Marginal destination forecast, a wet alternate, and a fuel plan with almost no slack

An alternate is required unless the destination forecast, for the period from 1 hour before to 1 hour after your ETA, shows at least a 2,000-ft ceiling and 3 SM visibility. Eugene's window is 2200Z to 0000Z. The main forecast body already shows OVC008, an 800-ft ceiling, so the alternate requirement is triggered before the TEMPO is even considered. The TEMPO 2200/2204 falls inside the window and drops visibility to 2 SM with OVC005; both values are below the trigger, so treat it as the likely condition rather than a remote possibility. Portland then has to satisfy the alternate minimums for the approach you would fly: 600 ft and 2 SM for a precision approach, 800 ft and 2 SM for a non-precision approach. For the alternate ETA window, Portland's forecast is P6SM SCT030 BKN060, far above either standard, and the FM0200 group remains legal too. The trap is assuming Eugene will improve enough to skip the alternate; both the TEMPO and the FM0000 OVC006 say the ceiling stays low, so plan to use the alternate.

Required fuel is destination plus alternate plus 45 minutes at normal cruise. Destination: 200 NM at 115 KTAS is about 1.75 hr, or 17.5 gal. Alternate: 0.5 hr, or 5 gal. Reserve: 45 min, or 7.5 gal. Total 30 gal, plus 1.5 gal for taxi, equals 31.5 gal against 34 gal aboard. That is legal with roughly 2.5 gal, about 15 minutes, in reserve above the requirement. The margin exists only on paper: it assumes no missed approach, no holding, and the forecast winds. With Eugene at an 800-ft ceiling and TEMPO 2 SM, a missed approach is a realistic outcome, and a miss plus the alternate costs another 10 to 12 minutes. Any holding at either airport erases the margin entirely. With 15 minutes of slack, the correct decision is to add fuel (the airplane holds 48 gal usable, so there is room) or accept a plan that does not depend on the alternate. If you launch with 34 gal, set a hard decision point: a missed approach or any holding means diverting immediately, not after one more attempt.

At 9,000 ft the OAT will be near -2 C with the freezing level at 7,500 ft, and the layer is solid up to 12,000 ft, so the flight would spend well over an hour in visible moisture below freezing in an airplane not approved for known icing. That is not a plan you can defend. The usable alternative is 6,000 ft: it is the MEA, it puts you about 1,500 ft below the freezing level in above-freezing air, and it is above the minimum vectoring altitude. It is also a correct even-thousand altitude for the southbound direction of flight. Ask for 6,000 ft when you file or when you pick up the clearance, and state plainly that you are unable to accept 9,000 because of icing. Expect a slower true airspeed and more fuel burn down low, so recheck the numbers from the fuel question. Monitor the OAT in the climb and be ready to request a further descent if the temperature at 6,000 ft approaches freezing or if any ice begins to accumulate, because ATC has no way to know what your airframe is picking up.