On March 18, 1998, at 0441 hours mountain standard time, a Cessna 421B, N70PD, ran off runway 24 during the initial takeoff roll and collapsed the nose gear at Show Low, Arizona. The aircraft sustained substantial damage. The pilot, paramedic, and flight nurse were not injured. The aircraft, operated by American Corporate Aviation, d.b.a. Medical Express International Inc., was on a 14 CFR Part 91 repositioning flight to pick up an injured person at Zuni Pueblo Airport when the accident occurred. The aircraft was on an IFR flight plan and instrument meteorological conditions prevailed at the time of the accident. The pilot stated that he filed an IFR flight plan and received his clearance from his cellular telephone while he was holding his position on the runway. He said he released the parking brake and began what seemed to be a normal takeoff roll on runway 24. He stated that it was snowing with approximately 2 miles visibility and the runway was wet with some accumulation of snow and slush. About 200 feet on the takeoff roll, with the airspeed indicator showing 40-50 knots, the airplane began to veer to the left. The pilot said he responded initially with differential power and full right rudder but that this had little corrective effect. The right wheel departed the pavement about 500 to 750 feet, and the takeoff was aborted by retarding the throttles and applying the brakes. The airplane came to rest in the mud to the left of the runway in a nose down attitude, with the nose gear collapsed. According to the Federal Aviation Administration (FAA) inspector who traveled to the scene, witnesses stated that it was snowing heavily at the time of the accident. The inspector estimated that the pilot taxied the airplane about 1/2 mile to reach the end of the runway. He said there was a displaced threshold at the end of runway 24 and the runway lights were hard to see because of the snow. He also noted that the pilot could not see the runway lines and only the taxiway lines and runway edge lines were visible on the snow-covered runway. The FAA representative stated the starting point and where the airplane finally ended up was a straight line on the runway edge side stripe, which was approximately 20 feet to the left of the runway centerline marking. The pilot told the inspector that the snow was accumulating rapidly on the windshield, but that he thought it wouldn't be a factor once he began his takeoff roll. He stated that the aircraft yawed to the left and that it felt like the left brake was "dragging" prior to the airplane going off the runway.