398 FXUS66 KPQR 032248 AFDPQR Area Forecast Discussion National Weather Service Portland OR 247 PM PST Fri Mar 3 2017 .SYNOPSIS...A Cold front offshore continues to slowly across the region this evening. Then much cooler with snow levels lowering. Low pres will sit offshore this weekend, maintain cool and showery pattern that will last into early next week. Accumulating snow levels will bounce between 1000 and 1500 ft this weekend into Mon, but could be as low as 500 ft later Sun night into Mon. Will see moderating temperatures next week, but rather wet weather continues. && .SHORT TERM...Tonight through Monday...Rain spreading across region this afternoon as cold front approaches. Still looks like the front will push to the coast around 4 pm, and across the interior lowlands between 6 and 8 pm. Snow levels still at 3500 to 5000 ft, but these will drop quickly overnight, settling around 2000 to 2500 feet by Sat am. Current snow advisories for the Cascades look okay, with generally 4 to 9 inches of snow tonight. May be borderline if can reach those accumulations, as moisture may be waning as the colder air arrives. But, will leave as is for now. Classic early spring pattern for the region this weekend, as broad area low pressure sits off the coast, while cool unstable air mass sits over the region. This will maintain cool showery weather for this weekend into early next week, with snow level between 1000 and 1500 feet. With such low freezing levels, will see small hail in the showers on Sat. Have the threat of thunderstorms for the coastal areas for Sat and Sat evening, but have extended farther inland across the interior lowlands to the Cascades foothills. With snow levels running at 1500 to 2000 feet on Sat, and 1000 to 1500 feet Sat night into Sunday. With showers, this would bring new snow of 2 to 5 inches over the Coast Range, Willapa Hills, and 4 to 7 inches for Cascades and foothills. These accumulations would be for each 12-hour period of Sat, Sat night and Sun. Should be enough to support a prolonged Snow Advisory criteria for those areas at that time, but may be a bit too early to issue such. Will wait for tonight's snow advisory to expire before issuing new advisories. Snow showers will get energized again later Sunday as another upper disturbance rotates around the low and into the Pac NW. But air mass cools further Sunday night, with snow level lowering to 500 to 800 feet, possibly lower. Snow will continue to accumulate on the higher elevations, there is low to moderate potential that could see minor accumulations, generally under an inch, down as low as sea level at that time. Again, this could change, as models are still in some flux. But is not out of the question. Showers continue on Monday, but snow levels will slowly rise, likely back to 1500 to 2000 feet by late in the day. Any low elevation snow that does fall will be gone by afternoon. rockey. .LONG TERM...Monday night through Friday...In the wake of the cool low from Monday, the next system will be approaching from the southwest Monday night and spreading a warm front over northwest Oregon and southwest Washington with slowly rising snow levels. The models show a decent low moving into southern B.C. and northwest Washington Tuesday as the main cold front moves into our forecast area. This front will tend to remain in our area Wednesday as another disturbance moves through. The models show another decent front moving through around Thursday. Snow levels will be rising to near Cascade pass elevations Tuesday and remain near or just above pass elevations during the mid week period. Model consensus is less late in the week with the GFS and Canadian models suggesting another cooler air mass spreading in with significantly lower snow levels late next week, while the latest ECMWF model has snow levels very high as the air mass dries out. This is even a significant departure from the ECMWF's previous run, and for now looks to be an outlier. Will keep the current forecast closer to the GFS and Canadian for now. All in all, this looks like an active wet week, with the potential for fairly heavy rain Monday night and Tuesday and again around Thursday. Tolleson && .AVIATION...The cold front will continue to bring periods of steady rain this afternoon as it moves across the forecast area. Expect predominately MVFR conditions through this evening, with localized IFR conditions under heavier rain bands, mainly along the coast. As the front moves across the interior this afternoon expect periods of gusty southerly winds to 30 kt. Steady rain will taper off later this evening, with conditions becoming showery under primarily VFR conditions inland and MVFR conditions along the coast. Expect the higher terrain to remain obscured tonight and Sat. An unstable air mass moving over the area will bring a slight chance of thunderstorms to the forecast area Sat. KPDX AND APPROACHES...Expect conditions to become predominately MVFR under light rain as the cold front move across the terminal this afternoon. Gusty southerly winds to 30 kt will continue through around 02Z. Conditions will become showery and trend towards VFR after 03Z this evening. An unstable air mass will bring a threat for thunderstorms Sat. /64 && .MARINE...The cold front will continue to move across the coastal waters this afternoon, with gusty southerly winds likely through late this evening. Models continue to show a weak coastal jet developing for a few hours this afternoon, with occasional gusts to 40 kt. However, expect any gale gusts that develop to be brief and localized, with most areas generally seeing gusts to 30 kt so will stick with the current Small Craft Advisory. Gusty southerly winds, combined with a background westerly swell, will keep seas up around 10 to 12 ft through later this evening. Seas look to briefly subside below advisory criteria tonight. Low pres near Haida Gwaii will continue to drop SE tonight and linger over the coastal waters this weekend. A cold and unstable air mass will keep showers going this weekend, with a threat of thunderstorms Sat and Sun. Things become a little more uncertain early next week. However, models continue to show the potential for a series of low pres systems to develop over the NE Pac and impact the coast waters. As such, we could see a period of gale gusts develop late Mon/Tue with seas building into the mid teens but confidence is low. /64 && .PQR WATCHES/WARNINGS/ADVISORIES... OR...Winter Weather Advisory until 6 AM PST Saturday for Northern Oregon Cascades. Winter Weather Advisory from 6 PM this evening to 6 AM PST Saturday for Cascades in Lane County. WA...Winter Weather Advisory until 6 AM PST Saturday for South Washington Cascades. PZ...Small Craft Advisory for winds and hazardous seas until 10 PM PST this evening for Coastal Waters from Cape Shoalwater WA to Florence OR out 60 nm. Small Craft Advisory for Rough Columbia River Bar from 6 PM this evening to midnight PST tonight. Small Craft Advisory for Rough Columbia River Bar from 6 AM to noon PST Saturday. && $$ Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland This discussion is for Northwest Oregon and Southwest Washington from the Cascade crest to 60 nautical miles offshore. The area is commonly referred to as the forecast area.