####018006097#### FXUS66 KPDT 121552 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 852 AM PDT Sun May 12 2024 .MORNING UPDATE...Satellite imagery this morning shows clear skies across the forecast area, though a fire in central Klamath county did push smoke aloft across portions of Deschutes, Crook, and Grant counties. Today, an upper ridge over the area will bring another round of dry and warm conditions, then push east into ID/MT by this evening. However, west to northwest winds will increase through the Cascade gaps into the OR Columbia Basin this afternoon. Winds will be 15-25 mph with gusts up to 35 mph, and locally 40-45 in portions of the Kittitas valley this afternoon. Afternoon temperatures in the Lower Columbia Basin in WA and the Yakima valley will warm into the upper 80s to low 90s, with upper 70s to mid 80s across the rest of the lower elevations. Lawhorn/82 && .PREV DISCUSSION... /issued 224 AM PDT Sun May 12 2024/ SHORT TERM...Today through Tuesday...The upper level ridge over the region will move off to the east today as a low amplitude trough approaches from the west. This will bring the onset of a marine push in the afternoon with increasing westerly winds of 15-25 mph and gusts around 35 mph along the east slopes of the Cascades that push out into the Columbia Basin through the afternoon and evening. This will result in temperatures across the western portion of the forecast area being 4-8 degrees cooler on Sunday while the eastern portion remains unchanged from Saturday's highs. Winds will remain breezy Sunday night and then increase further on Monday with the trough passage boosting winds another 5-10 mph. This could bring wind speeds and or gusts close to advisory levels in portions of the COlumbia Basin and especially the Kittitas Valley. Precipitation looks to be limited to a few showers in the central and northern Washington Cascade crest. There is also a very low 5-10% chance of precipitation over the far eastern mountains in the Monday afternoon and overnight period. On Tuesday the trough moves into the northern Rockies and a ridge of high pressure over the eastern Pacific begins moving into the PacNW. This will bring a reduction of winds and maintain highs in the 70s to around 80 in the lower elevations and 60s in the mountains. LONG TERM...Wednesday through Sunday...The long term will be characterized by relatively benign weather. Temperatures will moderate back to near normal and precipitation will remain nill until chances slightly (<25%) towards the end of the period, but only in the higher peaks of the WA Cascades. All in all, a typical late spring pattern up ahead. Wednesday and Thursday models are in firm agreement with an upper level high pressure system parked off the coast of OR bringing mostly a northwest flow across the forecast area. Ensembles clusters are in agreement with the ridge with the main variance being in the amplitude. Regardless of this fact, dry and warm conditions will occur Wednesday and Thursday with over 90% of the raw ensembles showing the entirety of the Columbia Basin seeing temperatures in over 75 degrees as well as the Gorge, foothills of the Blues and Yakima/Kittitas Valleys. 40-60% show central and north central OR above 75 degrees as well as the John Dy Basin. Lastly, well over 90% of the ensembles show the remainder of the forecast region to be above 65 degrees with the highest peaks in the 50s. Thursday night through Sunday models show the upper level high pressure ridge begins to traverse southward ans an upper level shortwave makes it way into the PacNW. However, clusters show there to be a wide variance in the positioning and timing of the incoming shortwave. ECMWF brings it in faster and farther to the north of the area enhancing precipitation chances across the far northern Cascades. The GFS however, brings it in closer to Friday evening. With this shortwave, temperatures will cool slightly across the forecast area and will bring with it less than 15% probabilities of precipitation to the far north Cascades through Saturday increasing to 25% Sunday. However by Sunday models fall out of agreement with ECMWF suggesting a a continued trough while the GFS brings back another ridge. Another thing of note with the incoming shortwave will be the increase in winds, especially through the Cascades Gaps as the shortwave causes the cross Cascade pressure gradient to increase with the more westerly upper level flow. Highest winds are expected Thursday night with the initial passage of the shortwave with with 50-70% probabilities of sustained winds up to 25 mph, decreasing in speed slightly each day thereafter. EFI continues to show the region to be under climatological normal temperatures with over 60% of the ensembles showing temperatures to average 70-75 degrees across the majority of the region with a few isolated locations in the Basin seeing low 80s. Bennese/90 AVIATION...12Z TAFs...VFR with mostly clear skies for all TAF sites through the forecast period. Winds will be the only interest as they will be terrain driven and generally less than 10kt increasing to 13- 15 kts with gusts to 22kts around 18-20Z for all sites except PSC. Bennese/90 && .PRELIMINARY POINT TEMPS/POPS... PDT 82 52 75 47 / 0 0 0 0 ALW 84 56 78 51 / 0 0 0 0 PSC 90 57 82 52 / 0 0 0 0 YKM 86 51 79 45 / 0 0 0 0 HRI 86 55 80 50 / 0 0 0 0 ELN 80 54 71 47 / 0 0 0 0 RDM 77 44 74 40 / 0 0 0 0 LGD 79 47 73 44 / 0 0 0 0 GCD 79 46 75 42 / 0 0 0 0 DLS 82 54 74 50 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ MORNING UPDATE...82 SHORT TERM...91 LONG TERM....90 AVIATION...90