Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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178 FXUS66 KPDT 190519 AAC AFDPDT Area Forecast Discussion...UPDATED National Weather Service Pendleton OR 1019 PM PDT Wed Sep 18 2024 Updated Aviation Discussion .AVIATION...06Z TAFs...VFR conditions expected over the next 24 hours with skies clear. Winds generally 10-12 knots or less, though sites DLS/PDT could see gusts around 20-25 knots. Goatley/87 && PREV DISCUSSION... /issued 252 PM PDT Wed Sep 18 2024/ SHORT TERM...Today through Friday night... Key Messages: 1. Breezy afternoon conditions each day, peaking Thursday evening. 2. Warming through Thursday, cooler through the end of the week. Current radar and visible satellite imagery showing dry conditions as mostly clear to partly cloudy skies extend across the area as clouds mainly impact areas of elevation over the Blue Mountains. These conditions are in response to our proximity to two upper level systems, one continuing to depart through southeastern Montana and the other dropping south along the coast. These exiting systems will open the door to upper level ridging infiltrating into the area from the west this evening into Thursday. As a result, clear to mostly clear skies and dry conditions will persist through Friday. A pressure gradient has already developed along the Cascades as high pressure pushes onshore, which has allowed for breezy winds to occur across the Gorge, Kittitas Valley, and portions of the Basin today. Gusts of 20-25 mph have been recorded at the Dalles and Ellensburg this afternoon, which will linger until between 7PM and 8PM before slowly subsiding tonight. These elevated winds are expected to return each afternoon, peaking late Thursday afternoon and evening as an upper level shortwave rides along the Canadian border and further tightens pressure gradients. Gusts of 30-35 mph will be possible Thursday afternoon/evening and 25-30 mph Friday afternoon/evening over the aforementioned areas. Confidence in these wind values is moderate to high (60-80%) as the NBM advertises a 90-95% chance of 30 mph gusts across the Kittitas Valley and a 55-75% chance through the Gorge, Simcoe Highlands, and portions of the Basin west of Hermiston both days. Confidence is high (90-95%) that expected winds both days will stay below advisory criteria (Sustained winds of 30 mph and gusts of 45 mph) through Friday as suggested by only a 5-15% chance of 45 mph gusts or greater via the NBM. The upper level flow is out of the north today, and will turn more out of the west on Thursday to allow high temperatures to increase 2 to 5 degrees and break into the low 80s across lower elevations of the Basin. Confidence in high temperatures of 80 degrees or greater for Yakima, Hermiston, and the Tri-Cities is moderate to high (65-80%) per the NBM. Flow aloft turns more out of the northwest on Friday to bring a cooler airmass across the area as highs drop 4 to 8 degrees from Thursday. Normal high temperatures for this time of year is around 77 degrees, so these values will be briefly above normal on Thursday before returning to below normal on Friday. Mostly clear skies overnight will also provide cool morning temperatures as lows will bottom out in the upper 30s to low 40s over Central Oregon and the Grand Ronde Valley both Thursday and Friday night. Confidence is high (70-90%) in this occurring as the NBM showcases a 65-85% chance of low temperatures reaching below 40 degrees for Redmond and La Grande Friday night. 75 LONG TERM...Saturday through Wednesday...Generally dry northwesterly flow will start out the extended period on Saturday, though some weak shortwave energy could potentially touch off a shower over the Washington Cascades. Probabilities at this time are too low to mention in the forecast. The northwest flow will strengthen Sunday into Monday as a ridge builds over the Pacific. However, by Sunday in to early Monday, some moisture will move over the ridge and will bring some rain potential to the Washington Cascades beginning Sunday and to the eastern mountains later Sunday into Monday. These showers should be relatively light. The higher elevations of the Washington Cascades could get up to one quarter of an inch with much less elsewhere. Most of the areas that do receive precipitation will get a few hundredths at best. The ridge over the pacific will then move inland for Monday and Tuesday and bring dry weather everywhere. Another trough will approach the region Tuesday night and bring a return to a zonal flow on Wednesday, with shower chances returning to the mountains. There will be diurnal breeziness on Sunday and Tuesday and Wednesday, but winds should generally be less than 25 mph. The NBM probabilities of wind gusts >=39 mph on Sunday are generally less than 30 percent, though there are a few isolated spots tin the 30 to 40 percent range across the Columbia Basin and Simcoe Highlands. On Wednesday, probabilities of wind gusts >=39 mph rise to the 40 to 50 percent range across the Columbia Basin, Simcoe Highlands and Kittitas Valley, as the westerly flow moves in. However, this is day 7, so we will see how this plays out across the area. Overall, the model guidance is in very good agreement through the period. High temperatures will be generally near normal, rising to 5 to 10 degrees above normal by Tuesday (and into the lower 80s in some areas) under the ridge. && .PRELIMINARY POINT TEMPS/POPS... PDT 48 77 47 69 / 0 0 0 0 ALW 52 79 51 72 / 0 0 0 0 PSC 55 81 53 75 / 0 0 0 0 YKM 49 80 47 75 / 0 0 0 0 HRI 53 80 52 75 / 0 0 0 0 ELN 49 76 49 72 / 0 0 0 0 RDM 43 77 41 72 / 0 0 0 0 LGD 46 78 45 69 / 0 0 0 0 GCD 45 77 43 72 / 0 0 0 0 DLS 53 80 53 72 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...75 LONG TERM....77 AVIATION...87