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Area Forecast Discussion
Issued by NWS Portland, OR
Issued by NWS Portland, OR
828 FXUS66 KPQR 290447 AFDPQR Area Forecast Discussion National Weather Service Portland OR 947 PM PDT Fri Jun 28 2024 .UPDATED AVIATION DISCUSSION... .SYNOPSIS... Aside from some light drizzle across the northern portions of the CWA late Saturday into Sunday, onshore flow will maintain near average temperatures into early next week. There is 30-40% chance that stronger high pressure offshore will shift over the region towards the end of next week and bring our hottest temperatures of the Summer so far. && .SHORT TERM...Tonight through Sunday...Weak upper level troughing under low level onshore flow will keep the area mainly dry with temperatures pretty darn close to average for this time of year through the weekend. A passing shortwave trough to our north will clip the region and perhaps deepen the marine layer enough to wring out some drizzle and light rain along mainly the coast, Coast Range and Cascades north of a line extending between Mt Jefferson and Newport late Saturday into Sunday. NBM probabilities for rain only climb into the 15-30% range for any given 6-hour period late Saturday into Sunday along the north coast and higher terrain. All in all, it looks like rather average and benign weather for late June. /Neuman .LONG TERM...Monday through Friday...As the upper level shortwave trough moves east of the region early next week, WPC clusters are in very good agreement of upper level ridging building over the eastern Pacific. Ensembles are in good agreement that zonal flow aloft and low level onshore will couple to bring a continuation of temperatures near to slightly (a few degrees) above average for areas away from the coast through midweek. Uncertainty in the forecast begins to grow dramatically midweek as ensemble members begin to diverge substantially on potential scenarios. While nearly all of the ensemble guidance has above average 500mb heights over the Pacific Northwest by Thursday, about 25% of the ensemble guidance suggests an upper level trough will either be approaching the region from the northwest or a different shortwave trough will be lingering across the northern Rockies to keep temperatures across the area near average. The rest suggest a pattern conducive for above temperatures, but with varying degrees of heat. At this point, it appears there`s a 25% chance that temperatures climb to 90F by Thursday across inland valleys with the probabilities rising to 50% on Friday. There is even a low probability (10%) of 100F temperatures by Friday. The NBM deterministic forecast is on the warm side of the probability distribution come next Friday, but not enough to change it so have left the forecast as is. /Neuman && .AVIATION...High pressure continues to shift eastward as a weak upper-level trough approaches the coastline expected to clip the region to the north on Saturday. Fortunately VFR conditions likely persist at inland sites through the TAF period with CIGS eventually lowering to ~5kft by Saturday evening. That said, the same can`t be said for the coast where MVFR conditions develop between 20-23z due to the aforementioned weather disturbance, deteriorating further to IFR cigs/vis by Saturday evening although confidence is only moderate regarding the exact timing at KONP/KAST. PDX AND APPROACHES...High pressure shifting eastward will continue to facilitate VFR conditions locally with typical diurnally driven northwest to northerly winds through 00-06z Sunday. CIGS gradually decrease through the period but will remain VFR. -Schuldt && .MARINE... Weak high pressure over the northeast Pacific with lower surface pressure over California and the Great Basin will more or less maintain itself into next week. A weak front will temporarily try to clip the waters tonight into Saturday and turn winds more out of the west. Otherwise, expect north to northwest winds across the waters with the strongest winds generally off the central coast of Oregon and lighter winds farther north. Winds will generally peak in the afternoon and evening hours each day. Pressure gradients appear increasingly likely to increase by early to mid next week so that there is a >90% chance that northerly wind gusts of 25-30 kt spread northward across the waters. This will in return develop steep wind driven seas of 5-8 ft with a dominant period of 7-8 seconds by Tuesday or Wednesday. /Neuman && .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