On two local flights over the holidays the weather dissemination system didn’t exactly work as one might hope. Day 1 – Cessna 172 flight to a small airport about 40 miles to the northwest. Forecast was for great weather: ceiling above 10,000 visibility greater than 6 miles – no mention of snow flurries.
Shortly after takeoff, the ridges to the west took on the distinctly gauzy appearance of snow showers and the higher we climbed, the more the visibility declined. I called Flight Watch to ask what they were showing. “Well the forecast is looking good and although there was some virga reported, no widespread snow. ”
Yes, but looking out my windshield there’s quite a bit of snow and so here’s a pirep of marginal VFR and it could be going IMC over the mountains. “Yes sir but the forecast ….. “ We returned to home base about 15 minutes later. For a good part of the afternoon, there were snow showers that came and went. Not so good for VFR and nice to be inside with a cup of coffee – wishing I were aloft but not in a C172.
Day 2 – Got a full weather briefing for another VFR trip in a DA-40 to another airport – this one about 65 miles north. It was kind of hazy but the sun was up there – shining through . Forecast was for good VMC and even though temperature dewpoint spread was close, the briefer warned of marginal VFR to IMC up north. Aside from the early morning haze that would burn off as the temperature dewpoint separated, what other indications were there? Was there a ceiling that might preclude the sun from heating up the air the way it was forecast? Had there been any pireps? What other information did he have that might invalidate the forecast that good VFR was in the offing in about an hour?
The briefer responded that he had none of those but was still concerned about the conditions. I volunteered to give a pirep once aloft. By the time we got to where the MVFR or IMC had been, it was beautiful day with temperatures in the 50s, no ceiling and visibility 10 miles or better.
Why tell the story? It points out, to me, a weakness in our weather information system. It is not intended to slam the forecasters. In the first case, the weather moved in and reality was much worse than expected. In the second case, VFR not recommended continues to dissuade pilots to fly until they decide to see for themselves and find a perfectly flyable day. Unfortunately, too many become emboldened by the occasionally inaccurate forecast and the understandably conservative approach taken by the briefers. Ignore what happen on flight one and then things can get very ugly indeed. Believe what you’re told on what happened in flight two and you may begin to start ignoring forecasts when the wolf really is out there.
As a famous president once said, ” Trust but verify.” Seems we should be doing that with aviation forecasts.
For more information on this topic check out ASI’s SkySpotter interactive course.