3 min read

Today is one of those “in between” days, which are frustratingly common in flying. The weather isn’t great, with some rain and potential in-flight icing, but it’s not terrible either, and you fly a well-equipped airplane. The proposed mission today is to fly from your home in Bismarck, North Dakota, to Billings, Montana, the first leg on a five-day tour of the Western United States in support of your business. Your Piper Turbo Aztec is well equipped for IFR missions in the West, with a cruise speed over 200 knots, built-in oxygen, and deice boots. The flight should take just under two hours—if you can go.

Planned departure time is 2030Z. Read the weather briefing below, then add a comment and tell us what you would do. Go or no go?


The map in ForeFlight shows no major lines of weather, but there’s definitely some rain over eastern Montana, right along your route.

Looking at the surface analysis, there are no major fronts in the area, but it seems like there’s some type of minor disturbance.

The prog charts show some rain and storms developing over the next 24 hours, slowing moving east.

Radar and satellite

Job one is to understand whether that rain is just rain or something more serious. The regional radar image shows a very scattered area of cells, but some of them do look to be convective.

The infrared satellite backs up that theory, showing some clouds with vertical development.

Finally, a look at the visible satellite suggests there might be a path through the build-ups in North Dakota, but probably not once you get into Montana.

There is a convective SIGMET outlook in the area, but the actual SIGMETs are well north and south of your route.


In addition to concerns about thunderstorms, it looks like in-flight icing is likely. A look at the freezing level chart shows you’ll almost certainly be flying below 0 degrees at a typical cruise altitude of 10-16,000 feet.

Icing forecast charts show a good chance of ice, starting at about 9000 feet.

The threat of icing seems to be fairly consistent up into the teens today. You might get above it by 22,000 ft, but that’s a lot higher than you like to fly.

The AIRMET for icing backs up this forecast, with moderate ice predicted over much of your route.

The cloud forecast map shows fairly high bases, but tops are above FL250 in eastern Montana.

Text weather

Finally, some good news. The weather at your departure airport is good VFR and is forecast to stay that way.

En route weather reports are showing good VFR, with that fairly high ceiling.

Your destination is also reporting good VFR, and the TAF looks favorable.

Decision time

It’s time to make the decision. The weather at your departure and destination is quite good, and you fly a very capable airplane. But there is definitely some work to do en route if you decide to launch, including possible icing and thunderstorms. You could try to go low, and stay out of the clouds, or you could try to go high and get on top of the ice. Then again, you could cancel and play it safe.

What would you do? Add a comment below.

John Zimmerman
9 replies
  1. Ethan
    Ethan says:

    I would do this flight, but only because the turbo Aztec has a turbo and oxygen. I would file an IFR flight plan but depart VFR and take a look see at the extent of the vertical development and placement of the cells. If I could thread the cells VFR with plenty of clearance I would continue VFR. If it looked like the cells were too packed together and too high, I would climb to 17,500 and see if that topped the cells. If I needed higher, I would pick-up IFR and climb to on-top. The weather at the destination could present additional problems so I would pick a good alternate.

  2. Gary
    Gary says:

    Having only 600 hours under my belt and only a VFR rating I would not go. I had a 172/180 horse, well equipped, Garmin 430, auto pilot, etc. I had the full IFR training but never took the final test. My motto was always “there will be another day.” Being retired has the advantage of not worrying about the mind set of

  3. Danny Kao
    Danny Kao says:

    Without radar I would be reluctant to pick my way through weather to avoid the cells. Flying above the weather is a possibility, but FL 220 in an unpressurized aircraft is not for the faint of heart. I’d go high if the Aztec’s heaters work well – it’s COLD up there. I’d also liberally IceX the boots and only go if there’s very low probability of SLD.

    More likely, I’d go VFR and stay low to avoid the clouds with plans to land and wait out the weather as Plan B.

  4. R
    R says:

    Couple of options (in order of preference):

    1 a couple of days later when the wx has past (bet the high to the west brings easier conditions)

    2 VFR at low alt where temps>0*, ability to visually avoid precip and maintain safe descent/divert options.

    3 start high/IFR and be prepared to stop or turn around immediately upon clouds tops exceeding a safe/planned cruise alt.

    No way (turbo and boots not withstanding) that I would want to find myself in cloud top icing conditions that I couldn’t out-climb!

  5. Duane Mader
    Duane Mader says:

    I’d go and stay low. No ice. Avoid areas of precipitation below bases and figure on deviation south of course (as long as Powder River MOA isn’t active). You’re not going to get high enough to top any actual thunderstorm cells in that and you’re probably not getting high enough to even top the general cloudiness and get a look. If you go up over the mess you’ve got to come down through it.

  6. Terry Spath
    Terry Spath says:

    Last Friday I flew the Company King Air 250 from Casper to Helena. Turbulence was continuous light with occasional moderate at FL280. I fly 300 hours per year in this plane in Wyoming, Montana and the northern Rockies. I’m almost always in the flight levels and feel pity for the piston pilots that are down low getting beat up in turbulence, especially in the afternoon when there’s vertical development.

    In my career I’ve flown on three continents and the severity and duration of turbulence around these parts exceeds anywhere else I’ve flown. Several flight attendants have been injured in airliner cabins on the descent into Billings over the years because of turbulence.

    Knowing all of the above I would say an afternoon flight even in a turbo’d piston will probably be unpleasant. I think I’d wait until the next morning. In my experience, turbulence in this part of the country is the challenge. Icing certainly is an issue but not to the extent as it is in maritime climates like west of the Cascades in Washington.

  7. José Serra
    José Serra says:

    Conservative as I’m in flying respecting, I wouldn’t go, nevertheless the oxigen and turbo installed in the Aztec

  8. Larry Baum
    Larry Baum says:

    Having a turbo Aztec with 02 and boots give the pilot a lot of vertical options. The pilot qualifications and proficiency isn’t mentioned. So assuming that the pilot is as capable as the plane, this flight is a go. A bit bumpy at any altitude. Key will be to stay out of the ice, so staying out of IMC might make going low a bit more favorable than getting on top. With the weather on departure, getting up on top seems plausible as well. Can always descend if there’s ice.

  9. Michael G holmberg
    Michael G holmberg says:

    I would probably go but I’m an old freight dog. Many flights without on board radar and minimal de-ice protection. Depended on ATC for weather avoidance.


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