Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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983 FXUS66 KPDT 242330 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 430 PM PDT Tue Sep 24 2024 Updated Aviation Discussion .AVIATION...00Z TAFs...VFR conditions expected over the next 24 hours. Cloud decks will drop to around 10k feet starting tomorrow afternoon with the cold front. A chance of showers should be creeping up on most sites by late in the period, but for now have left rain out and will look for more exact timing on the 06Z update. Winds 10 knots or less expected overnight, becoming gusty tomorrow all sites as the cold front moves across the region. Goatley/87 && .PREV DISCUSSION... /issued 336 PM PDT Tue Sep 24 2024/ SHORT TERM...Tonight through Thursday night...The strong ridge of high pressure overhead will persist through tonight, shifting east through the day Wednesday as a shortwave trough and attendant strong cold front sweep across the Pacific Northwest. Southerly winds across the Blue Mountains and adjacent foothills overnight coupled with the lingering warm air mass (850-mb temperatures of 20-25 C) should facilitate some warm overnight low temperatures relative to climatology (ECMWF EFI of 0.6-0.95). Wednesday afternoon and evening, a strong Pacific cold front will sweep across the Pacific Northwest. NWP guidance suggests the closed low offshore of central California will eject north- northeastward and merge with the approaching shortwave trough as it tracks into the region. Southwesterly flow aloft will advect steep (7-8.5 C/km) mid-level (700-500 mb) lapse rates across eastern Oregon Wednesday, aiding in some modest instability of a couple hundred J/kg of MUCAPE. Synoptic forcing and orographic lift may facilitate isolated thunderstorms across portions of the Blue Mountains and WA Cascade crest (10-20% chance) Wednesday afternoon and evening, though confidence is higher in showers (15-60% chance). Winds will be the primary concern for Wednesday; 700-mb and 850-mb jets of 40-60 kts and 30-40 kts, respectively, signal enough momentum aloft for widespread breezy to windy westerly winds with frontal passage. Have issued wind advisories, in effect 11 am to 11 pm, for much of the Columbia Plateau. Recently plowed fields may also pose a concern for patchy to areas of blowing dust across the lower Columbia Basin, and blowing dust advisories have been issued. Drier conditions return Thursday in the wake of the cold frontal passage. Plunkett/86 LONG TERM...Friday through Tuesday... Bottom Line Up Front 1. High mountains showers Friday 2. Quite weather through the period Models are in decent agreement with an upper level shortwave bringing very light showers to the WA Cascades while the remainder of the region stays under dry zonal flow. 80% of the raw ensembles show Snoqualmie Pass will see upwards of 0.02 inches of rain and probabilities steadily decrease as you move southeast into the eastern slopes. Raw ensembles decrease to 20% as you reach Ellensburg then dissipate completely east of Vantage. Models show the majority of the rainfall to cease near 11 AM and mostly zonal flow will take over Friday afternoon and continue through Friday night. Models show a disturbance off the coast of the PacNW which will shift the flow aloft to a more southwestern component. However, models keep the region dry through Monday. Clusters show the majority of the ensembles to be favoring the slight southwest flow through day 6 before clusters show variances between the ensembles with whether an upper level ridge or an upper level trough will move overhead. Regardless, models show the forecast area to be under dry conditions Friday through Tuesday with slight chances (>15%) of rain returning to the high crests of the WA Cascades. With that said, fall like temperatures will prevail through the period with the EFI favoring at or near normal seasonal conditions. 80-100% of the raw ensembles show Friday and Saturday to be the warmest days with temperatures across the majority of the lower elevations and central OR to be in the mid to high 70s with isolated spots in the Ochoco-John Day Highlands and John Day Basin seeing mid 80s. The remainder of the period, 70-80% of the raw ensembles have the lower elevations and central OR in the low to mid-70s with higher elevations in the mid 60s. Bennese/90 && .PRELIMINARY POINT TEMPS/POPS... PDT 58 83 47 73 / 0 20 40 0 ALW 64 87 50 76 / 0 20 50 0 PSC 62 87 51 76 / 0 20 30 0 YKM 55 81 40 73 / 0 30 20 0 HRI 60 84 49 76 / 0 20 30 0 ELN 57 79 43 72 / 0 50 20 0 RDM 54 81 40 78 / 0 10 20 0 LGD 57 87 47 77 / 0 20 50 0 GCD 54 86 47 80 / 0 20 20 0 DLS 60 79 50 77 / 0 40 20 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Wind Advisory from 11 AM to 11 PM PDT Wednesday for ORZ041-507- 508-510. Blowing Dust Advisory from 11 AM to 11 PM PDT Wednesday for ORZ044. WA...Wind Advisory from 11 AM to 11 PM PDT Wednesday for WAZ024-026- 027-029-521. Blowing Dust Advisory from 11 AM to 11 PM PDT Wednesday for WAZ028. && $$ SHORT TERM...86 LONG TERM....90 AVIATION...87