


Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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134 FXUS66 KPDT 150543 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 943 PM PST Fri Feb 14 2025 .Updated Aviation Discussion. .AVIATION...06Z TAFS...VFR conditions currently experienced at all sites, with most sites degrading to either MVFR or IFR toward the end of the period as a result of an incoming weather system. The only exception will be for KRDM/KBDN, which should stay VFR through the period. Light snow will be impacting the remaining sites during the mid-to late afternoon as ceilings drop to 1.5-3kft with visibilities of 2-4SM. IFR conditions are expected at KALW toward the end of the period as visibilities drop to 2SM. Elsewhere (KDLS/KPDT/KYKM/KPSC) conditions will drop to MVFR with visibilities of 3-4SM and ceilings of 1.5-2.5kft. Winds will stay light and below 10 kts for all sites through the period. 75 && .PREV DISCUSSION... /issued 304 PM PST Fri Feb 14 2025/ SHORT TERM...This afternoon through Sunday night...A flattening shortwave trough is exiting the Pacific Northwest to the east this afternoon, leaving a northwesterly flow aloft and some isolated to scattered upslope snow showers across the Blue Mountains and their adjoining foothills. Winter Weather Advisories remain in effect for the Blue Mountains through 10PM this evening, where confidence is high (70-90%) in an additional 1-3" of snow accumulation beneath snow showers. Elsewhere, cancelled the winter weather products for the foothills of the northern Blue Mountains of OR/WA early since accumulating snowfall tapered off late this morning; confidence is high (80%) that additional accumulations in snow showers will be light at 0.5" or less. This evening through Saturday morning, an upper-level shortwave ridge will push east over the Pacific Northwest, bringing upslope snow to an end. The break in precipitation will be brief as the next upper-level low and attendant weak frontal system is slated to arrive by Saturday afternoon. While the warm frontal boundary looks weak with a shallow, weak warm nose aloft, this will pose some potential for light freezing rain or mixed wintry precipitation (rain/snow/freezing rain) for sheltered valleys along the east slope of the OR/WA Cascades, the Columbia River Gorge, lower Columbia Basin, and Blue Mountain foothills. Probabilities are low-medium (20-50%) in accumulating freezing rain (0.01" or greater) for the aforementioned areas Saturday night through Sunday. Additionally, there is a medium-high probability (40-80%) in measurable lowland snow in Washington, with a low-medium probability (20-60%) for the lowlands of Oregon. Of note, there is up to a 30% probability of advisory-level snowfall (2" or more) for the lowlands of OR/WA Saturday afternoon through Sunday night. Have held off on issuing any winter weather products for the lower elevations due to medium-high (50-70%) confidence in forecast ice and snow (below the required 80% threshold). Snow in the mountains of eastern Oregon and eastern Washington will likely reach advisory levels between Saturday afternoon and Monday morning, with the best chances for the OR/WA Cascade crest (70-90%) and northern Blue Mountains. Probabilities of warning- level snow are below 80%, so opted to issue advisories for the Cascades. Held off on issuing for the Blue Mountains since existing highlights are in effect. Plunkett/86 LONG TERM...Monday through Friday...An active weather pattern is in store for the region through the extended forecast as a series of shortwave troughs bring periods of mountain snow and potentially a mix of precipitation types in the lowlands. Ensemble cluster guidance is in great agreement Monday of a shortwave trough swinging across the PacNW and exiting southeast of the region with a transitory ridge moving inland Tuesday. While snow levels are expected to be 2.5kft to 4kft across the forecast area, the cooler temperatures Monday morning will result in a rain/snow mix in portions of the WA Columbia Basin. As the day progresses and temperatures warm-up in the lowlands, any precipitation will fall as light rain into the early evening hours (confidence 60-70%). Light to moderate snowfall accumulations between 5 to 8 inches will develop across the OR Cascades and the northern Blues through Monday, with snowfall amounts up to 2 inches along the WA Cascade crest and higher ridges of the eastern mountains (confidence 60-80%). Drier conditions will develop into Tuesday as the ridge pushes inland, however, northwest flow aloft on the lee side of the ridge will continue to produce light snow across the mountains through Tuesday night. Wednesday through Thursday, disagreement amongst the ensemble cluster guidance greatly increases on timing and strength of an incoming shortwave trough that will flatten the ridge Wednesday and exit to the southeast sometime late Thursday. That said, confidence is mod-high (60-80%) in area-wide precipitation chances returning to the forecast area with another round of light to moderate snow chances in the mountain zones. As for the lowlands, the cluster solutions with the stronger shortwave trough will result in higher chances of precip and precip amounts, while the lower 500mb heights will result in snow levels at or below the surface. At this time, confidence is low (20-30%) in precipitation type for the lower elevations, which has translated to chances of a rain/snow mix in the forecast. Confidence in timing of precipitation tapering off is also low (20-30%) as well, as cluster solutions are split between the shortwave exiting in the morning, afternoon, or evening Thursday. Behind the shortwave exit, guidance is in good agreement in a ridge building back into the PacNW with dry conditions Friday, though one cluster solution (25% of members) keeps light snow chances across the mountains. Lawhorn/82 && .PRELIMINARY POINT TEMPS/POPS... PDT 22 38 27 41 / 30 30 80 90 ALW 24 36 30 38 / 40 20 90 90 PSC 18 35 29 39 / 10 20 70 70 YKM 20 36 27 38 / 0 30 70 50 HRI 20 37 29 41 / 10 30 70 80 ELN 22 36 26 38 / 0 40 80 60 RDM 15 41 27 46 / 0 20 30 50 LGD 24 36 29 40 / 50 30 90 90 GCD 19 38 29 43 / 30 30 80 90 DLS 29 41 32 43 / 10 40 80 90 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Winter Weather Advisory from 10 PM Saturday to 10 AM PST Monday for ORZ509. WA...Winter Weather Advisory from 4 PM Saturday to 10 AM PST Monday for WAZ522. Winter Weather Advisory from 4 PM Saturday to 4 AM PST Monday for WAZ523. && $$ SHORT TERM...86 LONG TERM....82 AVIATION...75