Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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742 FXUS66 KPDT 042147 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 247 PM PDT Tue Jun 4 2024 .SHORT TERM...Tonight through Thursday...Satellite imagery this afternoon shows mostly cloudy skies across the forecast area, with impressive gravity wave cloud streaks area wide. However, area radar shows little returns across the forecast area, except for light shower activity mostly confined to the central WA Cascades. Currently, pressure gradients across eastern WA/OR have tightened behind the cold front passage earlier today. With the shortwave currently passing through WA, the pressure gradients will remain tightened through the evening, resulting in a continuation of breezy winds across the lower elevations and Simcoe Highlands. While much of the lower elevations will have seen winds between 15-25mph with gusts to around 35mph, some exposed ridges and the Hanford area have had stronger 850mb winds up to 45mph and sustained winds of 25-30mph mix down this afternoon. The breezy winds and shower activity will continue through this evening, but will diminish overnight as the shortwave exits into western MT. By tomorrow morning, an upper level ridge of high pressure in the Desert Southwest will build into the PacNW and continue to build over the western CONUS through the late week. This will result in dry conditions and light winds across the forecast area Wednesday and Thursday. Not only that, but temperatures will be on the increase as well, with Thursday afternoon temperatures warming into the mid to upper 80s in the lower elevations, and mid 60s to 70s in the mountains. While conditions are expected to remain dry through the middle of the week, deterministic guidance, and even their ensemble counterparts, have been showing a signal for isolated thunderstorms to develop across southern and southeastern OR by Thursday afternoon. While confidence is low (15-20%), the increased surface instability across the southern border of the forecast area and increased moisture in the mid levels would certainly support the development of a few isolated storms entering into southern Grant county Thursday. Lawhorn/82 .LONG TERM...Friday through Tuesday...Models have come into better agreement in the long term period with fewer significant differences. The main focus of the long term will be a strong ridge over the area with a heat wave Friday and Saturday and the chances for afternoon and evening thunderstorms Friday through Sunday. The Extreme Forecast Index highlights temperatures Friday and Saturday with values of 0.85 to 0.90. Friday has the highest values mainly in Oregon and especially over the mountains. Saturday the entire area is highlighted with a Shift Of Tails over the Washington Columbia Basin and eastern mountains of Oregon suggesting a more extreme event is possible. Similar values, if not a little higher, are present in the overnight lows Friday night through Sunday night. Sunday drops down to 0.78 with the highest values in the Columbia Basin. Values indicate warm but not unusual temperatures Monday through Tuesday. Instability is also highlighted Friday through Sunday. Friday highlights the Oregon Cascades and the Ochoco-John Day Highlands and Southern Blue Mountains with a value of 0.83. Saturday has the strongest highlight with a value of 0.96 and the highest values are over the Cascades and the eastern mountains. This day will have the best chance for thunderstorms. The value drops to 0.82 on Monday mainly over the eastern mountains. For Friday, clusters show excellent agreement in having a strong ridge centered over the Rockies with a southwest flow over our area. Temperatures will rise about 5 degrees from Thursday with highs in the upper 80s to mid 90s and in the mid 70s to mid 80s in the mountains. This will be about 15 degrees above normal for early June. Overnight temperatures in the Columbia Basin will be 60 to 65 which will provide little heat relief and this will create moderate heat risk levels Friday and Saturday. The Columbia Basin will have a 70-90 percent chance of 90 degree temperatures and the Blue Mountain Foothills and central Oregon will have a 35-50 percent chance of 90 degree temperatures. Only the Tri-Cities area reaches a 10 percent chance of 100 degree temperatures. With moisture in a southwest flow and increasing instability, have a slight chance of thunderstorms in the late afternoon in the Ochoco Mountains and John Day Basin. Saturday, model clusters show some minor differences in the strength of the ridge and the axis location, but it remains similar to Friday. Temperatures warm a couple of degrees in the Columbia Basin and the eastern portions of the area though in central Oregon temperatures cool a couple of degrees, presumably due to increasing clouds and chances for showers and thunderstorms in the afternoon. High temperatures will be in the lower to mid 90s in the Columbia basin and in the 80s elsewhere. Chances of reaching 90 degrees are above 90 percent in the Columbia Basin and Yakima Valley and around 60-70 percent in the Kittitas Valley, Blue Mountain Foothills and Columbia Gorge. Chances are no more than 25 percent elsewhere. Hermiston and the Tri-Cities have a 20-25 percent chance of reaching 100. Thunderstorms are expected to develop in the afternoon with a slight chance to chance mainly over the eastern mountains. On Sunday models bring some form of trough to the west coast and shift the ridge eastward a couple of hundred miles. This will give us a marine push through the Cascade gaps in the afternoon with winds increasing to 10 to 20 mph. This will cool temperatures 5 to 8 degrees and limit a slight chance of showers and thunderstorms mainly to the higher terrain of the eastern mountains. Highs will drop to the mid 80s to lower 90s with mid 70s to lower 80s in the mountains. On Monday, model clusters mostly want to have a ridge over the area though 10 percent of model members keep a weak trough over the area. By Tuesday, all members have a broad trough centered over our area. Have kept temperatures a degree or two warmer than Sunday with highs in the mid 80s to lower 90s with mid 70s to mid 80s in the mountains. Do not foresee any precipitation Monday and Tuesday. Perry/83 && .AVIATION...Previous Discussion...18Z TAFs...A weak disturbance is bringing increased cloudiness with BKN-OVC CIGs at 050-080. Showers will remain over the mountains through this afternoon but have only included VCSH at KDLS through 21Z. Other TAF sites are expected to remain dry through the next 24 hours. Skies will be gradually clearing through the day and all TAF sites become SKC from 06Z-11Z. Winds are increasing and will be strong this afternoon but not to the degree it was yesterday. All TAF sites will have westerly to southwesterly winds at 15-25 kts with gusts to 35 kts from 20Z-06Z. winds will drop to below 12 kts after that. Perry/83 && .PRELIMINARY POINT TEMPS/POPS... PDT 50 77 49 83 / 10 0 0 0 ALW 51 79 51 86 / 10 0 0 0 PSC 53 81 52 88 / 0 0 0 0 YKM 44 78 47 86 / 10 0 0 0 HRI 51 81 50 88 / 0 0 0 0 ELN 43 74 47 83 / 0 0 0 0 RDM 47 80 47 84 / 0 0 0 0 LGD 49 77 49 83 / 10 0 0 0 GCD 48 83 51 89 / 0 0 0 0 DLS 51 81 52 87 / 10 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...Wind Advisory until 8 PM PDT this evening for WAZ521. && $$ SHORT TERM...82 LONG TERM....83 AVIATION...83