Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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705 FXUS66 KPDT 221722 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 1022 AM PDT Sat Jun 22 2024 .AVIATION...18Z TAFS...VFR conditions remain for this period. All sites currently have some clouds within their areas. An incoming system will be increasing winds for KDLS/KRDM/KBDN at 12-20kts having wind gusts around 20-25kts. Feaster/97 && .PREV DISCUSSION... /issued 205 AM PDT Sat Jun 22 2024/ SHORT TERM...Today through Monday night...A Fire Weather Watch in effect for Sunday afternoon and evening for the Lower Columbia Basin zones (fire zones WA691 and OR641) was issued yesterday. A Wind Advisory for the Kittitas Valley in effect from 4 AM to midnight on Sunday will be issued for the morning package. A strong inverted thermal trough at the surface currently extends across CA/NV and into eastern OR/WA, and this has resulted in above average temperatures. There has been little relief from yesterday`s hot summer weather, as overnight temperatures have only dipped into the 50s and 60s for most of the forecast area. Today`s highs in the mid 80s to upper 90s are about 15 degrees above seasonal average. It would have been much warmer if not for the westerly flow aloft keeping the pressure thickness from climbing and the high level clouds over the area. Based on the NBM, there is a chance (around 30-50%) that a few locations in the Lower Columbia Basin and the John Day Basin near Monument and Spray will reach 100 degrees. Cool marine air due to the onshore flow and the thermal trough over eastern WA/OR will cause winds to increase in the eastern CR Gorge and the Cascade gaps tonight. The marine air will deepen on Sunday when a shortwave trough traverses across northern WA. Forecast soundings near Seattle indicate the marine layer deepening to a depth of 6k feet which increases the confidence to around 80% that the marine push will be strong and deep enough to cause sustained winds around 30 mph and gusts 45-50 mph in the Kittitas Valley and locally in the CR Gorge--mainly near Maryhill and Rufus. Will issue the wind advisory for the Kittitas Valley, and one may be needed for the Gorge if the very windy conditions are expected to cover a larger area. Dry air will accompany the shortwave and surface cold front. Water vapor shows significant darkening along the bottom of the trough, and models have consistently shown H7 RHs in the single digits. The marine push will cause RHs to increase into the upper 20s to lower 30s along the Cascade gaps. However, the Columbia Basin and the Blue Mtn Foothills will observe RHs in the teens as the dry air mixes down with the front (confidence 80%). The low RHs combined with WSW winds 20-30 mph gusting to 40 mph warrants a fire weather watch. Any precipitation associated with the shortwave will be light showers in the far northwest corner of the CWA north of Cle Elum. Gradients will relax Sunday night and the flow will become slightly more anticyclonic with weak ridging on Monday. Temperatures will be closer to seasonal average and winds will be 15 mph or less. Skies will be mostly clear Monday and Monday night. Wister/85 LONG TERM...Tuesday through Saturday...The ridge axis begins to sweep across the forecast area at the onset of the forecast period. Temperatures will remain warm on Tuesday, with values around 5-10 degrees above normal. Aside from keeping warm and dry conditions across the area, this ridge axis will also briefly produce an opportunity for gusty winds. Areas of the Columbia River Gorge and south into Central Oregon will be favored for these stronger winds on Tuesday afternoon and evening with a 30-40% chance for gusts to 25 mph. Winds will see a brief reprieve Wednesday morning. Building southwest flow and an associated approaching low pressure system will produce additional gusty wind, with more coverage expected. While much of the area will see at least a slight chance (10-25%) for gusts to 25 mph, areas along the Washington/Oregon border, into the Columbia Basin, and south into Central Oregon remain the areas anticipated to see the strongest wind. At these locations, there will be a moderate to high chance (70-90%) for gusts to 25 mph, with the Columbia River Gorge area seeing a 40-60% chance for gusts of 30- 35 mph. On a more limited note, this approaching system will produce some shower activity, mainly over the Cascade Mountains. Temperatures will see a few degrees of cooling but will still see around 5 degrees above normal values on Wednesday. While some model variation regarding the path and intensity of the low pressure is present on Wednesday, the differences become more noticeable on Thursday with some solutions keeping the area of low pressure off the Pacific Coast, and others pushing it into the PacNW. As anticipated, the cluster analysis also shows variation on the departure of the ridge and the arrival of the low pressure system. Utilizing the NBM, further cooling of temperatures is favored on Thursday when values drop to around 5 degrees below normal. The area of low pressure will work its way through the region Thursday and Friday with mountain showers. Northwest flow builds over the region on Friday with a few degrees of warming and weakened shower presence. High pressure will arrive into Saturday, allowing temperatures to rise to a few degrees above normal, and help to further reduce shower activity. Branham/76 && .PRELIMINARY POINT TEMPS/POPS... PDT 93 59 81 49 / 0 0 0 0 ALW 96 63 86 52 / 0 0 0 0 PSC 98 64 88 53 / 0 0 0 0 YKM 96 56 83 48 / 0 0 0 0 HRI 98 63 85 53 / 0 0 0 0 ELN 92 56 75 48 / 0 0 0 0 RDM 91 51 83 43 / 0 0 0 0 LGD 91 56 83 48 / 0 0 0 0 GCD 95 55 89 48 / 0 0 0 0 DLS 92 60 78 53 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Fire Weather Watch from Sunday afternoon through Sunday evening for ORZ641. WA...Fire Weather Watch from Sunday afternoon through Sunday evening for WAZ691. Wind Advisory from 5 AM Sunday to midnight PDT Sunday night for WAZ026. && $$ SHORT TERM...85 LONG TERM....76 AVIATION...97