I knew the trip West after AirVenture from Green Bay, Wisconsin, to North Big Horn County Airport (U68) in Cowley, Wyoming, would bring this flat-land pilot closer to mountain peaks than I'd been for a while and require some changes in my normal operating procedures. With MEAs (minimum en route altitudes) over the Black Hills and the Big Horn Mountains as high as 12,000 feet, there would be a potential for ice in any clouds even in August, so I'd be more comfortable flying VFR on the last leg from Rapid City, South Dakota. If there was any weather over the mountains I'd be between a rock and a hard place, so I was careful to leave plenty of slack in my schedule.
What I hadn't anticipated was that on the first leg from Green Bay to Sioux Falls, South Dakota, while there would be no "rocks," there would be two "hard places" between which I'd have to thread my way. During my preflight weather briefing, the flight service specialist warned me of sigmets for severe storms that scribed wide areas both north and south of my course. I decided, since the weather at Green Bay was good and either a return or diversionary landing along the route were viable options, to go ahead and at least begin the trip.
The sigmet-ed storm south of my route was the closer one and it looked, from the WSI NexRad display on the MX20, that once I had eased past the brunt of the southerly system, I'd be able to angle southwest toward Nodine (ODI), the VOR just west of La Crosse, Wisconsin, and stay in the middle of the corridor between the two storms.
I wasn't the only one trying to stay out of the weather. There was a VFR pilot on the frequency who was getting lots of help from the controller in his effort to get through the area without getting slammed around too much. I didn't envy him. At least I could see where the storms were-or had been only minutes earlier. Using the Stormscope as a backup, I was reassured there was nothing lurking in the clouds with me to cause a slam dunk!
As I got closer to the storms, my planned deviation, based on the direction and speed of the echo tops, appeared to still be a reasonable path down the gulch between the storms.
Once I passed the storm to my south, I called the controller and requested a deviation direct to ODI and then direct to Sioux Falls. You can imagine my reaction when the controller came back with: "Unable to approve the deviation because of military activity. I can't approve a deviation from your present position."
Without the deviation, my course was taking me directly into the maw of the second storm. The WSI was indicating that the tops were at 50,000 feet, there was large hail and the path of the storm was to the southeast.
"I'll need a deviation as soon as you can approve it," I told the controller. The situation was not yet critical, but it was time to begin considering my alternatives.
As I approached my time-to-make-a-decision point based on my distance from the storm, I called the controller again. "Any chance of deviating 20 degrees to the left?"
"Deviation of 20 degrees is approved and I can let you deviate anywhere you want in about five miles."
I ended up a lot closer to the storm than I wanted to be. It turned out that the deviation to ODI wasn't going to keep me clear and I had to swing farther to the south than I had expected, but I was able to skirt the storm and turn back toward Sioux Falls and clear skies.
It was an interesting lesson. It's been rare that I haven't been granted a request for a deviation when I've needed one. The possibility that a request might be refused injects another prudent consideration into weather avoidance planning. I was recently reminded of another lurking gotcha. Doug Stewart and a student, during an instrument approach on one of his 'Narly New England training flights', had to execute a missed approach when the student broke out high and fast. But they found because of the mountainous terrain in the area, that their only option was to fly the published missed and it required them to fly much closer to a cell than they wanted to. The cell hadn't been in their path during the approach, but became a concern during the missed. We're often so set on getting on the ground, we neglect to consider what might be in our path if we do have to execute a missed approach.
