804 FXUS66 KPQR 130421 AAA AFDPQR Area Forecast Discussion...UPDATED National Weather Service Portland OR 815 PM PST Sat Mar 12 2022 UPDATE for evening aviation weather and upcoming 06Z TAFs... .SYNOPSIS...A strong frontal system will move through the forecast area tonight. This will bring very windy conditions to the beaches and headlands, breezy to windy conditions inland and significant snowfall to the Cascades. A weak atmospheric river pattern is expected to spread over the region Monday and exit by Tuesday afternoon. Additional weaker systems the remainder of next week will maintain cool and somewhat unsettled conditions over the area. && .SHORT TERM...TONIGHT THROUGH TUESDAY...Early afternoon GOES water vapor imagery revealed a rapidly developing surface low pressure area near 46N 133W. Strong development was also noted just to the south indicated by an area of dry air aloft associated with a jet maxima. At 21Z KRTX doppler radar showed the leading edge of the incoming precipitation shield along the coast. Strong pre-frontal south wind has already developed along the coast. KONP recorded 40-45 mph gusts since 18Z. The 3-hr NAM surface pressure forecast valid 21Z suggested a central low pressure of 988 mb. Buoy 46005 reported 990.4 mb at 20Z. Models have come into good agreement showing the surface low making landfall near KAST around 12Z Sunday. This will mark an abrupt weather change for the forecast area. The first round of wind (already occurring at the coast early this afternoon) will persist through about 06Z Sunday. A second burst occurs late tonight into Sunday morning, associated with the bent-back occlusion. Oftentimes, wind gusts are higher with the bent-back occlusion due to strong wind aloft mixing to the surface. No changes to the wind highlights. Expecting gusts to 60 mph for the Oregon beaches and headlands. Peak gusts for the south Washington coast will be lower as the low pressure center ends up south of that area. The 12Z WRF-GFS shows peak 10 meter wind gusts of 35-40 mph in portions of the Willamette Valley between 09Z and 15Z Sunday. Cannot rule out isolated gusts to 45 mph in higher terrain. Models show the strongest valley gusts focused between KUAO and KS12. The 12Z HREF ensemble mean indicates peak 10 meter gusts for the Willamette Valley of 40-45 mph, or a little stronger than the NAM and 4km WRF-GFS. Snow levels fall below the Cascade passes by midnight. The main snowfall period will be late tonight through 18Z Sunday. Southwest to West 850 mb flow of 35-50 kt into the Cascades late tonight through 15Z Sunday will promote significant orographic enhancement. Would not be surprised if hourly snowfall rates of 1 to 1.5 inches occur in the Cascades. Total Cascade snowfall tonight through Sunday will be on the order of 10 to 20 inches. Transitory ridging shifts over the area mid to late Sunday afternoon. Shower activity will gradually decrease Sunday afternoon and be more tied to higher terrain. There will be a short-lived lull in precipitation Sunday evening into Monday morning. Models continue to show a weak atmospheric river spreading into southwest Washington and far northwest Oregon between 06Z and 12Z Monday. The GEFS and EPS valid 00Z Tuesday indicate Integrated Water Vapor (IVT) values around 350-400. There are model differences in regards to the max precipitation core. The NAM focuses heavier precipitation along the north Oregon coast Monday afternoon, followed by another surface wave focusing on the central coast. The ECMWF focuses the precipitation core over southwest Oregon, similar to the GFS. Preliminary QPF forecast amounts 18Z Monday through 18Z Tuesday look to be 1.5 to 3.0 inches for the Oregon Coast and Cascades. Will need to monitor the more responsive coastal rivers such as the Grays in SW WA. Weishaar .LONG TERM...TUESDAY NIGHT SATURDAY...The aforementioned atmospheric river exits the region by Tuesday night. Another weak, transitory ridge shifts across the area Wednesday. The WPC 500 mb cluster analyses are in good agreement suggesting some degree of 500 mb ridging centered along the coast. However, a majority of EPS ensembles for KPDX and KSLE show some light QPF Wednesday. The deterministic models show more variance Thursday. The ECMWF brings another short-wave through the area, while the GFS is weaker with the system. The cool and unsettled pattern looks to persist through the remainder of the long term period. Weishaar && .AVIATION...06Z TAFs...A broad low pressure areas now pushing into the Pac NW. First front moved across earlier in the evening, but now another front is pushing towards the coast. This front will bring MVFR and brief heavy rain as it moves inland through 09Z. Then, precipitation will be more showery, with mix of MVFR and VFR clouds. Upper low farther offshore will push onshore late tonight into early Sunday am. As it does, will see winds gradually turn more westerly. Still breezy, with gusts 35 to 45 kt along the coast, and 20 to 30 kt inland. Wind gradually easing through the day, with conditions gradually improving to mostly VFR after 20Z. For detailed regional Pac NW aviation weather information, go online to: https://weather.gov/zse KPDX AND APPROACHES...MVFR with rain as wait for front to pass over region. Current timing puts front moving across PDX Ops area between midnight and 1 am. Expect MVFR CIGS overnight into Sunday am, with transition to mostly VFR later Sun afternoon. Breezy south winds tonight into early Sunday, with gusts 20 to 30 kt after 07Z, then turning more westerly later Sun am into the afternoon, with winds easing Sun afternoon. /Rockey && .MARINE...Strong low offshore is producing hazardous conditions across the coastal waters. Buoy 46050 which is just ahead of the cold front is currently gusting to 43 kt with seas 16 ft at 9 sec. Expect strong winds with gusts up to 50 kt possible with heavy showers. Seas will respond across the waters into the mid teens this afternoon and then will diminish for a brief period behind the front. Low end Gale gusts around 35 kt will continue into tonight with convective showers. Another round of strong winds will move in late Saturday night as the bent back occlusion from the low arrives. This area of southwesterly winds, which is expected to overspread the waters from west to east between 10 PM Saturday and 5 AM Sunday, has the potential to bring several hours of sustained winds between 30 to 40 kt winds and gusts up to 50 kts. There is still some uncertainty on where the low will make landfall and therefore where the strongest winds and highest seas will be. The most recent run of the NAM nest, which is a pretty reliable model for marine winds, has the low moving onshore right over the Columbia River Bar; same is true for a couple other hires models which brings weaker winds near the mouth of the Columbia Sunday morning. The fresh westerly swell that will be in the upper teens by Sunday morning will move onshore with a highly variable wind field as the low makes landfall; this will make for a chaotic sea state with combined waves into the low 20s. There's a short break in wind and wave action Sunday afternoon and evening. However, Sunday night southerly winds are forecast to pick back up in response to an approaching cold front associated with another low pressure system located further northwest in the Gulf of Alaska. Ultimately, another period of Gale Force winds is possible Sunday night through Monday afternoon. In addition, a westerly swell from the same system well to our northwest will drive seas back up into at least the low to mid teens by early Tuesday morning. Seas are unlikely to fall below 10 ft through the end of the day Wednesday, and it's possible that they will stay at or above 10 ft even through the end of the work week. -BMuhlestein/Bumgardner && .BEACH HAZARDS...Hazardous beach conditions are likely late Saturday night through Sunday afternoon as a westerly swell moves onshore. This will produce marginal high surf advisory conditions for beaches between Astoria and Florence with breakers up to 23 ft possible. The large area of strong westerly winds coupled with a growing westerly swell could produce favorable conditions for dynamic fetch to occur leading to higher wave heights and potentially higher breakers. This would push conditions into Advisory criteria with breakers around 25 ft but only for a brief period, 3 maybe 6 hours. Either way people can be swept off rocks and jetties and drown while observing high surf. Higher than normal water run-up is possible on the beaches and low-lying shoreline. -BMuhlestein && .PQR WATCHES/WARNINGS/ADVISORIES... OR...High Wind Warning until 5 AM PDT Sunday for Central Oregon Coast-North Oregon Coast. Winter Weather Advisory from 7 PM PST this evening to 5 PM PDT Sunday for Cascades in Lane County-Northern Oregon Cascades. WA...Winter Weather Advisory from 7 PM PST this evening to 5 PM PDT Sunday for South Washington Cascades. PZ...Small Craft Advisory from through 5 AM PDT Monday for Columbia River Bar. Gale Warning until 11 AM PDT Sunday for coastal waters from Cape Shoalwater WA to Florence OR out 60 nm. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland