Scientific Forecaster Discussion
000 FXUS66 KPDT 222152 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 250 PM PDT Sun Apr 22 2018 .SHORT TERM...Tonight through Wednesday...A weak trough of low pressure is crossing interior WA/OR this afternoon. Little/no deep layer moisture is associated with the trough, with mostly sunny skies area wide. The trough will exit to the east tonight, and with any pooling of moisture well to the east, expect mainly clear skies tonight. With light winds, this will result in good radiational cooling. There is some disagreement in model solutions, with the blend of all models in the mid 30s for the lower elevations, while the MET/MAV/ECS numeric guidance is clustered around freezing. Given last nights readings leaning toward the cooler guidance, will blend the numeric guidance, with lower 30s for most lower elevation locations. An hour or two of freezing temperatures will be possible but with scattered coverage of freezing temperatures, will not issue a freeze warning. Ridging will build across the area Monday, hovering over the region and amplifying Tuesday and Wednesday. Clear skies will prevail, with a significant warmup. Expect slightly above normal highs Monday, rising through the 70s Tuesday, with the warmest temperatures this spring thus far Wednesday with lower 80s for the lowest elevations. .LONG TERM...Wednesday night through Sunday night...Mid-upper level ridge of high pressure will still be over the forecast area Wednesday night. Thursday the ridge axis moves into Idaho thus allowing flow aloft east of the Cascades to back to the south, which opens the door for a large mid-upper level low pressure system near 132W roughly west of northern California to ease its eastern flank southerly flow aloft into central Oregon for, but deep layer moisture will be a tad to dry to support moist convection in central Oregon through Thursday afternoon. Compromise between the 12Z GFS and ECMWF runs for Thursday going forward. The ECMWF has shown the best day-to-day run consistency so forecast is based on that model. Thursday night the low introduces a moisture plume into the region for increasing chances of showers through Sunday night. Slight chance of thunderstorms Friday and Friday night in eastern Oregon. Polan && .AVIATION...18Z TAFs...VFR conditions for the next 24 hours. Variable high clouds 30K feet AGL decreasing this afternoon. Light upslope winds during daylight hours transitioning to downslope drainage winds this evening. Polan && .PRELIMINARY POINT TEMPS/POPS... PDT 35 67 37 75 / 0 0 0 0 ALW 37 70 40 77 / 0 0 0 0 PSC 32 72 35 77 / 0 0 0 0 YKM 33 71 36 75 / 0 0 0 0 HRI 32 70 33 77 / 0 0 0 0 ELN 32 67 37 71 / 0 0 0 0 RDM 23 68 28 76 / 0 0 0 0 LGD 31 64 35 70 / 0 0 0 0 GCD 34 66 38 72 / 0 0 0 0 DLS 36 73 37 78 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None.