Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
907 FXUS66 KPDT 030521 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 1021 PM PDT Sat Aug 2 2025 Updated Aviation Discussion .AVIATION...06z TAFs...Expecting mostly VFR conditions through the period, however BDN/RDM will once again see a chance of showers and thunderstorms starting late Sunday afternoon and lasting through the early evening hours. These storms may bring periods of sub-VFR conditions (40-50% confidence). Otherwise, all other sites will see clouds gradually building overnight tonight, becoming sct-bkn around 10-15 kft by late Sunday morning. Winds will generally be terrain-driven less than 12 kts, except for DLS which will see gusts up to 25 kts at times, and BDN/RDM could see stronger gusts around the vicinity of thunderstorms. Evans/74 && PREV DISCUSSION... /issued 128 PM PDT Sat Aug 2 2025/ DISCUSSION...An active weather pattern accompanied by showers and thunderstorms as well as locally breezy winds is forecast this weekend into Monday as an offshore upper-level trough swings onshore Sunday through Monday. There is significantly more uncertainty in the 500-hPa pattern, and forecast details, by the middle to end of next week in the wake of this first trough. However, ensemble NWP is trending towards a broad troughing pattern with some potential (10-40%) for precipitation for the entire forecast area; highest chances will be over the Washington Cascades, followed by the Oregon Cascades and northern Blue Mountains. Today, isolated thunderstorms have developed across the Blue Mountains. A mix of wet and dry storms is forecast, with no fire weather products in effect due to insufficient confidence in abundant lightning. Elsewhere, there is medium (40%) confidence in small pockets of wind/rh overlap meeting Red Flag conditions in the eastern Columbia River Gorge and western reaches of the lower Columbia Basin this afternoon and Sunday afternoon. Looking ahead to tonight, NWP guidance shows a weak shortwave tracking over eastern Oregon and south-central Washington, embedded within a broader region of synoptic-scale forcing associated with the aforementioned upper-level trough. Coupled with pockets of negative mid-level (700-500mb) theta-e lapse rates and ample mid-level moisture (RH of 70-100%), this may induce isolated nocturnal shower/thunderstorms tonight/Sunday morning over central Oregon, eastern mountains, Blue Mountain foothills into the lower Columbia Basin. Confidence in occurrence is currently medium (40-60%), highest across the Ochocos, southern Blue Mountains, and adjacent foothills. Sunday, there is high confidence (80%) in scattered showers and thunderstorms across central Oregon and the Blue Mountains. Activity will be more isolated across the foothills and Columbia Basin. Isolated dry thunderstorms are forecast with most storms remaining wet (0.10" of precipitation or greater), thus no fire weather products have been issued despite anticipated lightning. Forecast CAPE of 500-1000 J/kg, effective shear of 25-35 kts, and inverted-v soundings should facilitate a marginal threat of severe (50 kts or greater) outflow winds and small to marginally severe (1-inch diameter) hail across portions of central and eastern Oregon. A brief lull in active weather is anticipated Tuesday, followed by a return to active weather Wednesday through Friday. While the most likely outcome keeps the bulk of the precipitation from the Washington Cascades north through southern Canada, a more interesting alternate scenario is present in ensemble solutions. More specifically, there is a low potential (10% or less) for an early-season, inland-penetrating atmospheric river coupled with sufficient synoptic forcing to facilitate a noteworthy precipitation event for inland areas. While ensemble-mean PWATs of 120-180% of normal are advertised area-wide across eastern Oregon and eastern Washington, significant ensemble spread is present with regard to timing of said moisture transport into the region. Will note the 00Z Aug 7 to 00Z Aug 8 ECMWF EFI shift of tails is positive for the lower Columbia Basin, Blue Mountain foothills, and northern Blue Mountains. That said, it is small (0-1), indicating the tail of the QPF distribution is forecasting an anomalous event relative to model re-forecasts. && .PRELIMINARY POINT TEMPS/POPS... PDT 60 88 59 83 / 0 20 40 30 ALW 64 89 63 82 / 0 20 30 30 PSC 60 92 59 86 / 0 20 20 20 YKM 59 90 59 86 / 0 0 10 10 HRI 62 91 60 85 / 0 20 30 20 ELN 59 86 57 80 / 0 0 0 10 RDM 52 85 48 81 / 20 20 30 10 LGD 56 85 55 78 / 10 30 60 40 GCD 57 87 54 80 / 20 60 60 30 DLS 62 82 60 79 / 0 0 10 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...86 LONG TERM....86 AVIATION...74