Area Forecast Discussion
Issued by NWS Portland, OR
Issued by NWS Portland, OR
809 FXUS66 KPQR 231725 AAA AFDPQR Area Forecast Discussion...UPDATED National Weather Service Portland OR 1024 AM PDT Thu May 23 2024 .SYNOPSIS...Weak high pressure brings a brief period of warmer and sunnier conditions today. Cooler and cloudier conditions quickly return as another trough brings a chance of showers back to the area Friday and Saturday. Medium range models hint at a more sustained period of warmer and drier weather Sunday into early next week. && .SHORT TERM...Now through Saturday Night...Shower activity has mostly ended across the area early this morning as an upper level trough departs east of the Cascades, with a few lingering radar echos noted over the High Cascades in the vicinity of Mt Hood. Otherwise, partial clearing is depicted on satellite imagery in the lee of the Coast Range as drier northwest flow starts to work into the region. Conditions will continue to improve through the day today as a transient shortwave ridge moves overhead, with cloud cover gradually eroding and revealing mostly sunny skies by later this afternoon. Modest height rises and sunny skies will allow for much warmer temperatures than recent days as highs climb into the upper 60s to near 70 across much of the area. The shift to warmer and drier weather will be short lived as the next trough embedded in the large scale northwest flow regime arrives early Friday. This will bring a return of showery weather with cooler and cloudier conditions Friday into the weekend as temperatures trend back down into the upper 50s to low 60s through Saturday. QPF amounts remain fairly modest through the weekend, with guidance generally depicting around a quarter to a half inch of rain in the higher terrain of the Casacdes and Coast Range and lighter amounts of a tenth or two at best in the lowlands from Friday through Saturday. Snow levels may briefly lower to around 4000 feet Friday night into Saturday morning, allowing for a dusting of snow as low as the Cascade passes. Conditions will begin to improve by later Saturday as the trough departs to the east and makes way for the next period of shortwave ridging. /CB .LONG TERM...Sunday through Wednesday...Sunday looks to feature drier conditions and rebounding temperatures as benign zonal flow develops in the wake of the departing trough. WPC ensemble clusters are in reasonably strong agreement on a warming trend continuing into the early part of next week as a stronger ridge builds somewhere between the Great Basin and the Rockies, leaving the Pacific Northwest in warmer and drier southwest flow aloft. Therefore expect temperatures to reach well into the 70s for most area both Monday and Tuesday, with probabilistic guidance depicting a 30-40 percent chance to reach 80 degrees in the Portland area and closer to a 20-30 percent chance over other parts of the Willamette Valley. Guidance remains in reasonable agreement into the middle of next week as most models hint at some semblance of upper level troughing returning to the region, albeit with some differences in timing, strength, and position. In terms of sensible weather, look for increasing shower chances again by Wednesday of next week, with temperature falling back into the 60s. /CB && .AVIATION...Generally VFR conditions with CIGs around 3500-6000 ft. High pressure will continue to develop over the air space and result in VFR with CIGs above 7000 ft. Isolated pockets of MVFR and IFR conditions are being observed, but those are expected to improve to VFR over the next few hours. Winds will remain westerly and light. Next system will bring a return of clouds and light precipitation to the airspace. Look for precipitation to start along the coast around 09Z Friday with a 55%-75% probability of MVFR conditions starting around the same time. Precipitation will continue spreading inland and reach inland locations starting around 17Z Friday with a 50%-70% probability of low end-VFR/high- end MVFR conditions starting around the same time. PDX AND APPROACHES...VFR conditions with CIGs around 4000-5000 ft which will slowly break up over the next few hours. Winds remain fairly light. Clouds and precipitation will return starting around 17Z Friday with a 60-70% probability of low end-VFR/high- end MVFR conditions starting around the same time. /42 && .MARINE...Today the region will see a brief break from the active conditions as a transitory shortwave ridge of high pressure shifts overhead leading to lighter winds, and decreasing seas to 4-5 feet at 8 seconds by the afternoon hours. However, another low pressure system and attendant frontal boundary swings into the region from the NNW Friday and Saturday bringing a return of active weather. Seas build towards to 7 to 9 feet at 8 to 9 seconds on Saturday before subsiding towards 3 to 5 feet on Sunday into early next week. Given the wave heights/periods on Saturday seas will once again be fairly steep. Looking ahead, large scale upper-level flow then turns more W-SW towards the middle of next week with some guidance hinting at yet another weak weather disturbance moving into the region around Wednesday - confidence in timing and impacts remain low at this time. -Schuldt && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland