758 FXUS66 KMFR 060339 AFDMFR Area Forecast Discussion National Weather Service Medford OR 839 PM PDT Sun Sep 5 2021 .DISCUSSION...Smoke from area wildfires continues to be the main impact across the region this evening. Fires continue to burn hot over SW Siskiyou County and also eastern Douglas County with a corridor of thick smoke stretching up across the southern Oregon Cascades and spreading out eastward from there. There is a distinct dividing line across NW Jackson County though with a drive north on I-5 from Medford getting you mostly out of the smoke this evening. Grants Pass, the Illinois Valley and Roseburg points north and west are mostly in the clear at this time. The visibility here at the airport has also improved to around 3 miles, up from 1 mile around lunchtime. This probably won't last though as low-level smoke is expected to settle back in later tonight or Monday morning. Also expect some push back westward into the Illinois Valley/Umpqua Basin Monday morning. This diurnal ebb and flow of smoke can be expected through at least Tuesday morning. If there's a silver lining to the smoke, it's been that it has helped keep daytime temperatures in check. Without the smoke, highs would be closer to 100 degrees here in Medford. But, instead, it has been about 10 degrees lower. This will likely continue on Monday and Tuesday. Meantime, the only clouds across the forecast area will be marine layer low clouds and fog impacting the immediate coast overnight into Monday morning. We aren't expecting much push inland, so these should be mostly restricted to the Coos/Curry coast, but perhaps some of the inland coastal valleys as well. The next upper trough offshore will eject across the area Tuesday afternoon/night. Breezier conditions will develop Tuesday afternoon. See the Fire Weather section below for fire weather headlines. This trough will bring a chance of showers to NW sections of the CWA then, but most will likely remain to the north and west of Medford. -Spilde && .AVIATION...06/00Z TAFs...The primary forecast issues through the TAF period will be reduced visibilities and obscurations in smoke, and impending coastal low clouds and fog. Marine stratus will redevelop along the coast this evening with LIFR ceilings along with IFR/LIFR visibilities expect to affect most areas from Cape Blanco northward and Brookings southward. Thick smoke from the fires in the region will result in areas of MVFR/IFR visibilities, through the TAF period. Medford will see reduced visibilities in smoke through the day with some improvement in the early evening. Klamath Falls will likely remain near MVFR due to visibility through the TAF period. -Sven && .MARINE...Updated 820 PM PDT Sunday 05 September 2021...North winds will begin to increase this evening into Monday as a thermal trough develops 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 to develop from Cape Blanco southward this evening and tonight. Small craft advisory conditions are expected to expand across most the waters Monday afternoon into Monday night, then diminish late Monday night into Tuesday. Late in the week, a return of gusty north winds and steep seas is possible. -Sven && .FIRE WEATHER...Updated 820 PM PDT Sunday 05 September 2021...Have allowed the Red Flag Warning for winds/low RH this evening to expire as winds ease and RHs come up. No other updates this evening. It will be dry with a warming trend through Monday, although smoke coverage may temper the warming in some areas. Generally, inland highs will be 10-15 degrees above normal. Overnight humidity recoveries over the ridges will be poor to moderate through Monday night, and daytime humidities will be very low inland, especially east of the Cascades and in fire zones 284 and 285 where single digit readings are likely. Afternoon winds will be gusty today, then weaken slightly tomorrow, before increasing again on Tuesday ahead of an approaching trough. When combined with the low humidities, this will create critical conditions over portions of the area today, specifically across zone 285 and the higher terrain of eastern fire weather zone 624, where A Red Flag Warning remains in effect through this evening. Winds have trended weaker for Monday afternoon, and despite humidities remaining low, this should keep us just shy of critical values, so we have cancelled the Fire Weather Watch that was previously in effect. Winds and humidities look more concerning Tuesday afternoon, so a new Watch has been issued for nearly all of 285 and much of southeastern 624 for mOnday afternoon and evening. See RFWMFR for details. The trough on Tuesday looks to make only a glancing blow to our area, but it still could produce some light precipitation over portions of the West Side, mostly along the coast and in the Umpqua Basin, with little effect elsewhere other than the increased winds. Following the trough, it will be dry and cooler Wednesday through Friday with high temperatures near normal values, and a modest improvement to humidities. -BPN/Spilde && .PREV DISCUSSION... /Issued 247 PM PDT Sun Sep 5 2021/ DISCUSSION...Strong high pressure centered over the Sierras/Nevada will be our main weather driver through at least Tuesday morning. Weak flow aloft associated with this high pressure will maintain rather persistent conditions regarding the extensive smoke over the region and resultant air quality. Smoke models indicate the potential for some improvement during the afternoons/evenings west of the Cascades, but the highest confidence for this potential is for Josephine and western Douglas Counties (roughly along and west of I- 5). One positive aspect to the smoke (if there is such a thing), is that it is limiting high temperatures where the smoke is thickest. With this strong high pressure aloft, high temperatures should be in the 90s to triple digits across much of the region. However, thick smoke is resulting in high temperatures occurring that are around 5 to 10 degrees cooler than what model guidance indicates and this trend has been accounted for in the forecast. None the less, a relative warming trend is in place and temperatures are expected to peak on Tuesday. Cooler temperatures and better chances for smoke improvement come late Tuesday into Wednesday as the pattern begins to shift. A cutoff low currently off the California coast approaches the area late Monday into Tuesday and this will weaken the ridge some while pushing it slightly eastward. This low will open up and become a shortwave trough that gets swept into the westerlies late Tuesday into Wednesday, eventually moving inland into northern Oregon and Washington. As this happens, there will be the first chance of precipitation the area has seen in some time. However, the trajectory of this low has trended westward, so precipitation chances are limited largely from the coast range westward and into the Umpqua Basin. Additionally, any precipitation should be light, so we aren't expecting this rainfall to have any significant impacts on the area's wildfires. Winds will increase ahead of and with this trough passage Tuesday into Wednesday. These increased winds, along with better mixing, will provide at least some relief in the persistent smoky conditions. Heading into the long term portion of the forecast (Thursday through next weekend), the forecast remains a bit uncertain. Models hold onto strong ridging over the Four Corners region with weak troughing over the eastern Pacific. This will leave the region under southwest flow with multiple shortwaves to pass through during this time. None of these shortwaves look particularly impressive at this time, but there will likely be enhanced afternoon/evening breezes each day. Unfortunately, the one thing models remain fairly consistent on is the lack of precipitation potential during the extended portion of the forecast. /BR-y AVIATION...05/18Z TAFs...The primary forecast issues through the TAF period will be reduced visibilities and obscurations in smoke, and impending coastal low clouds and fog. Marine stratus will redevelop along the coast this evening with LIFR ceilings along with IFR/LIFR visibilities expect to affect most areas from Cape Blanco northward and Brookings southward. Thick smoke from the fires in the region will result in areas of MVFR/IFR visibilities, through the TAF period. Medford will see reduced visibilities in smoke through the day with some improvement in the early evening. Klamath Falls will likely remain near MVFR due to visibility through the TAF period. -CC MARINE...Updated 200 PM PDT Sunday 05 September 2021...North winds will begin to increase this evening into Monday as a thermal trough develops along the southern Oregon coast. At the same time, a 5 to 7 foot northwest swell will build into the area. Small craft advisory level conditions with gusty winds and steep seas are expected to develop from Cape Blanco southward this evening and tonight. Small craft advisory conditions are expected to expand across most the waters Monday afternoon into Monday night, then diminish late Monday night into Tuesday. Late in the week, a return of gusty north winds and steep seas is possible. -CC FIRE WEATHER...Updated 200 PM PDT Sunday 05 September 2021...It will be dry with a warming trend through Monday, although smoke coverage may temper the warming in some areas. Generally, inland highs will be 10-15 degrees above normal. Overnight humidity recoveries over the ridges will be poor to moderate through Monday night, and daytime humidities will be very low inland, especially east of the Cascades and in fire zones 284 and 285 where single digit readings are likely. Afternoon winds will be gusty today, then weaken slightly tomorrow, before increasing again on Tuesday ahead of an approaching trough. When combined with the low humidities, this will create critical conditions over portions of the area today, specifically across zone 285 and the higher terrain of eastern fire weather zone 624, where A Red Flag Warning remains in effect through this evening. Winds have trended weaker for Monday afternoon, and despite humidities remaining low, this should keep us just shy of critical values, so we have cancelled the Fire Weather Watch that was previously in effect. Winds and humidities look more concerning Tuesday afternoon, so a new Watch has been issued for nearly all of 285 and much of southeastern 624 for mOnday afternoon and evening. See RFWMFR for details. The trough on Tuesday looks to make only a glancing blow to our area, but it still could produce some light precipitation over portions of the West Side, mostly along the coast and in the Umpqua Basin, with little effect elsewhere other than the increased winds. Following the trough, it will be dry and cooler Wednesday through Friday with high temperatures near normal values, and a modest improvement to humidities. -BPN && .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 from 11 AM Monday to 5 AM PDT Tuesday for PZZ350-370. Small Craft Advisory until 5 AM PDT Tuesday for PZZ356-376. $$ MAS/MNF/BPN/SBN