Area Forecast Discussion
Issued by NWS Portland, OR

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000 FXUS66 KPQR 102110 AFDPQR Area Forecast Discussion National Weather Service Portland OR 209 PM PDT Sat Jun 10 2023 .SYNOPSIS...
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The warming trend continues into Sunday, with temps peaking Monday before stronger onshore flow moderates the air mass, returning temps closer to mid-June normals. Spotty drizzle is possible Tue night/Wed due to deep onshore flow, but otherwise the district should remain dry throughout the week once this morning`s precipitation ends.
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&& .SHORT TERM...
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Tonight through Tuesday...A warming and drying trend returns to the region as a a distended trough with a low pressure moves inland around central California through the weekend and into Monday. As this low move inland, a ridge of high pressure will move eastward from the central basin across the Cascades and into the Pacific NW. Which sets up a col pattern with the center or saddle point of this synoptic feature centered over the Pacific NW. As the aforementioned ridge of high pressure builds, a surface thermally induced trough will extend northward from the OR/CA border and will result in mostly clear and warm daytime temperatures. Daytime highs are expected to be in the in the low to mid 80s on Sunday, in the upper 80s to low 90s Monday as 11C-14C 850 mb temperatures will mix down. The coast will run in the mid 60s to low 70s as persistent onshore flow will mitigate daytime highs. At this time, Monday looks to be the hottest day for this warming trend. Tuesday, conditions look to start cooling as a surface low, well offshore moves southward, along with an upper level low that will push inland near the Washington/Canada border. Model are suggesting that there could be enough QPF to support some light drizzle along the coast Monday night/Tuesday morning. Otherwise, the forecast remains dry across the region, but with a cooling trend on deck for the middle of the upcoming week. /42 .LONG TERM...Tuesday night through Saturday: The model spread that began to appear this time yesterday, has since retreated to better consolidation similar to what was shown 48 hours ago. Tuesday night continues to show an upper shortwave rapidly crossing British Columbia while clipping far northern Washington. Precip will stay to the north of our area, but this will also serve to reinforce westerly flow and the marine layer as a result. Wednesday`s high temps will be roughly 5 degrees cooler than Tuesday`s and 15 degrees cooler than Monday`s peak. An eastern Pacific ridge will extend an axis northeasterly toward British Columbia lasting through most of Thursday and Friday. This will keep the region roughly under the warmer side of zonal flow and serve to shunt north, the main precipitation effects from passing shortwaves. Additionally, northwest to north flow from surface high pressure offshore paired with low pressure inland and also along the OR/CA coastal border, will keep conditions breezy each afternoon and evening, especially at the coast. High temperatures, however, will remain in the mid to upper 70s with low temperatures around 50 degrees and fairly close to 30 year normals. Friday night and Saturday feature 70 percent of model and ensemble members brining some form of trough to the PacNW. Consensus shows the vast majority of precipitation heading north of the area into B.C. placing less than 0.20" of precip at most across SW Washington and NW Oregon. But there are about 15% of runs from the overall model suite which do bring about 0.50 inches or more of rain ending Saturday afternoon. Will favor the lighter solutions at this time. /JBonk
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&& .AVIATION...
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At 21z Saturday, skies were mostly clear across the area aside from a broken MVFR cloud deck hanging strong across southwest WA and at KAST. Expect this broken cloud deck to become scattered by 00z Sunday as daytime heating peaks, resulting in VFR flight conditions at all of the TAF sites. Then, IFR to low-end MVFR cigs are likely to develop at KAST around 03-04z Saturday and at KONP by 08z Saturday (80% chance at both TAF sites). Also expecting at least some cloud cover to develop along portions of the Cascade foothills towards 12z Sunday before backbuilding into eastern portions of the Willamette Valley (mainly to the east of the I-5 corridor) shortly thereafter. Right now, KTTD and KUAO have the highest chance for MVFR cigs between 12-18z Sunday morning (60-70% chance). KSLE, KEUG, and KPDX have around a 50% chance. Lastly, expect dry conditions at all TAF sites as high pressure aloft begins to rebuild into the area. Onshore surface winds will also become breezy during the late afternoon and early evening hours on Saturday as a diurnal sea breeze pushes inland and surface pressure gradients tighten. For detailed Pac NW aviation weather information, go online to: http://weather.gov/zse KPDX AND APPROACHES...Expect VFR flight conditions to continue through at least 10-12z Sunday with mostly clear skies. There is a 50% chance of MVFR cigs between 12-17z Sunday as a cloud deck over the Cascade foothills attempts backbuilding westward towards the KPDX terminal.-TK
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&& .MARINE...
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High pressure will strengthen offshore through the weekend as thermal low pressure also strengthens over NW California. This setup looks to remain in place well into next week, resulting in a prolonged period of northerly to northwesterly winds from Saturday afternoon through at least Thursday. Expect north winds to peak in intensity during the mid to late afternoon and evening hours each day, strongest over the central and southern waters to the south of Cape Falcon. Expect small craft wind gusts as high as 25 to 30 kt Saturday evening and again Sunday afternoon and evening. It appears wind gusts will not be quite as strong next week, but still likely becoming strong enough to warrant marginal small craft advisories. Expect seas to become steep and choppy each day as the northerly winds pick up. Seas should build to 6 to 10 ft Sunday afternoon and then remain within that range well into next week. Seas will be most hazardous during the afternoon and evening hours each day when wind speeds peak.-TK
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&& .PQR WATCHES/WARNINGS/ADVISORIES...
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OR...None. WA...None. PZ...Small Craft Advisory until 5 AM PDT Monday for Coastal waters from Cape Foulweather OR to Florence OR out 10 NM. Small Craft Advisory from 5 PM this afternoon to 5 PM PDT Monday for Waters from Cape Shoalwater WA to Cape Falcon OR from 10 to 60 NM. Small Craft Advisory until 5 PM PDT Monday for Coastal waters from Cape Foulweather OR to Florence OR from 10 to 60 NM.
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