FXUS66 KPQR 232214 AFDPQR Area Forecast Discussion National Weather Service Portland OR 314 PM PDT Wed Oct 23 2024 .SYNOPSIS...Cumulus over the area with gusty winds aloft. Frost and freezing temperatures tonight. Will see sunny skies through Thursday before another front moves in overnight. Gusty offshore winds on Friday morning. Heavy rain over the weekend with gusty southerly winds. Uncertainty in the intensity of winds on Saturday. Rain persists through the next week. && .SHORT TERM...Now through Friday Night...A more convective atmosphere is present today as the main front that brought stratus and light showers has shifted eastward. Behind it, cumulus and gusty winds aloft are present. These partly cloudy skies will play a role in the weather tonight as radiational cooling combined with cold air behind the front will cause surface temperatures to drop. Looking at widespread lows in the mid to lower 30s, with around a 60-80% chance for temperatures around 32 degrees F or less tonight. These areas will largely be in the central to southern Willamette Valley, ridgetops and protected valleys of the Coast Range and areas from the Cascade Foothills eastward. Even colder temperatures possible within the Upper Hood River Valley where the probability for low temperatures less than 30 degrees F is near 100%. With light winds at the surface and a dry layer, frost is going to be likely overnight and thus, a frost advisory in effect for much of the lowlands. In addition, these cold temperatures within the Hood River Valley have prompted a Freeze Warning which is associated with the potential for outdoor pipe damage and vegetation kills. Thursday will be cloudy, but dry once again as zonal flow takes over. No real weather to speak of on Thursday until the overnight hours. The big weather player this weekend will be a deepening low pressure system over the northeast Pacific. This low is moving northeastward over the Alaska Panhandle Friday morning, but the leading edge of this low will push a secondary front and mesoscale low inland. At 850 mb, winds are southerly and temperatures are around 10 degrees C. These warm temperatures and pressure gradient at the surface will cause offshore winds to increase significantly. Between North Bend, OR and Spokane, WA, the pressure gradient is around -11 mb. These winds will bring gusts up to 40 mph in the Columbia River Gorge, and up to 30 mph in the Portland-Vancouver Metro Area out to Beaverton. These winds will be short-lived and will ease in the afternoon. The mesoscale low will be looped back into this parent low late Friday. -Muessle .LONG TERM...Saturday through Wednesday...On Saturday, the shortwave will be fully absorbed and winds will become southerly. There is a great deal of uncertainty in the path of this low and associated systems which is making the forecast very difficult. Recent model runs have showed the low slowing which could either a) cause it to fill and move north, or b) deepen and arrive stronger. The track of the low will determine the strength of the winds. Decided to increase winds, especially along the beaches and headlands, as the overall track is trending towards the more robust direction. Nudged towards the 90th percentile of the NBM to account for these winds. Inland locations too could see amplified gusts, especially through the Willamette Valley, but at this point, confidence remains too low to modify. Rain will also be a big piece of the forecasting pie this weekend. Strong, moist flow will push inland bringing heavy rain to the Coast Range on Saturday morning, increasing overnight as another surge moves in. This rain continues through Sunday with nearly a 75% chance of 0.5 inch, and a 50% chance of 0.75 inch by early Monday morning. For those along the coast, the NBM is showing nearly a 60% chance of 1 inch or more on Sunday. This rain will ease through mid-week. -Muessle && .AVIATION...Generally VFR conditions are in place across the region likely persisting through the rest of the afternoon and evening hours. That said, radar does indicated a few isolated showers around and east of the coast range so a 10-15% for showers will exist until 01-02z; little to no impacts to prevailing conditions. Headed through tonight into sunrise Thursday clearing skies, ample surface moisture, and light winds will facilitate patchy fog formation throughout the Willamette Valley - the best chances for fog remain at KHIO/KUAO southward and after 10-12z. Winds remain fairly light at all sites, generally less than 10 knots through the TAF period. PDX APPROACHES...Generally VFR conditions continue although brief periods of MVFR are possible until sunset. After this point we'll have to watch for possible(20-40%) degraded conditions due to fog/low stratus towards sunrise but compared to other portions of the region confidence in timing/impacts locally are still low at this time. -Schuldt && .MARINE...Tonight through early Friday an area of high pressure will continue to influence the region resulting in fairly light winds and benign seas through Friday morning. Northerly winds are expected to strengthen each afternoon and evening, especially south of Cape Foulweather, but will generally remain below 20-22 kt. On Friday a strong surface low pressure is expected to develop over the eastern Pacific with models pushing it north/northeastward towards Vancouver Island late Friday into early Saturday. This will result in an rapid increase southerly winds and building seas across all waters as the aforementioned feature progresses. The latest guidance indicates a 60%-70% probability for for Gale Force southerly wind gusts during this time for the outer waters however some uncertainty remains as to the overall timing and location of the low. That said the 12z models and their ensembles remain in decent agreement with past runs leading to increased confidence in Gale conditions. Thus, a Gale Watch was issued for the outer water from 5pm Friday to 5am Saturday morning. If current forecast trends continue it may need to be extended to the inner waters as well during this same period. In addition to the elevated winds, seas will also build towards the low to mid teens by late this week/weekend. The broad upper-level trough responsible for steering the first system overhead will then settle across the region over the weekend into early next week. This will bring a return to north/northwesterly winds, which will remain elevated, but will likely not result in Gale Force conditions. Winds and seas will slowly subside, but expect seas to remain in the 9 to 12 ft range through the start of next week. -Schuldt/42 && .PQR WATCHES/WARNINGS/ADVISORIES... OR...Frost Advisory from midnight tonight to 10 AM PDT Thursday for ORZ104>107-109-114>118-123>125. Freeze Warning from midnight tonight to 10 AM PDT Thursday for ORZ121. WA...Frost Advisory from midnight tonight to 10 AM PDT Thursday for WAZ203>205-208. PZ...Gale Watch from Friday afternoon through late Friday night for PZZ271>273. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland