model solutions today, it is also trending a bit warmer. As the system enters the area Friday night, snow levels will begin very low, but as precipitation continues into the morning, snow levels are expected to rise to above the valley floors. The predominant flow of the system will be west to east, and this will lead to upslope lift for westerly slopes, especially along the Cascades, where the heaviest precipitation is likely to occur. A winter weather advisory has been issued for the Cascades, the Siskiyous and everything above 2000 feet in Southwestern Oregon. A Winter Storm Warning has been issued for Eastern Douglas County, where the heaviest snow amounts are expected. There is a very slight chance that some localized areas, especially in the smaller valleys of the coastal ranges, could see a brief period of freezing rain as precipitation begins or changes over, but confidence is very low. So, long story short....this next system will produce another round of significant snow at low elevations, but it is not expected for the valley floors. However, as we saw this morning, the unexpected can happen. And if we hang on to cold air longer at the surface without mixing out......well, then there is a slight chance we could be looking at another high impact snow for the valley floors down to around 1000 feet on Saturday morning.
Showers will taper off Saturday afternoon and evening, but never quite come to an end before the next wave arrives on Sunday. Snow levels will begin this event on the lower side once again, then rise throughout the day Sunday. It appears the bulk of precipitation will arrive after snow levels rise above the valley floors Sunday afternoon, but significant snow is expected in the mountains Sunday evening and night, with around a foot of new snow possible above 5000 feet for BOTH the Cascades and the Siskiyous. This by the way is the biggest reason Mt. Ashland is deciding to re open tomorrow. They knew this was coming as this storm has been well detailed for over a week now. Same with Mt. Shasta. Much easier to make the call to open knowing you are going to be getting a big shot of snow arriving. Snow levels will begin to fall heading into the late night, but precipitation is expected to lighten and transition to showers heading into Monday morning. We may, just may hold to enough moisture to get yet another possibility of snow on the valley floors for Monday morning. And then just when I thought it could not get any more interesting looking......along comes this.
The models and data had been indicating that we would be stormy and cold for next week. But, today as the data has really come into better focus......something really is grabbing attention. We are seeing atmospherics lining up that look very close to what we saw develop last year on January 3rd. The data is showing a rich moisture source coming into play. In forecaster parlance, we are looking at a moist conveyor. And then coming in over that moist conveyor are air temps that look almost identical to what we saw last January. I was wondering if I would ever see that again in my lifetime last year. And now here is that set up developing again. Can't hardly believe this! And now that I have said that.......I NEED to say this. We are still a very long way out from this happening. BUT, we do have our first indications that could be developing. I am obviously going to watch this like a hawk! Two runs of data does not an absolute make. Especially six days out. But boy is this ever going to bear watching!
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