Lots of Rain in the Forecast in the next 6-14 Days

(NWS Medford) It looks like January will start off on the wetter side. There is a high probability for a wetter than normal pattern over the next 6 to 14 days. With some colder temperatures, we’ll see the snowpack really begin to build early January. Here is the latest forecast discussion from NWS Medford: .Short Term...Tonight through Thursday Night...Satellite imagery this afternoon shows a broad area of high clouds overspreading the region, emanating from a robust low centered well offshore to our west. This is the next front to impact our forecast area, expected to move in tonight and much of tomorrow. This is just the first round of what will be an extended period of very active weather. The pattern upstream is like a loaded cannon: A deep, broad, and very cold trough is centered over Siberia/Kamchatka, with swift near zonal flow extending from Japan all the way across the Pacific to roughly 150 degrees west, between Alaska and Hawaii. Multiple waves of energy emerging from the trough will then move quickly across the Pacific, picking up moisture, and emerging from the flow aimed right at the Pacific Northwest. This pattern looks to hold fairly constant through at least the next week, with models across all suites and ensembles in nearly unanimous agreement for a wet, windy, and in some areas, snowy week ahead. This first front will approach the coastline tonight, with winds increasing there through the early morning. The exposed areas, especially headlands, should become quite gusty by sunrise. Gusty winds will spread inland through the day, especially over the higher terrain. Surface pressure gradients are strong enough to make strong winds a concern in the Shasta and southern Rogue Valleys, but the mid level winds are expected to be more southwesterly, and not well aligned with the terrain. The gradient should be enough to make for a breezy day in Ashland, with gusts in Weed likely to be strong enough for a Wind Advisory. Meanwhile, 50 to 60 kt 700 mb winds across the East Side should result in breezy valleys, along with strong winds across the ridges and in the Summer Lake and Abert Lake areas. All areas will see winds diminish once the front passes: at the coast mid afternoon, and in the Shasta Valley and the East Side by late evening. Some wind headlines are in place for the areas around Weed and for portions of the East Side, and details can be found at PDXNPWMFR. The next concern will be rain and snow, although the snow amount forecast will be tricky given the snow levels and the timing of the heaviest precipitation. Rain is expected to begin at the coast Wednesday morning, spreading inland to the Cascades by afternoon, then across the East Side in the late afternoon and evening. As precipitation starts in the Cascades and Siskiyous, snow levels should be hovering around 5000 feet, but they will fall quickly as the heaviest precipitation arrives along with the passing of the front. Across the East Side and in the areas near Mount Shasta City, snow levels will be lower, and precipitation should begin as snow, but some valleys could see a brief changeover to rain or a mix in the afternoon before snow levels drop with the arrival of the front. The bulk of the snow, around 8 to 10 inches, should fall in the Cascades, with several inches spilling into the Highway 97 corridor east of Crater and Diamond Lakes. The heaviest rates are likely in the late afternoon and early evening, right before the front arrives, but if the timing changes just a bit, and the heavier precipitation arrives before snow levels can drop, then snow amounts could trend lower than expected. Winter Weather Advisories remain in effect for these areas, and details can be found at PDXWSWMFR. The majority of the precipitation should end Wednesday night, but post-frontal showers will linger well into Thursday morning, primarily along the western slopes of the coastal mountains and the Cascades, where upslope flow will be strongest. Some light precipitation, mainly drizzle, is then possible Thursday evening along the coast and into the coastal ranges as a weak warm front moves onshore, just ahead of the next cold front lying just offshore. -BPN .Long Term...Friday through Tuesday...An active weather pattern continues in the extended, bringing multiple storms and snow levels low enough to continue to impact mountain passes. It does look like there are at least small breaks between each system, so there doesn`t appear to be a long-lasting Atmospheric River event among the bunch. Rivers will continue to rise but based on current data and forecasts, no mainstem rivers are expected to reach bankfull through Tuesday. A front will approach the forecast area on Friday, and winds will increase from the southwest during the day. The front pushes through quickly late Friday and will bring a half inch to inch of precipitation to the coast, a quarter inch to West Side valleys, half inch in Western Siskiyou County, and about a tenth of an inch at Mount Shasta City. Precipitation amounts drop off quickly east of the Cascades with this system. Snow levels with the Friday front will likely be higher than the rest of the fronts in the extended, at about 5500 feet. A wetter front arrives late Saturday, and this packs more of everything compared to the Friday system. Surface pressure gradients are expected to be -6 to -8 mb between Medford and Redding and -8 to -12 mb between North Bend and Arcata. These magnitudes are significant and could bring high winds to areas like the coast, Shasta Valley, and east of the Cascades. Upper level winds are strong as well, with the GEFS mean wind at 10000 feet 50kt. We maintain hefty winds in the forecast for this event, even though it`s almost 5 days out. Turning to precipitation, Integrated Vapor Transport (IVT), a good measure of how much moisture is pointed at our region, is forecast to be in the top 10 percent for this time of year. This is especially significant considering we`re around the wettest time of year now. Snow levels are expected to be around 5000 feet at the onset of precipitation, lowering to around 4000 feet behind the front. Periods of heavy rain are expected Saturday night and Sunday morning, and rivers and streams are expected to rise. Showers diminish late Sunday behind the front, and after that point, confidence in the forecasts decreases some. Taking a look at the various ensemble solutions from the Canadian, American, and European models, another strong front could arrive Monday or energy could just ride to the south of the CA/OR border, bringing lighter precipitation amounts/wind. The forecast maintains 40 to 70 percent chances of precipitation on Monday into Tuesday to account for the wet model solutions, which account for the majority. Snow levels dip to their lowest elevations over the past week, at about 3000 feet by Tuesday. -Keene