Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
473 FXUS66 KPDT 150553 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 953 PM PST Thu Nov 14 2024 .Updated Aviation Discussion. .AVIATION...06Z TAFS...VFR conditions currently at all sites, which will stay the course through the period. The only exceptions will be over Central Oregon (KRDM/KBDN) and along the Blue Mountain foothills (KALW/KPDT) as ceilings are expected to drop to OVC030 and OVC015 respectively through the overnight period. Breezy afternoon conditions are anticipated at KDLS with gusts of up to 23 kts possible. All other sites will experience winds of 10 kts or less through the period. Ceilings look to lift toward the end of the period across all sites. 75 && .PREV DISCUSSION... /issued 211 PM PST Thu Nov 14 2024/ SHORT TERM...Today through Saturday...A broad upper-level trough continues to move into the PacNW this afternoon, bringing with it cooler air and breezy winds ahead of its axis. Winds have been a bit more robust than what guidance initially suggested, especially in the lower Columbia Basin around Tri-Cities. Expecting that to trend downward heading into tonight as pressure gradients even out. As this system moves in, however, SW flow aloft ahead of its axis will allow for some orographic precip across the eastern mountains of Oregon. Hi-res guidance over the last 24 hours have shifted their tune quite a bit, initially showing a mostly dry forecast, while now showing a band of snow enveloping an area extending from Grant County up through the Wallowas tonight through late Friday morning. Models hint at a vort max potentially assisting in shower development over the mountains, but should note that each individual model is highly variable in terms of how heavy of snowfall we get with this system. Opted to adjust amounts higher than the initial WPC forecast, but amounts overall still look to fall below Advisory thresholds. Still, those in the aforementioned areas, particularly in the Bear Valley, Southern Blues (namely around Ukiah), and I-84 through Meacham should expect a couple of inches of snow overnight tonight heading into tomorrow. Maybe some light snow in the Wallowa Valley as well, but confidence is on the lower end. Should note that NBM probabilistic guidance in particular isn`t exactly enthusiastic about snow tonight outside of the crests of the Blues and Strawberries. Colder, drier air then filters in behind the trough heading into Friday evening as the flow aloft shifts more northerly. Expecting relatively dry conditions Friday night through late Saturday afternoon, however high temps will struggle to reach the 50s, even across our lowest elevations both days. The next system of concern will arrive late Saturday night into Sunday, where more widespread, heavier precip is expected to occur. Evans/74 LONG TERM...Sunday through Thursday...West to southwesterly flow ahead of the next trough followed by the trough moving across the region on Sunday into Sunday night will bring precipitation to the Pacific Northwest into Monday. Snow levels will initially be fairly high...ranging from over 5000 to 7000 feet in most locations to 3000- 4000 feet over far eastern Oregon. However, by Monday morning, snow levels will drop to 2000-2500 feet everywhere. Beyond Monday into Tuesday, precipitation should end as ridging builds in behind the departing trough. The ridge looks to get quite strong by mid to late week, but before then, there is some uncertainty. The QPF with this system is upwards of an inch in the higher elevations of the Blue Mountains and could approach 2 inches of the higher elevations of the Washington Cascades. At the lower elevations 0.25 to 0.5 inches is possible in many areas except central Oregon and the Columbia Basin. Based on these values, some headlines for snow may be needed for northern Blue Mountains or Washington Cascades, depending on how things develop by Sunday night. The ECMWF EFI has 0.7 to 0.8 for QPF across the Cascades on Sunday. The ECMWF has a much stronger trough in the Great Basin/Four Corners area around Tuesday and has a stronger ridge behind it, while the GFS is weaker. The ensemble clusters only have about 25% support for this solution. The drier weather pattern that would build in mid to late week would still possibly allow for some precipitation, mainly over the Washington Cascades, and depending on the ultimate position and strength of the ridge we could be looking at our first bout of stratus and/or fog, especially over the favored valley locations. Winds will be breezy on Sunday into Sunday night as the trough moves across the area, with gusts generally in the 25 to 35 mph range. NBM probabilities of wind gusts to 39 mph are generally 50 to 80 percent, mainly across the Columbia Basin, Simcoe Highlands and Foothills of the Blue Mountains. High temperatures will start off the period above normal on Sunday, but end the period several degrees below normal. && .PRELIMINARY POINT TEMPS/POPS... PDT 34 45 27 46 / 20 20 10 0 ALW 37 46 30 48 / 20 30 20 0 PSC 38 51 30 48 / 10 10 0 10 YKM 30 51 24 43 / 10 0 0 20 HRI 37 51 29 49 / 10 10 0 10 ELN 31 47 25 43 / 10 10 0 20 RDM 29 42 21 43 / 20 10 0 10 LGD 33 40 26 42 / 60 60 30 0 GCD 32 40 23 41 / 90 50 30 0 DLS 37 52 31 48 / 10 10 0 30 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...74 LONG TERM....77 AVIATION...75