797 FXUS66 KMFR 112126 AFDMFR Area Forecast Discussion National Weather Service Medford OR 226 PM PDT Mon Aug 11 2025 .DISCUSSION... Overview: Notable items of interest continue to be the current heat wave and elevated/critical fire weather conditions through this week. Recent model guidance has introduce a small chance for thunderstorms on Saturday. This is in addition to the chance for showers along/near the coast and the Umpqua Basin Friday through Saturday. Otherwise, temperatures will start to cool off by Thursday with highs near normal. In fact, a welcoming trend of temperatures below normal are in the forecast Friday-Sunday. Further Details: 500mb heights will start to drop over the forecast area later today, and this will allow for a trough to squeeze in between two areas of high pressure tomorrow through Thursday. This trough will essentially be right over the forecast area tomorrow. This will be associated with a dry frontal passage which will bring increased wind speeds in the afternoon/early evening coupled with critically low RH values. The trough gets hung up in between an area of high pressure over the Gulf of Alaska and another area over the Desert Southwest through this stretch. This may result in elevated to critical fire weather conditions Tuesday through Thursday. Please see the Fire Weather section below for further details. Dry weather expected through much of this week, but by Friday a stronger and deeper trough develops and pushes into British Columbia and the PacNW. This will be accompanied by plenty of moisture, but the heavier rainfall amounts will likely be well to the north of our forecast area. That said, there will be areas along/near the coast and the Umpqua basin that could receive a few hundredths to a tenth of an inch of rainfall. Instability is progged to be nonexistent--to very low--on Friday, so not expecting thunderstorms at this time. However, on Saturday there is some guidance suggesting a couple hundred J/kg of MUCAPE could be present. While these MUCAPE values are on the low end, we cannot rule out the small chance (10%-20%) for thunderstorms along/near the Cascades and eastside areas Saturday afternoon. This is Day6 so we still have some time to refine these details. At this time we are not expecting widespread severe weather, but isolated areas could see a strong storm or two with lightning and strong winds as the main threats. && .AVIATION...11/18Z TAFs...VFR levels are present across northern California and southern Oregon to start the TAF period. Stable atmospheric conditions will support VFR levels continuing for inland areas, with normal diurnal breezes expected. Marine stratus is expected to bring IFR to LIFR conditions to the Oregon coast this evening, with clearing possible late Tuesday morning or early in the afternoon. -TAD && .MARINE...Updated 200 PM PDT Monday, August 11, 2025...Continuing north winds are supporting steep seas across area waters through this afternoon. This evening, inner waters (0-10 nm from shore) look to fall below advisory levels while outer waters remain steep through Tuesday evening. A weak thermal trough pattern could also rebuild steep seas in inner waters south of Cape Blanco on Wednesday evening through Thursday evening. Past Thursday, winds ease and turn more northwest as a low pressure system sets up in the Gulf of Alaska. This system may send elevated northwest swell into area waters late Friday and through the weekend, with periods of swell- built steep seas possible on Saturday and Sunday. -TAD && .FIRE WEATHER...Updated 200 PM PDT Monday, August 11, 2025... Hazardous daytime temperatures remain in the forecast under a persisting upper ridge. An Extreme Heat Warning in place for parts of FW Zones 620, 622, 280, and 281 and a Heat Advisory is in place for parts of FW Zones 616, 624, 284, and 285. While dry conditions are also forecast for today, forecast afternoon breezes still look to remain below critical levels. A weak upper trough approaching the area tonight will help to improve overnight recoveries, although periods of northeasterly breezes overnight peaks and ridgelines will keep RHs on the 30-40% range. That upper trough looks to move over the area on Tuesday and bring some instability, bringing winds up to critical levels in FW Zones 620, 622, 624, and 625. An existing Fire Weather Watch for these areas has been upgraded to a Red Flag Warning that will be in place from 2 PM through 8 PM on Tuesday. On Wednesday, weak upper troughing in a zonal flow pattern remains in place but without additional instability. Temperatures are expected to cool enough to fall below hazardous levels, but remain above seasonal highs. Daytime RH values and breezes remain near critical levels, but any improvements to these conditions may make another Red Flag Warning unnecessary. For now, a Fire Weather Watch is in place for Wednesday afternoon and evening covering the same areas as Tuesday`s Red Flag Warning. Further improvements on Thursday are making additional fire weather products for dry and windy conditions unlikely. A low pressure system developing in the Gulf of Alaska looks to guide conditions to end the week and into the weekend. On Friday, a weak front could pull daytime highs down to seasonal or below seasonal temperatures. Light rain shower chances are in the forecast for Friday afternoon and evening along the Oregon coast and into Douglas County. Behind the front, upper flow could turn southwesterly on Saturday through Monday. This flow pattern tends to bring isolated showers to western Siskiyou County as well as along the Cascades and parts of Lake and Klamath County. Initial guidance does not suggest any significant activity, but this period will be watched closely as new guidance is available. -TAD && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Extreme Heat Warning until 2 AM PDT Wednesday for ORZ024-026. Heat Advisory until 2 AM PDT Wednesday for ORZ023-029. Red Flag Warning from 2 PM to 8 PM PDT Tuesday for ORZ620-622. Fire Weather Watch from Wednesday afternoon through Wednesday evening for ORZ620-622. Red Flag Warning from 2 PM to 8 PM PDT Tuesday for ORZ624. Fire Weather Watch from Wednesday afternoon through Wednesday evening for ORZ624. CA...Extreme Heat Warning until 2 AM PDT Wednesday for CAZ080-081. Heat Advisory until 2 AM PDT Wednesday for CAZ082>085. PACIFIC COASTAL WATERS...Small Craft Advisory until 5 PM PDT this afternoon for PZZ350-356-370-376. && $$ JWG/TAD