Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
909 FXUS66 KPDT 171707 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 1007 AM PDT Tue Jun 17 2025 .UPDATED AVIATION DISCUSSION. .AVIATION...18Z TAFs...Conditions are forecasted to remain in VFR for the entire period for every site. The only concern for this period, and what we will have to look out for, is the locally breezy to windy conditions that will impact some areas over the next 24 hours. A weak weather system will continue its influence on the pattern, bringing gusts up to 25 knots at PDT/DLS for the majority of the period. RDM/BDN will see their winds increase up to 20 knots by 00z today. Otherwise, CIGs and VIS remain elevated to VFR and no precip is anticipated at this time. && PREV DISCUSSION... /issued 119 PM PDT Mon Jun 16 2025/ SHORT TERM...Tonight through Wednesday...current satellite data this afternoon shows areas of cumulonimbus with towering cumulus developing across the higher terrain of the Strawberrys, southern Blues, and Wallowa mountains, while cirrus decks move across the rest of the forecast area. Regional radars have also shown a few convective showers develop in the developing cumulonimbus fields, with lightning detection networks picking up a few in cloud strikes and a cloud to ground lightning strike as well. Today, a shortwave trough moving across the region will continue to provide a chance (20-30%) of showers along the mountainous terrain of the southeastern and easter border of the CWA, with a slight chance (10-20%) of isolated thunderstorms mixed in as well. The bigger concern today will be the breezy to windy conditions developing through the Kittitas valley and the eastern Gorge coupled with the dry conditions that have settled into the region. Currently, confidence is high (75-90%) that winds will be 20-30mph with gusts 30-40mph, with winds generally 15-20mph and gusts up to 35mph in the Columbia Basin. While winds will be critical through the Cascade gaps zones, confidence is high (80%) that relative humidities in the Kittitas valley will reach critical levels and overlap with critical winds, so a Red Flag Warning is in effect through 9PM this evening. Shower activity will diminish this evening as the shortwave trough axis exits into the northern Rockies, while winds will be slow to diminish this evening and overnight. Tomorrow, a dry zonal flow aloft will develop, resulting in dry conditions area wide. However, surface pressure gradients across the Cascades will still remain between 5-7mb, resulting in breezy conditions (winds 15-25mph with gusts 30-35mph) through the Cascade gaps Tuesday afternoon. Wednesday, another weak shortwave with a surface cold front will impact the PacNW with shower activity confined to the central WA Cascade crest. Surface pressure gradients will tighten to around 6-8mb across the Cascades again, resulting in breezy to windy conditions (20-30mph sustained with gusts up to 40mph) developing through the Cascade gaps. A marine push and slightly cooler air accompanying this system will result in relative humidities staying above critical thresholds, though strong winds will still lead to increased fire weather concerns through the evening. Lawhorn/82 LONG TERM...Thursday through Monday...Sensible weather concerns through the extended forecast will revolve around an upper low passage over the weekend that will produce widespread rain shower chances, breezy to locally windy conditions, and bring below normal temperatures as well. Thursday, the upper low in the Gulf of Alaska will begin to drop south while flow aloft over the PacNW becomes more southwest. The flow will be fairly dry, and precipitation/thunderstorm chances over the eastern mountains and central OR will be very low (<10%) throughout the day. Breezy conditions will develop through the Cascade gaps with winds mainly 15-25mph and gusts up to 35mph. While Thursday will be the last of the dry days for the week, confidence is mod-high(60-80%) that winds will remain below critical thresholds for fire weather concerns. Friday through Sunday, ensemble guidance is in great agreement that the closed upper low will swing into the PacNW with main circulation exiting into Alberta and Saskatchewan by Sunday afternoon. This will result in some form of troughing developing over the west coast through early next week. Confidence is mod- high (70-80%) that widespread showers will develop across the area Friday and Saturday. A much cooler airmass will also accompany the upper low passage, which will result in below normal temperatures (60s to mid 70s lower elevations...mid 40s to lower 60s mountains and intermountain mountain valleys) through the weekend. Sunday into Monday, ensemble cluster solutions do differ on the extent and timing of shower activity owing to the differences in the troughing solutions. That said, confidence is still moderate (50-70%) in shower activity continuing across the mountains both days. Otherwise, confidence is mod-high (60-80%) that breezy to windy conditions will develop Friday and Saturday through the Cascade gaps and into the lower elevations, with light winds developing Sunday into Monday. Lawhorn/82 && .PRELIMINARY POINT TEMPS/POPS... PDT 86 55 84 49 / 0 0 0 0 ALW 85 59 84 54 / 0 0 0 0 PSC 88 55 87 50 / 0 0 0 0 YKM 87 54 84 49 / 0 0 0 0 HRI 88 57 86 51 / 0 0 0 0 ELN 83 53 78 48 / 0 0 0 0 RDM 83 43 81 39 / 0 0 0 0 LGD 83 50 83 48 / 0 0 0 0 GCD 84 49 86 47 / 0 0 0 0 DLS 84 57 78 52 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...82 LONG TERM....82 AVIATION...95