One of the jet check airmen just told me that they were authorized to 1000 RVR (Cat II minimums).
Seattle and Portland have been EXTREMELY foggy for the last four or five days. I've done three Cat III's into Seattle in the last three days, the last two to 800 RVR and 600 RVR, respectively. The approach on Monday was probably the lowest one I've ever done at Seattle. The ILS wasn't too bad, but taxiing was very stressful, particularly with the construction at Seattle. My FO did a great job with helping me to maintain orientation as we wound around construction barricades, dodged catering trucks, and attempting to find our parking spot. It was so foggy that I had a hard time seeing our marshaller at 400 feet, lighted wands and all.
At the present time, Seattle is limited to 600 RVR for all operations, due to the construction. This applies to all operators, not just Horizon.