National Weather Service (2024)

Area Forecast Discussion
Issued by NWS Portland, OR

-- Highlight Changed Discussion --

-- Discussion containing changed information from previous version are highlighted. --221FXUS66 KPQR 270944AFDPQRArea Forecast DiscussionNational Weather Service Portland OR244 AM PDT Thu Jun 27 2024.SYNOPSIS...
-- Changed Discussion --
Scattered showers continue across NW Oregon and SWWashington through Thursday with another day of below normaltemperatures, peaking in the upper 60s to low 70s inland.Temperatures raise to near to above normal Friday into Saturday,back into the 80s inland, before another weak weather systemlowers temperatures a few degrees and brings another round ofscattered showers, mainly for the coast and higher terrain lateSaturday into Monday. Rising temperatures and dry weatherreturns Tuesday into at least midweek.
-- End Changed Discussion --&&.SHORT TERM...
-- Changed Discussion --
Thursday through Saturday...Water vapor satelliteimagery as of 2 AM Thursday shows the upper level trough axishas pushed inland, and surface observations indicate thesurface front has done the same. Scattered showers did spreadinland ahead of the front Wednesday evening, and radar imageryshows showers continuing currently, mainly along the coast andhigher terrain with a few showers in down to valley floorsaround and north of the Portland metro area. A weak shortwavealong the back end of the upper trough will allow showers tocontinue through this afternoon for the mentioned areas and thenorthern Willamette Valley. Daytime temperatures will be similarto yesterday with inland valleys only peaking in the upper 60sto low 70s and upper 50s to 60s along the coast. Additional rainaccumulation will be limited with anywhere from a trace to 0.15inch, up to 0.25 to 0.5 inch for localized spots in the Cascadesnorth of Santiam Pass that have consistent showers.After the trough moves to the east tonight, upper level flowbecomes more zonal Friday into Saturday with a surface thermaltrough forming over southern Oregon. This will bring dry andwarmer weather to the region. Inland temperatures are expectedto rise into the upper 70s to low 80s with mid to upper 60salong the coast. Skies will be mostly sunny Friday, but anotherapproaching upper trough will bring increasing cloud coveracross the region Saturday with the return of onshore flow. -HEC.LONG TERM...Sunday through Wednesday...Ensemble guidance is invery good agreement of a weak upper level trough moving throughthe PacNW Sunday as 100% of the WPC 500mb clusters indicate thispattern. Another round of scattered showers are expected withthis trough, though coverage looks to be less expansive thanthe current trough as the surface forcing looks to be limited.About a 15-30% of showers is forecast along the coast andterrain as orographics will be the main forcing for showers.Temperatures may lower a few degrees back to near normal (mid toupper 70s).Some ensemble members as well as deterministic models indicatethe potential for another shortwave on the back end of thetrough Monday which would allow shower chances and near normaltemperatures to continue. By Tuesday into Wednesday, 85% of theWPC clusters indicate a ridge building over the eastern Pacificwith the other 15% indicating zonal flow. Dry weather isexpected to return with either of these patterns withtemperatures rising back into at least the low 80s. -HEC
-- End Changed Discussion --&&.AVIATION...
-- Changed Discussion --
Onshore flow persists through Thursday as an upperlevel trough axis shifts farther east through the day. Conditionsinland will be mainly VFR with a brief period of MVFR CIGs thismorning between 15-20Z with CIGs dropping to around 1500-3000 ft.The coast will be trickier with conditions fluctuating betweenVFR with mid level clouds at 3000-6000 ft and MVFR/IFR (or lower)with clouds below 2000 ft. Scattered light rain showers willcontinue to plaque the region into Thursday afternoon beforetapering off this evening around 3Z. Winds will remainsouth/southwesterly at 5-10 kts through 18-22Z before turn to thewest/northwest late this morning and into the afternoon.PDX AND APPROACHES...VFR deck with main deck at 3000 to 5000 ftto start before CIGS likely drop below 3000 ft Thursday morningaround 15-20z. Showers remain largely in the vicinity of the sitethrough the morning before increasing in coverage slightly earlyThursday afternoon before drying out by the evening. -Batz
-- End Changed Discussion --&&.MARINE...
-- Changed Discussion --
South/southwest flow around 10-15 kts will continuethrough the morning before turning to the northeast as highpressure offshore will return briefly through early Sat. At sametime, will see thermal low pressure over far southwest Oregon intonorthwest California. As such, will get back into some northerlywinds, with gusts 20 kt in afternoons/evenings.Yet another weak low pressure arrives later Sat, with windsflipping back to the west or southwest. Gradients weaker, so windsnot expected above 15 kt. Seas stay in the 4 to 6 ft range.
-- End Changed Discussion --&&.PQR WATCHES/WARNINGS/ADVISORIES...OR...None.WA...None.PZ...None.&&$$www.weather.gov/portlandInteract with us via social media:www.facebook.com/NWSPortlandwww.twitter.com/NWSPortland