998 FXUS66 KMFR 061515 AFDMFR Area Forecast Discussion National Weather Service Medford OR 815 AM PDT Mon Sep 6 2021 .UPDATE...Marine layer clouds along the coast were less extensive than expected, with very few of them even residing offshore. Some clouds did push into the Coquille Valley, and into portions of the Umpqua, but otherwise, smoke is the primary and far dominant feature on satellite imagery this morning. Have made some changes to account for these observations, but no other updates were necessary. The warming trend should continue through tomorrow, then the pattern change expected late Tuesday into Wednesday should usher in some more seasonal temperatures, as well as hopefully some improved ventilation. For more details on this, see the previous discussion below. -BPN && .AVIATION...06/12Z TAFs...The primary forecast issues through the TAF period will be reduced visibilities and obscurations in smoke, and coastal low clouds and fog. Along the coast and just offshore, marine stratus mainly confined to Cape Blanco north close to North Bend and even then the latest satellite image shows a thin strip. Marine stratus is also south of Brookings. The expectation is for North Bend to see saw back and forth between VFR and IFR ceilings for a 2-3 hour period early this morning and for that reason have included a TEMPO group in the TAF. Otherwise the marine stratus should burn towards the coastline late this morning before reforming early this evening into tonight. Thick smoke from the fires in the region will result in areas of MVFR/IFR visibilities, through the TAF period, including Medford and Klamath Falls. -Petrucelli && .MARINE...Updated 800 AM PDT Monday 06 September 2021...Moderate north winds will persist through tonight as a thermal trough remains along the southern oregon coast. Northwest swell will slowly decrease into Tuesday. Small craft advisory level conditions with gusty winds and steep seas are expected from Cape Blanco southward into this morning, then expand across most the waters this afternoon into tonight. Winds will diminish late Monday night into Tuesday. Late in the week, a return of gusty north winds and steep seas is possible. -Petrucelli && .PREV DISCUSSION... /Issued 516 AM PDT Mon Sep 6 2021/ DISCUSSION... Comparing the 06Z HRRR Smoke Model this morning to ground truth indicates that the Near Surface Smoke depiction from the model is a bit over-optimistic in it's depiction. Using that level from the model along with the Vertically Integrated Smoke provides a better depiction of what's going on with the smoke and, likely, what will go on for the next 48 hours. In short, we've seen very good air quality work it's way into the Roseburg area and much of the Grants Pass area overnight into this morning. Also, there's been some improvement in the Applegate and Medford areas as of 345am PDT per real-time data trends, though AQI is still mostly above 100. For today, the combined effect of high pressure expanding northward from California and low pressure offshore is expected to result in smoke expanding north and westward again across Josephine County, into the Roseburg area, and to about the Curry County coast. Beleaguered western Siskiyou, Jackson, and eastern Douglas County residents and visitors will see another day of poor air quality as smoke converges there. On the bright side, from a smoke perspective for those areas, temperatures are likely to be held down about 10 degrees from what they'd otherwise be- so a high of 90F is expected for Medford instead of 100F. Additionally, it's quite likely that today will be the rock bottom of the smoky times in terms of combined magnitude and duration across many areas- such as Jackson County- with significant improvement in air quality likely later Tuesday into Wednesday. Moving on from the topic of smoke, we have a little more marine layer in the Umpqua and Coquille valleys this morning, mainly from Roseburg westward, as a trough of low pressure scrapes by from the north. This will dissipate during the course of the morning. The mid to upper level flow will become increasingly southerly today as the center of a strong area of high pressure in the upper levels shifts inland across California into Nevada. Low pressure west of California will move north-northeastward west of the coast on its way to Vancouver Island through Wednesday morning. This low is expected to move over our coastal mountains area Tuesday afternoon through Wednesday morning, pushing a mostly dry cold front across the forecast area. We do have a chance of showers in the forecast for the coastal ranges, where some light precipitation- less than a tenth of an inch- is possible. For most of the area the big item of interest related to this front will be the expected lifting and push to the northeast of the extensive, persistent smoke across the area. Smoke in the forecast has been updated to be consistent with expectations. Of note, since temperatures have been held down due to the smoke in much of the center of the forecast area and will be again for much of Tuesday, high temperatures between Tuesday and Wednesday are likely to be pretty similar in that area. That's because we're expecting much less smoke Wednesday. All in all, since little to no rain is expected on the fires across the area, smoke production is not likely to change much. What happens Tuesday into Wednesday is that most of the smoke that's been stuck in the area will lift and move out. Once things settle some Wednesday night into Thursday smoke will return, at least at times, to some areas. Thursday night into Friday another shortwave trough is expected to move through bringing a possibility of showers and isolated thunderstorms to areas east of the Cascades. This is likely to lift out some smoke again. Another shortwave trough is expected to move through Saturday night into Sunday, though models differ on strength and related details with that one. Again, this will likely stir the smoke and move some of it onward versus allowing it to loiter. As we head toward mid month, the periodic shortwave troughing continues, but what we still aren't seeing is any clear precipitation producing weather systems. The pattern is such that it wouldn't take much to flip the switch to wetter, but we're still not seeing that. Ensembles do suggest higher probabilities of precipitation in the Sep 14th-21st time frame. ~BTL && FIRE WEATHER...Updated 515 AM PDT Monday, 06 September 2021... There have been significant RH rises in the past 24 hours across much of FWZs 616 and 617 per this morning's obs, and, to a lesser degree these 24 hour RH rises extend south and eastward across portions of the Oregon Cascades, Jackson County, and Lake County this morning, likely due to the fringe effects of a shortwave trough that's moving through mostly north of us. This has led to a bit more marine layer across the Coquille Basin this morning and we're expecting some in portions of the Umpqua around sunrise. Otherwise, winds will be lighter across the area today as the mid-upper level flow becomes more south to north oriented with time. Extensive smoke is expected to move back into the Grants Pass and Roseburg areas, and the ongoing thick, extended smoke episode in western Siskiyou, Jackson, and eastern Douglas counties will continue. This smoke will keep temperatures down by about 10 degrees again from what it otherwise would be today. Tuesday into Wednesday the upper level trough we've been keeping a close eye on will move north-northeastward west of the coast. Some showers will be possible on the west side with the greatest possibility being along and near the coastal ranges. We've still got the Fire Weather Watch for FWZs 624 and 285 for Tuesday afternoon and evening. Overnight, the possibility of expanding the watches to other areas was considered- particularly for FWZ 620 covering much of Josephine County and, to a lesser degree, across portions of 280, 281, 284, 622, and 623. Local Fire Weather Guidance and SPC HREF indicate we'll be in or near RFW criteria in these areas. However, it appears that the duration of conditions is most likely to not reach criteria in those areas, and there's also some uncertainty regarding the strength of wind gusts. Therefore, chose to headline this concern for now and we'll continue to keep an eye on it and coordinate about it today with IMETs on site. While temperatures will peak Tuesday, some areas that have been significantly smoke effected are likely to reach highs close to Tuesday's values on Wednesday due to expected significant reduction in the smoke. From Thursday through mid month a shortwave trough is expected to move through every 2-3 days. This should keep smoke from being as much of a problem as it has been lately. One of these shortwave troughs is expected on the east side Friday with some showers and isolated thunderstorms possible. Thereafter, precipitation chances look minimal while temperatures linger near normal for this time of the year. ~BTL && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Fire Weather Watch from Tuesday afternoon through Tuesday evening for ORZ624. CA...Fire Weather Watch from Tuesday afternoon through Tuesday evening for CAZ285. Pacific Coastal Waters...Small Craft Advisory until 5 AM PDT Tuesday for PZZ350-370. Small Craft Advisory until 5 AM PDT Tuesday for PZZ356-376. $$