Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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963 FXUS66 KPDT 102313 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 413 PM PDT Mon Jun 10 2024 Updated aviation discussion .SHORT TERM...Tonight through Wednesday...Very little in the way of activity across the forecast area this afternoon, as satellite imagery only shows a few cumulus clusters developing across far northeast OR and southeast WA. That said, breezy winds have developed through the Cascade gaps thanks to a temperature differential between the west and east sides of OR/WA. Tonight, the transient ridge currently over the PacNW will be pushed east by an approaching upper trough and attendant surface cold front. The coupled system will remain fairly dry as it transits the region tomorrow, with best chances of precipitation along the coastal ranges and the WA Cascades, where there is only a 35-45% chance of 0.01 inches of precip along the central WA Cascade crest. Though dry, the cold front will be strong enough to tighten pressure gradients between Portland and Spokane to around 11mb tomorrow afternoon. This will translate to breezy west winds generally 20-30mph through the Cascade gaps, as well as the Columbia Basin and adjacent valleys/foothills. Winds will be stronger in the Kittitas valley tomorrow where a wind advisory is in effect, with the probability of 24hr max sustained winds greater than 30mph and max gusts greater than 45mph are between 75-95%. While the NBM does show similar probabilities of these wind speeds/gusts in the Columbia Basin, HREF members keep winds below criteria, and without the support of an 850mb jet confidence in windy conditions is only 50-60%. The shortwave and cold front will exit the forecast area tomorrow evening, allowing winds to diminish through the late evening and overnight hours. Wednesday, a zonal flow aloft will be the dominant pattern throughout the day, resulting in locally breezy to breezy winds through the Cascade gaps and overall dry conditions across the forecast area. Lawhorn/82 .LONG TERM...Thursday through Monday...A cooler, wetter pattern is in store for the forecast area as ensemble guidance keys in on a deep upper-level low that looks to envelop the region by sometime next weekend. As a result, expect below-average temperatures, persistent PoPs - especially across our mountain zones - and periods of breezy winds across much of the CWA. This upper-level low, initially centered off BC, will impact the area in two distinct waves: the first via a band of amplified SW flow aloft through the leading edge of the system, which is expected to begin around the midweek and last through the beginning of next weekend, and the second via the arrival of the low`s center itself. Ensemble guidance does disagree on the exact track of the low, as some members have the system skirting us more to the north, while others bring the center of the low more overhead of the PacNW. A more northward track of the low would invite a wetter forecast, as moisture advection would be more persistent into the area, while the low`s center falling overhead would bring in colder air, but not quite as wet of a forecast. Still, confidence is high (60-70%) that temps late this week and over the weekend will fall below average starting Saturday, to around 5 to 10 degrees below seasonal values, possibly more should the low track a bit more southward. Confidence is also high (60%) that our mountains will see a wet forecast for most of the period. QPF isn`t particularly impressive this far out, but the pattern is conducive for showers for much of the period. Would expect some higher PoPs across the lower elevations given the pattern depicted across deterministic guidance as well, but I suspect that model climatology is playing a role here. Models do tend to be a bit gun-shy this time of year with regards to depicting precip outside of the mountains during the long term. Expect winds to rear their ugly heads once again due to this low`s influence as well. EFI doesn`t quite tap into extreme wind values for the forecast area as of now, but NBM probabilistic guidance does depict high probabilities (50-80%) for wind gusts to exceed 30 mph across much of the forecast area Friday through the weekend. Evans/74 && .AVIATION...00z TAFs...VFR conditions expected for the period. Expect clear skies then some SCT high clouds on Tuesday. winds will be 5-15kts through the evening then light overnight. Winds increase on Tuesday morning becoming west 10-20kts with gusts 30-35kts. && .PRELIMINARY POINT TEMPS/POPS... PDT 55 83 47 77 / 0 0 0 0 ALW 59 87 50 79 / 0 0 0 0 PSC 60 90 52 82 / 0 0 0 0 YKM 56 83 46 80 / 0 0 0 0 HRI 58 87 50 82 / 0 0 0 0 ELN 55 75 46 74 / 0 0 0 0 RDM 51 81 42 76 / 0 0 0 0 LGD 52 82 44 74 / 0 0 0 0 GCD 53 85 45 79 / 0 0 0 0 DLS 58 79 50 79 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...Wind Advisory from 9 AM to 11 PM PDT Tuesday for WAZ026. && $$ SHORT TERM...82 LONG TERM....74 AVIATION...74