The Weather Never Sleeps

It was a crisp, see-forever Midwest winter day. On Saturday, in his Kansas City hotel room, Dudley Flyright was busily checking his VFR/IFR Low Altitude Planning Chart to plot his route for tomorrow's trip to his next assignment in Oklahoma City. With no wind, the 300-nautical mile trip would take him approximately 2.5 hours.

Because it kept him out of a military operating area (MOA) and offered one more navaid than a more direct route, Dudley decided to fly from MKC (Kansas City Downtown) to OKC (Will Rogers World) via the BUM (Butler), OSW (Oswego), and TUL (Tulsa) VORTACs.

The next morning Dudley looked at the big picture on the Web and the weather had changed. The CNN Interactive forecast for Sunday evening (Figure 1) showed snow and a low-pressure area sitting portentously atop his planned route. The current satellite image showed that clouds, like those outside his window, would also be outside his aircraft window all the way down to Oklahoma City (Figure 2). And the composite radar image showed some light precipitation around his destination right now (Figure 3). This wasn't an immediate turn-off, but it bore further investigation because Dudley was still working on his instrument rating. It also made sense to check out a western route, just in case it looked better that way.

Dudley decided on a 1500 Zulu (9 a.m. local) departure time and downloaded a standard briefing from DUATS. His flight covered two forecast areas - Chicago and Dallas-Ft. Worth. The 4:45 a.m. area forecast [CHIC FA 281045] for the northern half of Missouri called for a 5,000-foot overcast by 9 a.m., occasionally as low as 3,000 feet, with scattered light snow showers. Between 11 a.m. and 1 p.m. (though he'd be nearing Oklahoma before then) the weather was forecast to be 2,500 feet overcast with occasional three to five statute miles visibility in light snow [MO NRN 1/2...CIG OVC150 TOPS TO FL220. 15Z CIG OVC050. OCNL CIG OVC030 WITH SCT -SHSN. 17-19Z CIG OVC025. OCNL VIS 3-5SM -SN. OTLK...MVFR CIG SN]. Like the forecast said, this was marginal VFR weather, and the possible precipitation pushed Dudley's personal weather minimums.

Eastern Kansas generally had a 6,000-foot overcast, with a 4,000-foot overcast by 9 a.m. At 1800Z (noon) the forecast called for a 2,500-foot overcast, occasional three to five mile visibility in light snow and mist, and northerly winds gusting to 25 knots. The forecast also said it was supposed to be VFR by 10 p.m. [KS ERN 1/2...CIG OVC060 OVC150 TOPS TO FL220. 15Z CIG OVC040. WDLY SCT -SHSN NERN 1/4. 18Z CIG OVC025. OCNL VIS 3-5SM -SN BR. NLY WNDS G25KT. OTLK...MVFR CIG SHSN BR BECMG VFR BY 04Z]. Dudley frowned at the even more marginal weather and decided that flying a western route to OKC wasn't the way to go.

The Dallas-Ft. Worth forecast [DFWC FA 281045] offered a little more hope. For the part of Oklahoma he would traverse, the forecast predicted scattered clouds at 5,000 feet with an occasional 4,000-foot overcast with three to five miles visibility in light snow and mist after 7 a.m. (and the same gusty northerly winds). By 4 p.m., the forecast offered scattered to broken clouds at 12,000 feet and a VFR outlook [OK RMNDR...AGL SCT050 BKN120 TOPS TO FL220. OCNL CIG OVC040 WITH VIS 3-5SM -SN BR AFT 13Z. NLY WNDS G25KT. 22Z SCT-BKN120 TOPS TO FL220. OTLK...VFR]. If Dudley made the flight today, he knew it wouldn't be at his planned cruising altitude of 6,500 feet.

The forecast showed no severe weather warnings or SIGMETs, no convective SIGMETs, and no thunderstorms were expected [MKCC WST 281355 CONVECTIVE SIGMET...NONE OUTLOOK VALID 281555-281955 TS ARE NOT EXPD].

Dudley found, however, a ton of AIRMETs - the familiar Sierra (IFR), Tango (turbulence), and Zulu (icing). Dudley didn't like AIRMETs because it took him longer to look up the identifiers than it did to figure out whether the AIRMET affected his flight. For example, the AIRMET for IFR read "AIRMET IFR...ND SD NE KS MN WI IA LS MI OK TX...UPDT FROM 90WSW YWG TO YQT TO MQT TO EAU TO DBQ TO SUX TO TUL TO DHT TO 50W LBL TO 60W LBF TO ABR TO 90WSW YWG CONDS CONTG THRU 21Z."

Instead of looking up the identifiers, Dudley went to the Web page for NCAR real-time weather data (www.rap.ucar.edu/weather/aviation/) to see a graphic of the text. Mentally drawing his two possible routes to these images, Dudley saw that AIRMET Sierra (Figure 4a) would encroach on his westerly route but just touched the easterly one.

AIRMET Tango (Figure 4b) covered both of Dudley's routes, but the text for this AIRMET said it would be moderate below 10,000 feet. If he encountered it, Dudley knew the turbulence would dislodge loose items in the cockpit, so he made a mental note to make sure everything was secured - if he made the flight.

The icing AIRMET (Figure 4c) picture looked good for his route, but Dudley knew never to depend on just one source of information, so he read the AIRMET Zulu text. It wasn't good - multiple freezing levels from the surface to 6,000 feet for his route in Missouri and Kansas. In Oklahoma the text showed occasional moderate rime and mixed ice in clouds and precipitation. [AIRMET ZULU UPDT 1 FOR ICE AND FRZLVL VALID UNTIL 281500 FRZLVL...MULT FRZLVLS SFC-060 ERN 2/3 KS AND WRN 1/4 MO. ELSW FRZLVL SFC-040. OTLK VALID 1500-2100Z...ICE OK AR LGT OCNL MOD RIME/MXD ICGICIP].

Without a second thought Dudley decided that tomorrow might be a better day to fly. Even though he would not fly in the clouds, the forecast called for precipitation. Even without the ice, the marginal VFR conditions of low ceilings and visibility, turbulence, and chance of precipitation stacked the weather deck against a safe and pleasurable flight.

With time to kill now, Dudley browsed through the rest of the DUATS briefing. He stopped at the radar summaries. They showed wide areas of light snow at about 5/10ths coverage around 100 miles west of his route. At OKC, the automated 7:35 a.m. radar report showed a 5/10ths coverage area of light snow 100 nautical miles wide from 007 degrees at 127 nm to 048 degrees at 30 nm. With precipitation was ice, the AIRMET said.

Looking at the TAFs, Kansas City's forecast for 9 a.m. (the time Dudley had planned to take off) said that the wind would be 310 true at eight knots, the visibility would be greater than six miles, the ceiling would be a 7,000 foot overcast, and by 11 AM, light snow and 4,000 overcast. [TAF KMKC 281130Z 281212 25007KT P6SM OVC150 FM1500 31008KT P6SM OVC070 TEMPO 1720 5SM -SN OVC040].

About the time he would have been there, the Tulsa, Oklahoma, forecast for 11 a.m. said the visibility would decrease to five miles, the 3,000-foot scattered clouds would become an overcast ceiling, and light snow would start to fall. Also, between 11 a.m. and 2 p.m. visibility could temporarily be two miles in light snow and mist, with a 1,500-foot overcast. [TAF KTUL 281135Z 281212 20006KT P6SM BKN080 OVC200 FM1400 30009KT P6SM SCT030 OVC060 FM1700 32012KT 5SM -SN OVC030 TEMPO 1720 2SM -SN BR OVC015].

At his destination, the Oklahoma City TAF said that between 8 a.m. and 2 p.m. the weather could temporarily go down to 2,000 broken and two miles in light snow - and it would be windy. Both the 6 a.m. and 2 p.m. times had 17 or 18 knot winds gusting to 33 knots. By 2 p.m. that ceiling was predicted to stay at 3,000 or below [TAF KOKC 281135Z 281212 34017G33KT P6SM SCT025 OVC090 TEMPO 1420 2SM -SN BKN020 FM2000 34018G33KT P6SM BKN030 OVC080 TEMPO 2023 3SM -SN BKN020].

The TAFs reinforced Dudley's decision to stay in KC. In business, fortune favors the audacious, but Dudley knew there wasn't any Chapter 11 option available for aeronautical stupidity, so he elected to live and fly again another day. Tomorrow, more than likely, would probably be better, smarter, and safer.