WARNING – What follows ends with a totally shameless unsolicited advert. for Scott Dennstaedt’s “Weather or Not” weather seminar.
Yesterday I got a last-minute call to fly an Angel Flight mission from Raleigh, NC (KRDU) to Bristol, TN (KTRI). The general area forecast for western NC and eastern TN was iffy at the time, so I told the mission coordinator I’d check the weather more carefully and call her back if the flight was doable. A detailed look at the forecast weather indicated it would improve significantly, with the rain stopping and the cloud cover breaking up overnight. High winds / occasional light to moderate turbulence at low altitude would be the only real issue, so I accepted the mission, intending to file for 9-12K ft enroute. This morning, the weather out the window was nothing like the forecast - solid low overcast instead of broken to scattered, and it had snowed 4 inches here in the western NC mtns. The forecast for the Raleigh area was still good, but the new “official” forecast for KTRI had low overcast, light to moderate snow and significant icing in clouds below 6K ft MSL. Humm, I thought, a NO-GO decision has to be made. Too bad about the sick child who needed transport.
Before calling the mission coordinator, I decided to use the tools --especially the Skew-T plots-- Scott taught us in his course to see if the new forecast might be too pessimistic. After all, it was much worse than the “official forecast” from only 8 hours earlier! Sure enough, the plots indicated that by my arrival time (1330h EST) the cloud bases should be about 2500 msl with the temp about 5 C, and the tops should be about 5000 msl with the temps about 10 C. In the clouds, the temps would be right in the ice accumulation critical range, but the layer was only 2500 ft thick. I could stay high in the clear until on the localizer, then dive for the glideslope intercept at 3600 ft msl, keeping my time in the clouds down to only about 2-3 minutes. If other arriving traffic reported bad icing on the ILS apch or ATC balked at my plan, Plan B would be to continue in cruise to the PAXs’ next pick-up point in northern KY, by-passing the 2nd leg pilot altogether, and have flight service contact that pilot to abort his leg of the trip. Plan C would be to divert to KHKY, my home base airport, and drive the pax to KTRI (only about a 2 hour drive by car and I have 4-wheel drive and chains for the mtns). So, I kept the mission. Of course, we fought headwind components as high at 68 kts all the way from RDU to TRI, but the ride was smooth - surfing the slow oscillations of the mtn waves at 8K msl.
Upon arriving in the Bristol area, PIREPS indicated the RUC Skew-T model was right on. Tops were at 5500, temp 8C. Bases were at 1800 agl (3100 msl), temp +3. Earlier arrivals had reported trace to light rime ice from the clouds tops down to 3500 msl, but according to the apch controller the “last 1/2 dozen” had reported negative ice. I told the controller about my slam-dunk plan, he agreed, and down we went. No ice, smooth as glass. The patient got where he needed to be because I knew enough to “look for myself” instead of blindly following the Flight Service briefer’s gloom and doom prognosis. (The 2nd leg pilot had a nice all-weather Malibu waiting…).
So, those of you who haven’t taken Scott’s class, or don’t think you could get anything useful out of it, think again. Why sit on the ground all winter when a little more independent information might make a world of difference? 'nuf said.