BE200 Captain reports encountering severe turbulence and windshear during night ILS approach to an uncontrolled airport. During the go-around a GPWS terrain warning was received along with two separate instances of stalling. Flight subsequently diverted to a nearby alternate.

Narrative

On the night of this flight there was a line of thunderstorms along our route. The movement suggested that we would be able to fly around the north of the storm and come in from the east side. The passengers were briefed on the weather and the assurance of a bumpy ride. They decided they wanted to go ahead with the flight. The airplane was equipped with a Garmin G1000; Nexrad and Radar. I monitored the weather along our entire flight and everything looked good to beat the storm into our destination. We were lined up on the ILS even though the weather was reporting 4500 and 7. I had ground contact the entire time but it started to rain hard and visibility out the windscreen was less than great due to the rain. I could see the runway lights as we approached and then I was hit by a very large down draft. I went missed; gear up; full props and power and could not maintain altitude. I had to pitch up past 30 degrees and I was able to reach about 2000 ft msl; then I lost the down draft and stalled. I recovered from that stall and reached around 2000 ft msl a second time. This time the plane buffeted and I recovered from that also. The turbulence was extreme and I could barley see my instruments because the plane was shaking so hard. After I recovered from the situation I informed Approach of the severe weather we encountered and we diverted. I am not sure if I hit severe wind sheer or a micro burst but it was all I could do to keep the aircraft flying and maintain altitude. I believe that having the Garmin 1000 system with the Nexrad weather and Radar helped us track the storm but looking back I believe it may have given me a higher sense of security. The speed of the storm must have picked up dramatically as it approached Lake Michigan and also the intensity exploded. These changes in the storm were not picked up by the Radar or Nexrad in time to warn me. I may have kept a further distance if the airplane was not equipped so well. Recent advances in technology help us every day but they may also help us make decisions that we may not have without such equipment. I strongly feel that I made safe decisions with the information I was provided and would have done nothing different at that moment. I never once felt that the approach was putting us in harms way. I do feel however; after the fact; that next time I will keep a much further distance between any storms and my aircraft especially while going into an uncontrolled airport with no wind sheer warning capabilities and storms in the area. Thunderstorms are very unpredictable and should be treated with the utmost respect. I have taken away valuable insight from this situation and hopefully someone else can learn from what I experienced. I also know for a fact that simulator training for these conditions in the BE200 and CE550 is the sole reason I was able to react so quickly to keep the plane in the air.