556 FXUS66 KPQR 161057 AFDPQR Area Forecast Discussion National Weather Service Portland OR 357 AM PDT Sun Oct 16 2022 .SYNOPSIS...Offshore flow persists this morning, leading to warm temperatures in exposed areas while wind-sheltered valleys start out the day much cooler. Inland areas north of roughly Salem will see another day of record warmth today, while a switch to onshore flow begins to cool off the remainder of the forecast area. Monday and Tuesday will still be warmer than usual for mid-October, just not by as much. Temperatures turn upward again Wednesday, potentially challenging records again. This year's rainy season likely begins in earnest Friday or Saturday as the first in a series of Pacific frontal systems move across the Pac NW. This pattern change will probably be the end of our summer-like warmth for the season. && .SHORT TERM...Today through Tuesday...This morning's satellite imagery continues to have a very summer-like look to it, with mostly clear skies inland and solid marine stratus along the coast. With the cloud cover and a return to onshore flow, Seaside and Tillamook will certainly not pull off another day of near-90 degree warmth today. In fact, either location will be lucky to reach 70 degrees today as warm temperatures and thermal low pressure inland draw a robust onshore flow into the Coast Range as today progresses. Eventually this onshore push will work its way into the Cascades tonight and Monday, leading to some cooling although temps will likely remain a few degrees above seasonal norms. Meanwhile, dry and warm E-NE flow persists north and east of Salem. A glance at the MSLP readings at 2 AM indicates a pressure minimum near Salem, which is likely the boundary between warm and dry offshore flow to the north and east and increasingly moist onshore flow to the south and west. Latest PSL profilers and stratus pattern on satellite indicate the marine layer is deeper to the south, with a 2000-2500 ft marine layer at North Bend and a nascent 1000-1500 ft marine layer at Astoria. Onshore flow has increased the past couple of hours at both Eugene and Corvallis Airports, and stratus has pushed well into the Coast Range gaps to their W-SW. It remains uncertain whether clouds will actually form a ceiling in the southern Willamette Valley this morning. But the strengthening onshore flow gives confidence that models are correct in bringing several degrees of cooling to the coast, Coast Range, and the south Willamette Valley versus yesterday's record temperatures. Latest NBM v4.0 guidance suggests only a 10% chance of Corvallis or Eugene reaching 80 degrees this afternoon, compared to a 30% chance for Salem and a 90% chance across the PDX metro. Offshore flow is expected to slowly diminish in general today as thermal low pressure migrates north and east. With offshore flow decreasing, it seems unlikely anyone in our CWA will reach 90 degrees today, but lowlands north and east of Salem should easily reach the 80s. Wind-sheltered valleys will likely hang onto their temperature inversions longer today, causing temps to warm slower than yesterday. Thus, places like the Upper Nehalem River valley may not be quite as warm as yesterday. But the broader valleys should have no problem warming up today in our well-mixed and dry environment. With high temperature records in the 76-83 deg F range for all our lowland climate sites today, it appears likely we will see another handful of records broken this afternoon. In fact, even at the stroke of midnight, Troutdale was only 2 degrees shy of today's high temperature record of 76 degrees, last set in 2015. With east winds expected to continue gusting for at least a few hours after sunrise, there is a chance Troutdale won't even get below 70 degrees this morning. Even the NBM gives this a 10-20 percent chance of this happening. Perhaps unsurprisingly, 100 percent of NBM members suggest Troutdale will break their 76 deg F record high today. The NBM is also bullish about Portland Airport breaking today's record high of 80 deg F, with roughly 70 percent of NBM members suggesting the record will be achieved this afternoon (our forecast for PDX is 86 degrees today). Chances for record temperatures sharply decrease southward from the Portland metro, with NBM probabilistic guidance only showing a 7 percent chance of Salem reaching their record of 83 deg F and only a 5 percent chance of Eugene reaching their record of 81 deg F this afternoon. Suspect the chances are actually a little higher than this, especially for Salem, but it does demonstrate how cooler marine air is expected to filter in from the southwest today. The warm, dry, and breezy conditions lingering north of Salem are also heightening wildfire concerns, and smoke produced by nearby wildfires are also impacting air quality. The worst air quality impacts have been around Oakridge as cool air drainage causes the smoke to pool in that area each night, with air quality impacts lingering well into each day in eastern Lane County. Smoke impacts are not just limited to Oakridge; Air Quality Advisories have been issued by our partnering agencies for much of SW Washington and NW Oregon through Monday afternoon. There may be some brief improvement in air quality Monday and Tuesday due to onshore flow and some marine clouds, but it remains questionable whether or not the marine layer will deepen enough to give slope/ridgetop portions of the Cedar Creek Fire a break from the recent, persistent, dry conditions they have generally been experiencing day and night for quite some time now. Speaking of that onshore flow Monday and Tuesday, it should bring inland temperatures down a bit, but temps will still be several degrees above normal for all but possibly the coast. Both days should feature the typical summertime pattern of coastal low clouds, extending inland to some extent each night and morning, clearing back to the coast by early each afternoon. Monday will probably be the cloudier day of the two, but afternoon sunshine should push temps into the 70s for our inland valleys both Monday and Tuesday. Models have backed off a bit on drizzle potential Monday morning, but we left a patchy drizzle mention along the coast due to our deepening marine layer. Weagle .LONG TERM...Wednesday through Saturday...Some form of ridging is very likely to return by midweek, as all 12z LREF clusters show by Wednesday. This would return us to this month's familiar pattern of strong ridging aloft, with dry air and temperatures turning warmer yet again for the latter half of the week. Assuming the PDX forecast highs around 86 deg F holds through this Sun, that would make 13 out of our first 16 days this October 80-degree days...more than doubling the previous record. Similar October records have been broken at several of our climate sites, but not by as much. There continues to be a chance PDX may tack on one or two more 80-degree days this coming Wednesday and/or Thursday if some of the warmer forecasts come to fruition. We went ahead and bumped Wednesday's temperature forecast upward, to around 81 deg F for the Portland metro. That would be day number 14 out of 19 this month with PDX reaching 80 degrees. Longer range forecast models continue to show a strong signal toward a pattern shift beginning Friday or Saturday, as some show the first in a series of Pacific frontal systems moving onshore then. Given the antecedent dry conditions, the strength and persistence of our ridge, and some model disagreement on the strength of the first front, it appears this first system will not be a soaker in terms of QPF. However it does look like there is a high chance (70 to 80 percent, based on latest cluster analyses) that subsequent systems will bring more substantial rainfall beyond Saturday. Weagle && .FIRE WEATHER...Strong high pressure aloft will remain over the Pacific Northwest Sunday. The east wind will become more confined to the west end of the Columbia River Gorge and south Washington and north Oregon Cascades today. The 00Z NAM suggests the KTTD- KDLS pressure difference will peak around -6 mb around 15Z this morning and then weaken to -3 mb mid to late afternoon. Subsidence inversions continue early this morning. These are especially notable in the Lane County Cascades where 10Z RH values were generally 20-30% on slopes and ridges. RH values for slopes and ridges of the south Washington and north Oregon Cascades and foothills were a little better and will allow the Red Flag Warning to end at 13Z. Wind will be more persistent in the south Washington Cascades today, which will maintain a threat for Red Flag wind/RH conditions through early Sunday evening. Light wind and smoke pooling in valleys may lead to increasingly stagnant air conditions in the Willamette Valley next week. Longer range models are in good agreement advertising a change to a more typical wetter and cooler Fall weather pattern towards next weekend. Weishaar && .AVIATION...12z TAFS: Coastal stratus has penetrated well into the coastal valleys as of 10Z, especially between KTMK and K6S2. Coastal areas will be primarily IFR through the morning and likely into early afternoon along the central coast. Improvement to VFR seems likely for the coast during the afternoon, but IFR to low- end MVFR stratus will return by early Sunday evening. Most inland areas to remain VFR through 12Z Monday. However, high-resolution model guidance suggests IFR to low-end MVFR stratus will push up the Columbia River to near KKLS between 06Z and 09Z Monday. In addition, there is a 30-40 percent chance IFR to low-end MVFR stratus reaches KEUG around sunrise and a higher probability early Monday morning. Inland will continue to have haze or pockets of smoke from area wildfires. Additionally, KEUG and its proximity to the Cedar Creek fire still has a solid chance to see a few hour period of reduced visibility from combined moisture and smoke. Finally, as surface winds weaken at KPDX and KHIO, will see LLWS again be a threat as winds around FL020-040 will still hover at 35-40 kts tonight and well into tomorrow morning. KPDX AND APPROACHES...VFR through 12Z Monday. Only concern is the LLWS as described above. Weishaar && .MARINE...Southerly surge in full swing early this morning. Nighttime enhanced satellite imagery shows extensive stratus field over the waters as of 10Z. Wind speeds from reporting buoys were generally 10-15 kt with gusts up to 20 kt. These values fall in line with the latest model guidance. South wind persists through Monday, strongest Sunday afternoon and evening. Have capped wind gusts just below small craft advisory thresholds, but this will need to be closely monitored for potential highlights. Wind speeds diminish Monday, falling to 10 kt or less Monday evening and continuing through Tuesday. North wind returns mid- week, with possible small craft advisory gusts Wednesday afternoon. Models in good agreement showing a change to a more active pattern beginning late next week and continuing through the weekend. A series of frontal systems are expected to sweep through the waters during this period, with potential gusts up to 30 kt. Seas to remain in the 3-5 ft range through early next week but could increase to around 6-7 ft by Tuesday as an enhanced westerly swell arrives in the coastal waters. Seas look to exceed 10 ft mid to late next week. Weishaar .PQR WATCHES/WARNINGS/ADVISORIES... OR...Red Flag Warning until 6 AM PDT early this morning for Mt. Hood National Forest West of Cascade Crest-North Oregon Cascade Foothills-Willamette National Forest. WA...Red Flag Warning until 6 PM PDT this evening for Extreme South Washington Cascades and Foothills. PZ...None. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland