Area Forecast Discussion
Issued by NWS Portland, OR
Issued by NWS Portland, OR
854 FXUS66 KPQR 251056 AFDPQR Area Forecast Discussion National Weather Service Portland OR 356 AM PDT Tue Jun 25 2024 .SYNOPSIS...Another day of warm, dry conditions is expected as a weak ridge overhead shifts eastward through the day. An upper level trough will then bring relatively cooler temperatures for Wednesday and Thursday with increasing chances for rain showers. Rainfall totals aren`t expected to be significant across most of the area. Warm and dry conditions will return Friday and Saturday with near normal to slightly above normal temperatures. && .SHORT TERM...Now through Thursday Night...Another warm day is in store today before a cooldown comes Wednesday and Thursday. Shortwave ridging remains in palace across the PNW while a large upper level trough is located across the northeast Pacific. The transient ridge will keep skies clear and will support temperatures 5-10 degrees warmer than yesterday through the Willamette Valley with highs peaking in the mid 80s to around 90 in a few spots. NBM probabilities show a 50-80% for temps to reach at least 85 and a 20-50% chance of reaching 90 or higher. The coast will remain cooler with temps peaking in the mid to upper 60s. Riding moves eastward through the day while the trough off the coast amplifies and shifts southwest flow more southerly. A surface low supported by the trough will move eastward, lifting a weak warm front through the region Wednesday afternoon, introducing a slight chance (10-30%) for showers, mainly across the Coast Range from Lincoln City northward and the Cascades in Washington. A better chance for showers will come Wednesday evening into the overnight hours as a weak cold front comes onshore and passes through the area. PoPs peak late Wednesday into Thursday morning, 30-70% north or Salem and 10-30% south of Salem. Given the weak nature of the front and limited moisture, QPF totals are not expected to amount to anything decent for much of the area. NBM guidance suggests a wide range for 0.1" across the area, the Coast Range north of Lincoln City sits at a 40-60% chance, 20-30% north of Salem and less than 10% south of Salem. The Best chance will be across the Washington Cascades at 60-80%. Much cooler temps are expected on Wednesday, peaking in the low to mid 70s in the Willamette Valley and in the upper 50s to low 60s along the Coast. Thursday will be a few degrees cooler across much of the area. -Batz .LONG TERM...Friday through Monday...The trough will exit the region late Thursday and will bring an end to any remaining showers. Cluster analysis shows good agreement in weak ridging or zonal flow developing in the wake of the trough which will help support warming temps to end the work week. Highs for the Willamette Valley should rise back into the upper 70s to low 80s Friday and Saturday as NBM guidance indicates a 40-60% chance of temps reaching or surpassing 80 both days. Another weak short wave crossing the Gulf of Alaska begins to shift southward along the west coast which could bring another round of light showers Saturday night. -Batz && .AVIATION...High pressure remains over the region, with dry mild southwest flow aloft. VFR expected through the forecast period. However at the coast spotty MVFR to IFR cigs may form (10-30% chance) 12Z-16Z Tue. For tonight upper trough approaching will increase southwest flow inducing stronger onshore flow at the low levels. This will likely bring stratus to the coast later tonight with probabilities increasing to 60-80% after 09Z Wed. Winds generally northerly less than 10 kt today, but 10 to 15 kt at the coast this afternoon. Winds back to southwest tonight. PDX AND APPROACHES...High pressure with mild dry southwest flow aloft will maintain VFR under clear skies. && .MARINE...High anchored off the Pac NW weakens today as a weakening trough moves through the waters tonight into Wednesday. As a result will see a wind reversal late tonight into Wednesday from northerly to southwesterly. Winds expected to remain below 20 kt. Seas remain in the to 4 to 6 ft range through most of the week as a westerly swell moves across the waters. && .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