Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
117 FXUS66 KPDT 090552 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 1052 PM PDT Tue Jul 8 2025 .AVIATION...06Z TAFs...A pair of weather systems will track over the region through Wednesday, inducing periods of breezy to windy conditions for all TAF sites. Isolated high-based showers and thunderstorms across south-central Washington and northeast Oregon have a very low (<30% chance) of impacting DLS/YKM/PSC/ALW/PDT through 09Z Wednesday. Plunkett/86 && .PREV DISCUSSION... /issued 141 PM PDT Tue Jul 8 2025/ .SHORT TERM...Tonight through Thursday...Satellite imagery this afternoon shows mostly clear conditions across the region, though cumulus fields are beginning to develop along the higher terrain of central and eastern OR. Upper level ridging over the PacNW will begin to break down later this evening as a developing trough offshore begins to move inland. However, the influence of the upper ridge will continue to be felt across the region today, as high temperatures across the Columbia Basin increase into the lower 100s, with widespread mid to upper 90s elsewhere. Ahead of the trough, southwest flow has developed across the PacNW, leading to increasing instability across central and eastern OR this afternoon. Isolated to widely scattered thunderstorms (15-20% chance) developing in these areas throughout the afternoon and evening will be able to tap into that instability, but also tap into the strong low to mid level lapse rates. All that said, shear aloft doesn`t look to favor maintaining storms, so gusty outflow winds from a collapsing updraft are expected. Thunderstorm activity is expected to wane tonight, however, an HREF member or two do depict a few storms developing and moving along the Blue Mountain foothills tonight, but confidence is very low (10%) in these storms developing. Otherwise, breezy winds will begin to develop through the Cascade Gaps as the cross Cascade pressure gradient tightens. Wednesday, the upper trough and a dry cold front will move across the PacNW bringing two fire weather concerns: strong winds and another round of isolated thunderstorms. Persistent instability across eastern OR in tandem with some divergence aloft will allow for isolated thunderstorms (~15% chance) to develop across southern and eastern portions of Grant county into southern Union and Wallowa counties tomorrow afternoon and evening. As for winds, the cold front passage tomorrow afternoon will result in sustained winds of 25-35 mph with gusts up to 45 mph developing through the eastern Gorge and Kittitas valley, with sustained winds 20-30 mph and gusts up to 40 mph across the Columbia Basin and portions of north central OR. Winds will generally be 15-25 mph with gusts 25-35 mph elsewhere in the lower elevations. The cold front boundary will also produce cooler temperatures tomorrow into Thursday, which will help increase afternoon RHs above critical thresholds tomorrow. That said, the strength of the winds tomorrow will overcome the impacts from higher RHs, necessitating the need of a Red Flag Warning for the Columbia Basin tomorrow afternoon and evening. By Thursday afternoon the upper trough will have moved east of the region, leaving behind a cooler airmass with locally breezy conditions through the Cascade Gaps. By the evening hours, a transient upper level ridge will slide across the PacNW, with a more broad upper ridge beginning to develop in the northeast Pacific. Lawhorn/82 && .LONG TERM...Friday through Tuesday...Ensemble cluster guidance in great agreement through the extended forecast that upper level riding will build over the northeast Pacific, with the PacNW coming under the influence of the upper ridge (confidence 60-70%). Flow aloft will waver from a weak zonal flow into northwest flow aloft early next week. Temperatures will be increasing Friday into the weekend, with a slight cool off into early next week with northwest flow developing. Breezy winds will develop through the Cascade gaps each day as well, but as flow aloft turns more northwesterly, the Kittitas Valley and gaps through the WA Cascades will see breezy to locally gusty conditions (50-70%). Otherwise, mod-high confidence (60-80%) that the upper ridge will suppress storm activity across the region through early next week. Lawhorn/82 && .PRELIMINARY POINT TEMPS/POPS... PDT 64 91 59 86 / 20 0 0 0 ALW 68 92 63 85 / 20 0 0 0 PSC 64 95 60 89 / 20 0 10 0 YKM 62 89 58 87 / 20 0 10 0 HRI 66 93 61 89 / 20 0 0 0 ELN 64 82 57 82 / 10 10 10 0 RDM 52 86 51 83 / 20 0 0 0 LGD 61 87 57 81 / 20 10 10 0 GCD 56 89 54 84 / 20 20 20 0 DLS 65 84 61 84 / 20 0 10 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Red Flag Warning from 11 AM to 10 PM PDT Wednesday for ORZ691. Red Flag Warning from 2 PM to 11 PM PDT Wednesday for ORZ698. WA...Red Flag Warning from 11 AM to 10 PM PDT Wednesday for WAZ691. && $$ SHORT TERM...82 LONG TERM....82 AVIATION...86