Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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481 FXUS66 KPDT 242048 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 148 PM PDT Mon Jun 24 2024 .SHORT TERM...Tonight through Wednesday...A ridge of high pressure will continue building over the Pacific Northwest through Tuesday as an upper level trough in the Gulf of Alaska drops down towards the Pacific Northwest coast. This will boost Tuesdays high temperatures into the lower to mid 90s across the lower elevations and increase heatrisk to moderate. The upper level trough will begin moving inland Wednesday. Models are in good agreement that a shortwave rotating around the bottom of the trough will pass over the forecast area early Wednesday increasing instability leading to a low chance (15%) of showers and thunderstorms across most of the forecast area. Following the passage of the shortwave there will be increasing westerly winds of 15 to 25 mph through the day decreasing instability for some portions of the forecast area. Exception will be over the east slopes of the Washington Cascades and the eastern mountains. These areas will continue to see enough instability for convective showers and thunderstorm through the afternoon and into the evening. Some showers will persist along the Cascade crest Wednesday night as well as over the eastern mountains mainly east of Meacham as the overall upper level trough continues moving into the Pacific Northwest. The breezy conditions Wednesday will be in conjunction with minimum relative humidities dropping into the low to mid 20s. Combine this will the slight chance of thunderstorms early in the day across the Columbia Basin there is an elevated potential for increased rate of spread in fine fuel fires. .LONG TERM...Thursday through Monday... Bottom Line Up Front 1. Breezy conditions return Thursday. 2. Thunderstorms along the eastern mountains. 3. Below normal to near normal temperatures. Models are in decent agreement with an upper level low over the PacNW. The axis of energy is directly over the region with the center just to the north of the CWA. This will bring strong northwest flow across the Cascades. Looking at the surface guidance, gradients tighten to between 9 to 10 mb along the Cascades which will lead to an increase in winds, especially through the Gaps. The EFI is also picking up on the abnormally breezy conditions mainly along the Blue Mountains and into Wallowa County. However, winds along the northern Blues and Wallowa County be below 25 mph with no ensembles showing otherwise and only 10% probabilities for the Northern Blues. 65+% of the NBM ensembles show the two main areas that will see sustained winds of 25 mph and higher with gusts to 35 mph (70%) will be along the Simcoe Highlands and through the Kittitas Valley with 30-40% showing the Southern Blues to see the same with gusts at 70% for 35 mph as well. Once the upper level low moves to the east Thursday night, winds will return to near normal. With the upper low moving into the region bringing with it mid level moisture and some instability parameters. Looking at model derived soundings for Thursday afternoon, they show MUCAPE values between 350-500 J/kg, lifted index between -2 to -4, PWATs of 0.50-0.60 inches, lapse rates of 8.3 C/km and bulk shear nearing 40 kts. With all these parameters we cannot rule out some high based thunderstorms along the Northern Blues and Wallowa mountains Thursday afternoon and into the early evening. With that said, there are 15-30% probabilities of thunderstorms over the Blue and Wallowa mountains with the higher probabilities over the Wallowas. Lastly, the upper level low will bring with it some cooler temperatures to start the term with. However, EFI is showing temperatures to be at or just below normal. However, once the upper level low exits the CWA, a transient ridge will move back in overhead warming temperatures up again. Thursday is the coolest day of the period with over 60% of the raw ensembles having the temperatures for Pendleton in the mid 60s to low 70s, 60% shows the Gorge and central OR to be in the mid to upper 70s while the Basin and adjacent valleys will see temperatures in the upper 70s to low 80s. As the ridge slowly pushes over the area, temperatures will increase gradually each day until it maxes out on Sunday. However, confidence in the max temperatures of high 80s to low 90s so far out is low/moderate with on 30-40% of the ensembles in agreement for any portion of the CWA. Bennese/90 && .AVIATION...18Z TAFs...VFR conditions expected over the next 24 hours. Breezy winds possible for DLS with a few breezes around 10-12 knots possible at DLS, with winds 10 knots or less all other sites. Bennese/90 && .PRELIMINARY POINT TEMPS/POPS... PDT 51 92 58 84 / 0 0 0 20 ALW 54 95 59 88 / 0 0 0 20 PSC 57 96 63 90 / 0 0 0 20 YKM 53 92 60 87 / 0 0 0 20 HRI 54 96 62 88 / 0 0 0 20 ELN 51 90 57 82 / 0 0 0 20 RDM 47 91 57 81 / 0 0 10 20 LGD 51 90 58 85 / 0 0 0 20 GCD 52 95 56 89 / 0 0 10 20 DLS 55 94 61 80 / 0 0 0 20 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...91 LONG TERM....90 AVIATION...90