Area Forecast Discussion
Issued by NWS Portland, OR
Issued by NWS Portland, OR
073 FXUS66 KPQR 271936 AFDPQR Area Forecast Discussion National Weather Service Portland OR 1236 PM PDT Sat Apr 27 2024 Updated aviation discussion. .SYNOPSIS...Another front will push across the region today, with rain this morning into the afternoon, then showers. Showers will continue into early next week. May have a day or two break (Wed into Thu), but more precipitation arrives to start next weekend. && .SHORT TERM...(Today through Monday)...As of 2 am, still have some lingering showers, mainly over the Cascades. Next front is offshore, and fast approaching. As such, will see rain spread back to the coast by daybreak, with rain spreading inland this morning. This front is moving at a decent pace, will will push onshore this afternoon, racing to the Cascades by late afternoon/early evening. Will trend forecasts a such, the rain transitioning to showers behind the front. Overall rainfall not all that much, with generally 0.25 to 0.50 inch along the coast into the Coast Range/Willapa Hills, and parts of the Cascades from Mt Jefferson northward. Bit less rain for inland valleys, with 0.10 to 0.25 inch expected. Once the front passes, will have cooler air aloft push inland. This will maintain showers tonight into Sunday. Lapse rates do steepen just a tad, enough such that with any warming that comes with the breaks in the clouds, could see an isolated thunderstorm. Not all that sold on the idea, but will maintain a slight chance for areas along the coast, as as inland for Sunday afternoon/evening north of a Tillamook to Estacada line. Another fast moving upper level system will push off the Pac into the region Sunday night. This will enhance the showers, with even a period of steady rain for a few hours Sun night. As this disturbance passes, snow levels will drop from 4000-4500 ft on Sunday down to 2500-3000 ft Sunday night. Could see another 2 to 6 inches of snow across the Cascades at that time. But, with more showery pattern by that time, accumulations across the higher terrain will be more random and non-uniform. But, with this being a late season drop of snow levels, may need to issue a winter weather advisory for the Cascades for Sunday night into early Monday, but will let day shift (or next few shifts) re-evaluate that scenario. /Rockey .LONG TERM...(Tuesday through Thursday)...No changes. Overall confidence is low to moderate the pattern stays rather progressive into late next week - deterministic and ensemble guidance struggle resolving the longitudinal placement of ridge/trough features going forward. Showers are expected to linger on Tuesday as snow levels hold somewhere between 2500-3500ft. Wednesday guidance has continued to trend a little drier nudging a larger scale upper-level low further north while a transient ridge glides over the region. Out of all the ensemble solutions available, this scenario is present in roughly 60% of them in addition to the latest deterministic ECMWF and GFS. Past this point model uncertainty becomes truly significant with nearly a 50/50 split between maintaining a ridge feature overhead or bringing a potent trough into the region by Thursday. Hopefully in the coming forecast runs guidance begins to show better agreement resolving the pattern mid to late week. Current confidence in the forecast by Thursday is low. /Schuldt && .AVIATION...Scattered showers continue across NW Oregon and SW Washington through Sunday, bringing lowered ceilings and visibilities at times. Along the coast and higher terrain, predominately MVFR conditions with local IFR in heavier showers expected through the period. Elsewhere, including lowland valleys, ceilings expected to hover right around the VFR/MVFR threshold, generally bouncing around between 2500-3500 ft through around 07z Sunday. Expect lower ceilings and visibilities in passing showers. Southerly winds across the airspace through around 00Z Sunday with gusts up to 25 kt along the coast and up to 20 kt for inland locations. Afterwards, winds along the coast will become more westerly with gusts up to 15 kt as southerly winds persist inland with gusts up to 10 kt through the remainder of the TAF period. Notes: The ASOS at KTTD is only available via the dial in option. The AWOS at KMMV is still out of commission. There is no estimated time of repair. PDX AND APPROACHES...Predominately VFR with rain showers. Ceilings will hover around 3500-4500 ft through the TAF period along with a 60-80% probability for MVFR conditions from 21z Saturday through 05z Sunday. Southerly winds with gusts up to 20 kt through around 00Z Sunday. Afterwards, winds will subside with gusts up to 10 kt through the remainder of the TAF period. -HEC && .MARINE...Elevated conditions persist through today, resulting in steep and choppy seas along with gusty southwesterly winds with gusts up to 30 kt. Therefore, have adjusted the timing of the current Small Craft Advisories to reflect this as conditions will start to subside by Saturday afternoon as winds become more westerly. However, this will be somewhat short lived as the next system is expected to start impacting the waters Sunday and will bring a return to Small Craft winds and seas that are expected to persist across as waters through the start of the upcoming week. /42 && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory until 8 PM PDT this evening for PZZ210- 251>253. Small Craft Advisory until 5 PM PDT this afternoon for PZZ271>273. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland