052 FXUS66 KMFR 171148 AFDMFR Area Forecast Discussion National Weather Service Medford OR 334 AM PDT Sun Sep 17 2023 .DISCUSSION...Skies are mostly clear this morning. Marine stratus hugs the coast south of Cape Blanco and has filled portions of the Coquille Basin. Additionally, some scattered mid-high level clouds are drifting northward into the region. This mid-level moisture is associated with an upper level low pressure lingering off the coast of California which is bringing southerly flow to the region. Isolated convection kicked off yesterday afternoon, with a total of 48 lightning strikes focused over southwestern Siskiyou County. There remains enough elevated instability in this same area for some overnight showers/thunderstorms to occur before sunrise this morning. Confidence isn't high in this occuring and chances remain less than 20%. Later this afternoon and evening, thunderstorm chances will spread across a broader area, and isolated thunderstorms are possible again in northern California, but but also areas from southern Josephine/Jackson counties east- northeastward across the Cascades and over to the East Side. This includes Ashland, Yreka, Klamath Falls, Alturas and Lakeview. With not much change in the overall pattern expected today, afternoon temperatures will be quite similar to yesterday's values, though thicker smoke could keep high temperatures down by a few degrees. Air quality remains degraded across the region and an Air Quality alert remains in effect for Curry, Josephine and Jackson counties where smoke is expected to be most persistent through at least this afternoon. Smoke models remain optimistic that conditions will at least improve (but still remain hazy) this afternoon for these counties, but conditions could worsen east of the Cascades as smoke from the Bedrock/Lookout fires in Deschutes County moves southeastward into Klamath/Lake Counties this evening. A quick-moving upper trough will move into the PacNW tonight and across the area Monday. Lingering instability in far southern and southeastern sections of the forecast area will maintain a slight risk of thunderstorms mainly for southern Siskiyou/Modoc, but perhaps also Lake County. The rest of the area should be dry. Pressure gradients aren't that strong, but expect at least an uptick in afternoon WNW breezes. This will also begin a more noticeable cooling trend that will be reinforced by another quick-moving upper trough that will swing through Monday night into Tuesday. Thunderstorm chances diminish Tuesday as these incoming troughs push low pressure south of the region and the atmosphere stabilizes under a west to northwest flow. For the extended period, Tuesday into next weekend, an upper level trough will slide into the PacNW from the north starting Tuesday and linger over the region for the latter half of the week. Model ensembles/clustering still show some uncertainty regarding the depth of the trough, but there is general agreement in an increase in north to northeasterly winds with a tightening gradient between high pressure offshore and lower pressure inland. Overall, this will maintain a cooler pattern across a large portion of the area. The only exception could be at the coast, where the offshore winds could bring slightly warmer than normal conditions (esp Brookings). Most model solutions do track the upper low east of the Cascades, so shower potential will be highest over there (25-35% chance) around Thursday. The low gets a kick eastward Fri/Sat with temperatures nudging upward, but mostly remaining below normal for this time of year (upper 70s/low 80s). -BR-y/Spilde && .AVIATION....17/12Z TAFs...VFR conditions are generally expected to persist across northern California and southern Oregon this morning. Marine stratus has developed over areas south of Port Orford and is making efforts to build at North Bend, but substantial development seems unlikely. Coastal areas north of Cape Blanco should see some gusty winds this afternoon before those winds calm into the evening. Movement of wildfire smoke at upper levels will continue through the TAF period, with the highest concentrations over western Siskiyou County and low to moderate concentrations possible elsewhere. At low levels, most smoke is forecast to stay in northern California but low to moderate amounts may affect Curry, Josephine, and Jackson counties through the day today. A plume of smoke from the Bedrock Fire may move southward across Lake and Klamath counties near the end of the TAF period. -TAD && .MARINE...Updated 230 AM September 17, 2023...A thermal trough will bring northerly winds of 20 to 25 kts and gusts up to 30 kts this morning, building steep seas in waters south of Cape Blanco. Winds will decrease this evening and seas are expected to calm later tonight. The thermal trough is forecast to strengthen Monday, building steep wind-driven seas in all waters by Monday evening that will continue through at least midweek. Additionally, very steep and hazardous seas are expected in waters south of Cape Blanco starting Tuesday evening. Local areas of gale seas will be possible as well. A Gale Watch is in place from Tuesday at 5 PM through Thursday at 2 AM over areas that may experience these conditions. Appropriate warnings will be issued once there is more confidence in coverage and duration. -TAD && .FIRE WEATHER...Updated 300 AM PDT Sunday, September 17, 2023...An upper low will linger off the California coast today, resulting in continued southerly flow into the region. Isolated thunderstorms yesterday afternoon brought a total of 48 lightning strikes, focused over southwestern Siskiyou County. There remains enough elevated instability in this same area for some overnight showers/thunderstorms to occur before sunrise this morning. Confidence isn't high that this happens and chances remain less than 20%. Later this afternoon and evening, thunderstorm chances will spread across a broader area, and isolated thunderstorms are possible again in northern California, but but also areas from southern Josephine/Jackson counties east- northeastward across the Cascades and over to the East Side. This includes Ashland, Yreka, Klamath Falls, Alturas and Lakeview. Expect seasonable afternoon breezes today with recoveries expected to be moderate to locally poor over the ridges (inland of the immediate coast). East winds over the coastal ridges into the Kalmiopsis Wilderness are expected at 5 to 10 mph with gusts to 20 mph through this morning, then 10 to 15 mph with gusts to 25 mph tonight. A quick-moving upper trough will move into the Pacific Northwest Sunday night and across the area Monday. This will produce an uptick in afternoon west to northwest breezes, especially east of the Cascades. This will also begin a more noticeable cooling trend that will be reinforced by another quick-moving upper trough that swings through Tuesday. Expect light to moderate northeast winds across the coastal ridges Monday night but with moderate or better recoveries. Tuesday night, these northeast winds may trend higher with moderate northeast flow possible across the coastal ridges and into far western Siskiyou County. These incoming troughs push low pressure south of the region and bring more stable conditions under a west to northwest flow aloft. The upper level trough will likely linger over the region into Friday. As this trough initially moves in, expect a period of breezy to gusty northwest winds, strongest east of the Cascades, as the thermal trough at the surface strengthens Tuesday, becoming north to northeast Wednesday into Thursday, then backing to northwest again Friday. Humidities will also increase with the arrival of this trough, with a slight chance to chance of light showers over some portion of the area Wednesday into Thursday. Friday into Saturday, an eastward shift in the position of the trough could result in warmer temperatures, and drier humidities. /BR-y/DW && .MFR WATCHES/WARNINGS/ADVISORIES... OR...CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT this evening for PZZ356-376. Small Craft Advisory from 5 PM Monday to 5 PM PDT Tuesday for PZZ350-356-370-376. Gale Watch from Tuesday afternoon through late Wednesday night for PZZ356-376. && $$ MNF/TAD