Dudley had gone over his St. Louis and Cincinnati sectionals in advance and had chosen an easterly heading from the Capital Vortac along the V50 airway to the Decatur Vortac, then across the Wabash River to the Terre Haute, Indiana, Vortac. He'd have to jog between three airways before reaching the Cincinnati Vortac, located in northern Kentucky, just southwest of Cincinnati. The terrain was fairly friendly, and there was no shortage of landmarks to check his progress.
For the final 135 miles, he would have to travel south on V128 to avoid a large military operations area, then take V493 north toward Jackson, Ohio. From there he would follow a highway right to Ohio University. His route would cross military training routes no fewer than seven times, but they were all for operations at or below 1,500 feet above ground level, well below his cruising altitude.
Handling the weather, however, might not be so straightforward. A huge low pressure system had just brought snow to the Great Lakes and upper Midwest, although it was moving east now with high pressure behind it on its way from the west. When Dudley got to the airport at about 9 a.m., there was a foot of snow on the ground, only one of the runways was open, the winds were 16 knots gusting to 23 knots, and the clouds were moving like freight trains overhead.
It took Dudley just two minutes to scan some two dozen charts, images, and text pages on the DTN screen. The first thing he looked at was the infrared satellite image of the United States, which had an accompanying audio briefing synopsis as well as animation showing the last few hours of cloud movements. The heavy snowfalls in Illinois and Indiana were forecast to move northeast into Canada, with near-blizzard conditions in Michigan and western New York. Cold air was expected to plunge down the plains from Canada behind that low pressure system, bringing high winds.
Next he looked at the latest 12-hour surface forecast, which depicted an area of snow showers within a larger area less likely to have snow. The border between these areas was right along his planned route.
The next chart that got his attention was the Ohio Valley radar, which showed a large area of light snow along his route through the Indianapolis area. Remembering those fast-moving clouds, he looked at the northeast regional winds aloft plots for 5,000 feet msl or FL050 (Figure 4) and 10,000 feet msl (FL100) on either side of his planned 7,500-foot altitude. The winds at 5,000 feet averaged 30 to 35 knots and reached 50 knots at 10,000 feet. And, for once, they were tailwinds.
Now it was time to get down to the details of the weather for this trip. The next thing Dudley had a look at was the DUATS "Quick Path" briefing data, available via modem from the DTN unit. Central Illinois had 1,500- to 2,500-foot ceilings, cloud tops to 16,000 feet, three to five statute miles visibility, and light snow with a marginal VFR (MVFR) outlook.
Conditions in Indiana were about the same, while in Ohio the ceiling was overcast at 2,000 feet with cloud tops to 8,000 feet and three- to five-mile visibilities in light snow. The forecast was for broken clouds at 3,000 feet by midday. Airmets had been issued for both Chicago and Boston for occasional ceilings under 1,000 feet, visibility under three statute miles in snow showers, occasional moderate turbulence, and occasionally moderate rime and mixed icing.
The aviation routine meteorological reports (METARS) showed marginal VFR at best at most airports along the way, but there were two pilot reports (pireps) listing cloud tops at 5,000 and 5,500 feet near Indianapolis and Cincinnati. The pirep for Indianapolis also reported light rime icing, while the second reported no ice.
Dudley gave up all hope for an early departure when he read the terminal aerodrome forecasts (TAFs). The most recent TAF for Springfield predicted a 2,500-foot overcast until 11 a.m. with temporary visibility at four statute miles in light snow. The ceiling was expected to drop to 2,000 feet and eventually to 500 feet with only one mile visibility between 1 p.m. and 5 p.m. It was about the same for Decatur, 40 miles east. At Terre Haute, about 100 miles away, he might find a 2,000-foot overcast. Indianapolis predicted a 2,000-foot overcast and light snow between noon and 4 p.m. Cincinnati was calling for about 2,500-foot ceilings, and no less than five miles visibility.
The winds aloft at Springfield, Indianapolis, and Cincinnati were all about 30 knots, right on the tail. That was sweet, but notices to airmen (notams) for the destination airport called for unreliable wind data and "thin-packed snow on runway, braking action poor." At this point, Dudley decided that his brakes were working just fine, and he was staying put. What if the forecasts were just a little bit off, say the ceilings were 1,000 feet lower, or visibility two miles less? He decided to wait it out. The thrill of ground speeds exceeding 150 knots carried too high a risk.
After lunch, Dudley checked the DTN terminal again. The Northeast Sky Conditions chart showed that the snow and freezing rain were still around. The 12-Hour Low Level Significant Weather Prog chart indicated that things were not likely to get any better today.
Five METARs issued for Springfield within the last 25 minutes reported ceilings varying between 2,200 and 3,400 feet, with visibility ranging from one-half mile to five miles. Champaign/Urbana and Decatur both had under two-mile visibilities and ceilings of 1,800 to 1,900 feet. The Indianapolis tower was reporting variable visibility, and another local automated observation gave values as low as three-quarters of a mile visibility and 1,100-foot ceilings. These were mostly worse than the earlier forecasts for both ceiling and visibility. And that was all it took to make Dudley deeply grateful that he'd stayed on the ground at Springfield. There's always another day.
For more information about DTN weather services, call 800/610-0777; AOPA members can visit AOPA's online weather, which is provided by DTN ( www.aopa.org/members/wx/).
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