Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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611 FXUS66 KPDT 192342 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 442 PM PDT Thu Sep 19 2024 .AVIATION...00Z TAFs...VFR conditions forecast for all sites through the TAF period. Southerly drainage winds overnight in central Oregon may push smoke/haze from area wildfires across BDN/RDM, but confidence in sub-6SM VSBYs and/or an opaque smoke layer is low (<30%). Otherwise, expecting cloud cover to consist of FEW-SCT250 for TAF sites. Sustained winds of 12 kts or less with higher afternoon/evening gusts, except for DLS. Plunkett/86 && .PREV DISCUSSION... /issued 201 PM PDT Thu Sep 19 2024/ SHORT TERM...Tonight through Saturday night...Overall, a quiet period of weather is in store. Low pressure off of the central California coast will gradually move south and eastward through Friday. The trough associated with this low will keep northwest flow over the Pacific Northwest. As the low moves further inland, some ridging will build in for Saturday, with a weak trough approaching Saturday night. There could be a passing shower over the higher terrain of the Cascades later tonight or toward Friday morning, but probabilities are low (<20%). Any showers received there are the only precipitation chances across the area through Saturday night. Breezy winds have been occurring today in the normally affected spots...the Kittitas Valley, Simcoe Highlands, portions of the Columbia Basin, with gusts generally to around 30 mph. These gusts are expected again on Friday in the northwest flow, though guidance suggests they will be possibly less. NBM probabilities of gusts >=39 mph are 50 to 70 percent in the Kittitas Valley and much less elsewhere...generally 30 to 40 percent with some isolated 50 percent values in the Columbia Basin and Simcoe Highlands. Low temperatures Saturday morning will be chilly in some of the higher elevations and elevated valleys. Right now, temperatures will be just above to right around freezing but will have to see what future guidance does and where to determine if any freeze warnings are necessary. LONG TERM...Sunday through Thursday... Bottom Line Up Front 1. WA Cascade rain, dry conditions elsewhere 2. Breezy Cascade Gaps 3. At or near normal temperatures Models show the beginning of the period to be under dry westerly flow as the upper level low continues to traverse to the south and another begins to push in from the northwest. As the trough to the northeast Sunday, upper level flow will turn slightly northwest and bring in light precipitation to the WA Cascades. Not only will this shift bring light rain, winds will also increase slightly through the wind prone areas of the Cascade Gaps as well as allow for temperatures to remain at or near normal through the period. However, models do become a bit chaotic around days 6 and 7 and are out of sync as to whether we will be under a tough or a ridge. Models show an upper level trough beginning to slide down the Canadian coast and towards the PacNW with a ridge trying to undercut it. Regardless, the leading edge of the system will bring some precipitation to the crests of the WA Cascades. 20-40% of the raw ensembles show only 0.3-0.5 inches of rain likely as the system crosses over the Cascades. Once the system passes over, dry conditions across the entire CWA are expected as the ridge undercuts the trough and moves over the area. With the leading edge of the system pushing across the region, surface pressure gradients tighten ever so slightly allowing for slightly breezy conditions through the Cascade Gaps. However, only 20-30% raw ensembles are showing sustained winds of 20 mph or greater. As the flow shifts to southwest flow under the ridge, diurnal winds through the Gaps will return with typical breezy conditions of less than 10 mph will return. Lastly, EFI shows temperatures to continue to be at or near normal through the forecast period. NBM shows at the beginning of the period to be in the mid to upper 70s across much of the lower elevations with so isolated 80s in the Basin and Gorge. As the upper level ridge moves overhead, NBM shows temperatures to begin to hedge more towards the upper 70s to low 80s with the Columbia Basin seeing mid 80s and 70-80% of the raw ensembles are in agreement. Looks like we will see a brief warm up again next week. Enjoy it while it lasts. Bennese/90 && .PRELIMINARY POINT TEMPS/POPS... PDT 46 69 41 70 / 0 0 0 0 ALW 51 72 45 73 / 0 0 0 0 PSC 52 75 46 74 / 0 0 0 0 YKM 44 75 41 75 / 0 0 0 0 HRI 51 74 44 74 / 0 0 0 0 ELN 49 72 43 77 / 0 0 0 0 RDM 40 72 36 72 / 0 0 0 0 LGD 43 69 40 71 / 0 0 0 0 GCD 42 71 38 72 / 0 0 0 0 DLS 52 72 48 79 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...77 LONG TERM....90 AVIATION...86