Scientific Forecaster Discussion
000 FXUS66 KPDT 241138 AAA AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 300 AM PDT Wed May 24 2017 UPDATED AVIATION .SHORT TERM...Today through Friday...Water vapor imagery shows a trough moving into the area with an upper low moving southeast along the Canadian Rockies towards northern Washington. A cold front is just about ready to move into Idaho. The front is very moisture starved and there has been no precipitation and few if any clouds. The main impact is increased winds though some areas are having a lull during the overnight hours. Ellensburg airport continues to have northwesterly winds at 25 to 35 mph with gusts to 45 mph so current wind advisory for Kittitas county looks good. The rest of the area will have west to northwest 15 to 30 mph winds with gusts to 35 mph through this afternoon. Do not think winds will reach advisory levels elsewhere, though it could be close for a few hours this afternoon in the Columbia Gorge, Columbia Basin and Blue Mountain Foothills. The other main impact will be temperatures as high temperatures today will be around 20 degrees cooler than yesterday. Highs will be in the upper 60s to mid 70s with upper 50s to mid 60s in the mountains. Tonight the upper low will move rapidly east into Manitoba but the trough will remain over our area with a northwest flow. Models show some moisture moving in this evening and a slight chance of showers developing in the Washington Cascades and eastern Oregon mountains in the late night and Thursday morning hours. A wave and instability under the trough will create a slight chance of showers and thunderstorms Thursday afternoon in the Cascades and from the Blue Mountain 06Z TAFs...VFR conditions will prevail during the next 24 hours. The main concern will be increasing winds this evening...especially at KDLS...KPSC...KALW...KPDT and KYKM. Winds in these locations will increase to at least 10 to 20 mph but more likely 15 to 25 kts...but likely staying below wind advisory criteria. Further south KRDM and KBDN will see an increase in wind as well...but not as much as the stations over the northern two thirds of the area. 88Foothills and Ochoco-John Day Highlands eastward. Do not expect any strong or severe thunderstorms. Rain amounts will be light and just a few hundredths of an inch in general. Showers will taper off in northeast Oregon during the evening. The trough will drift slightly eastward Thursday night and Friday and an offshore ridge will begin to build ashore. There will still be a moist northerly flow over the eastern half of the area and there will be a slight chance of showers and thunderstorms Friday afternoon over the northern Blue mountains and Wallowa county while the rest of the area is dry. Temperatures Thursday will warm a couple of degrees to the lower to mid 70s with mainly 60s in the mountains. Friday will be in the mid 70s to lower 80s with mid 60s to lower 70s in the mountains. Perry .LONG TERM...Friday night through Wednesday...GFS and EC models in good agreement. Both show upper level trof in ID with residual moisture and instability over the eastern mountains Friday evening. Upper level ridge builds over the area during the weekend with above normal temperatures and dry stable conditions. A southwest flow will return enough moisture for the slight chance of thunderstorms again Monday afternoon and also Tuesday and Wednesday afternoons. Upper level ridge combined with weak surface pressure gradient will keep winds light through the period. About the only impacts will be the much above normal temperatures resulting in high level snowmelt and increase runoff into some of the streams coming off the Cascades. 79 && .AVIATION...12Z TAFs...Wind will continue to be main factor in TAFs. Upper level trof combined with moderate to strong pressure gradient at the surface will produce west winds with g20-30kts diminishing after 03z. Mid and high clouds rotating around the back side of the trof will begin to affect eastern TAF sites after 00z. && .PRELIMINARY POINT TEMPS/POPS... PDT 67 44 67 46 / 0 10 20 20 ALW 70 49 70 51 / 10 10 20 20 PSC 74 47 75 49 / 0 10 10 10 YKM 73 47 76 49 / 0 10 10 10 HRI 72 46 72 47 / 0 10 10 10 ELN 66 44 73 47 / 0 10 10 20 RDM 69 34 70 38 / 0 0 0 10 LGD 64 41 63 41 / 10 10 20 20 GCD 68 39 67 42 / 0 10 20 20 DLS 69 48 78 51 / 10 0 10 10 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...Wind Advisory until 10 PM PDT this evening for WAZ026.