Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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680 FXUS66 KPDT 112324 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 424 PM PDT Tue Jun 11 2024 .Updated for Aviation... .AVIATION... 00Z TAFS...High Confidence (95-100%) in VFR conditions through the period. Gusty winds this evening will subside in most locations this evening and everywhere overnight, with winds becoming 10 kts or less and remaining there. The only exception is DLS which will have gusty winds 20 to 25 kts again Wednesday afternoon. && .PREV DISCUSSION... /issued 258 PM PDT Tue Jun 11 2024/ SHORT TERM...Tonight through Thursday Night... Key Messages: 1. Breezy to windy conditions through this evening with wind advisories issued for the Kittitas Valley, Eastern Columbia Gorge and Simcoe Highlands. 2. Cooler Wednesday but warming back up Thursday. A weak shortwave is passing to our north through central British Columbia this afternoon and it has a cold front that will cross our area a few hours from now. Radar is not showing any shower activity and satellite shows clouds mainly west of the Cascades with mostly clear skies over our area. The main concern today is the winds, which will be peaking later this afternoon and then decreasing this evening after sundown. The GFS, NAM, SREF and GEFS all have pressure differences between Portland and Spokane in excess of 10 MB with the RAP is between 9-10 MB. These values point to windy conditions in the Columbia Basin and adjacent valleys. Observations have been mainly in the 20 to 30 mph with gusts to 35-40 mph so far but winds are increasing. Ellensburg had northwest winds of 31 mph gusting to 46 mph in the latest observations. NBM probabilities show a greater than 90 percent chance of wind gusts of 40 mph in Kittitas Valley. Simcoe Highlands, Columbia Gorge and and a 50-90 percent chance in the Blue Mountain Foothills later this afternoon. Chances for a wind gust of 49 mph are 70 percent chance in the Kittitas Valley and 50- 60 percent in the Simcoe Highlands and Columbia Gorge but drop off to less than 15-30 percent elsewhere. Current wind advisories for the Kittitas Valley, Simcoe Highlands and the Eastern Columbia River Gorge look good and will remain in effect through 11 PM this evening. Winds look to remain just below wind advisory levels in the Columbia Basin, Blue Mountain Foothills and Yakima Valley. Relative humidities are as low as 20-25 percent as well and a few weeks from now, would probably need to consider a Red Flag Warning for fire danger but believe the vegetation is still a bit too green for large fires. As winds die down this evening after the cold front passage, colder air will move over the area and along with clear skies, temperatures will drop off as much as 8 to 12 degrees from last night with lows in the 40s in the lower elevations and in the mid 30s to lower 40s in the mountains. Tomorrow, with the shortwave moving into the Rockies and the next trough still up in the Gulf of Alaska, a zonal westerly flow will be over the area and sunny and dry weather is expected. Winds will be fairly light with only the Kittitas valley and Columbia River Gorge reaching 10 to 15 mph in the afternoon. Lingering cooler air will drop temperatures 5 to 8 degrees from today and highs will be in the mid 70s to lower 80s in the lower elevations and in the mid 60s to mid 70s in the mountains. Lows Wednesday night will be a few degrees warmer than tonight but still a few degrees below normal in most locations. On Thursday, a strong upper low and trough will begin moving south out of the Gulf of Alaska to the central british Columbia coast. This will send a warmer southerly flow over our area. There will continue to be no chance of precipitation through Thursday night but there will be increasing cloudiness along the Cascades and in the northern portion of the area in the afternoon and Thursday night. Winds will continue to be light through Thursday evening but will become breezy overnight in the Columbia Basin and adjacent wind prone valleys. Highs Thursday will rebound back to the lower to mid 80s with 70s and lower 80s in the mountains. Lows Thursday night will warm to the mid 40s to mid 50s. Perry/83 LONG TERM...Friday to Tuesday...The main sensible weather highlights include: - Breezy to locally windy conditions across our windy/climo-prone areas Friday and Saturday, - Cooler, below normal temperatures with the coldest conditions this weekend, particularly Sunday, and - Unsettled weather this weekend onward with generally periodic chances, highest along the crest of the Cascades and eastern mountains. The long term initially will be characterized by a deep, anomalous upper-level closed low offshore British Columbia with southwest flow aloft with the expectation of a weak front moving across Thursday night. Ensemble guidance is in very good agreement with the synoptic pattern as cyclonic flow dominates through Saturday with the upper trough forecast to evolve to the WA/BC region. A modest synoptically imposed surface pressure gradient will develop late Friday and persist Saturday with the stronger winds prevailing Saturday. Limited support aloft in the lower troposphere until more so Saturday. 24-hr peak daily gusts chances for exceeding 40 kts around 60-95% over the eastern Columbia Gorge into the Lower OR Basin, Simcoe Highlands, and the Kittitas Breezeway, highest across the later area. Slightly higher probs, by 10-15%, on Saturday across the same locations. That said, chances for exceeding 45 mph are around 25-50%, except for 60-90% across the Kittitas Valley. Meantime, the best chances (50-80%) for precip in the long term will arrive Saturday across the WA Cascades near the crest. As the upper trough evolves, an cooler air mass is anticipated to take hold this weekend. This in tandem with limited sky cover across some areas will favor radiational cooling when/if combined with light winds as well. Of which, lows will be around 3 to 10 degrees below normal area-wide Sunday morning across the lower elevations; lows will be into the 30s across parts of central OR. Confidence is low right now in central OR seeing lows below 32 with chances peaking around 25% across Redmond. Thereafter there are modest differences in the 500 mb pattern beginning Sunday that grow more by Monday/Tuesday next week with the latest guidance in fairer agreement compared to overnight. Specifically, the amplitude and character of the upper trough early next week. There is potential for embedded wave(s) to deepen this upper trough Monday over the Northern Intermountain West, or the other possible outcome is a pattern that becomes more progressive, less amplified with open waves/shortwave troughs passing across the PacNW. Confidence in more persistent upper-level troughing affecting the region around ~80% and 90% Monday and Tuesday, respectively. Currently there are low to moderate chances (15-50%) across the upper slopes of the eastern Cascades and the eastern mountains Sunday, highest odds in the former. Lower confidence on Monday and Tuesday with chances more broad and lower overall (15-40%). Lastly, there are concerns (~15-20%) for isolated thunderstorms Monday, however, confidence is low giving the spread in guidance and uncertainty this far out in time. AVIATION...Previous discussion...18Z TAFS...VFR conditions prevail during this TAF period. Most sites currently have FEW-SCT clouds except KRDM with clear skies. Cloud coverage will decrease throughout the day for KDLS/KPDT/KALW/KPSC. All sites will experience gusty westerly winds at 20-30kts with sustained winds at 15-25kts this late morning. These wind conditions should decrease overnight but afternoon for KDLS (>50% confidence). Feaster/97 && .PRELIMINARY POINT TEMPS/POPS... PDT 44 76 46 83 / 0 0 0 0 ALW 48 79 49 86 / 0 0 0 0 PSC 50 81 50 87 / 0 0 0 0 YKM 42 79 46 84 / 0 0 0 0 HRI 47 81 48 87 / 0 0 0 0 ELN 45 76 46 82 / 0 0 0 0 RDM 40 77 43 83 / 0 0 0 0 LGD 43 74 45 84 / 0 0 0 0 GCD 44 79 46 89 / 0 0 0 0 DLS 48 80 50 85 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Wind Advisory until 11 PM PDT this evening for ORZ041. WA...Wind Advisory until 11 PM PDT this evening for WAZ024-026-521. && $$ SHORT TERM...83 LONG TERM....80 AVIATION...77