 Local Conditions In gathering weather information for a flight, obtain current  and forecast conditions where flying, as well as alternate  airports in case landing at the intended destination is not  possible. These conditions should include wind (surface and  winds aloft), moisture, stability, and pressure. Surface wind predictions and observations can be looked  at with a number of internet resources. The National  Weather Aviation service provides observations (METAR)  and forecasts (TAF) for areas with weather reporting  capabilities. Winds aloft are forecast winds at higher altitudes than the  surface for locations throughout the United States. Refer  to the Pilot’s Handbook of Aeronautical Knowledge for an  understanding of the winds and temperatures aloft tables.  Winds aloft, too, are important for flight planning and  safety. A typical situation during morning hours is cold air from the  night settling, creating calm winds at the surface with the  winds aloft (300 to 3,000 feet) at 30 knots. As the surface  begins to warm from the sun, the cold surface air starts to  warm and rise, allowing the high winds from above to mix  and lower to the surface. The wind sheer area in between the  high winds above and calm winds below is usually turbulent  and can overwhelm aircraft or pilot capabilities. Therefore,  it is a dangerous practice to look only at the wind sock for  surface winds when there could be strong winds above. Winds  aloft must be evaluated for safe fl ight.  [Figure 5-5] During initial solo flights, the wind should be relatively calm  to fly safely. As experience is gained, pilot wind limitations  can be increased. It is not until the pilot has had dual training  in crosswinds, bumpy conditions, and significant pilot in  command (PIC) time soloing in mild conditions that pilot  wind conditions should approach the aircraft limitations. A  safe pilot understands aircraft and personal limitations. Moisture in the air has a significant effect on weather. If  the relative humidity is high, the chance of clouds forming  at lower altitudes is more likely. Clouds forming at lower  altitudes create visibility problems that can create Instrument  Meteorological Conditions (IMC) in which the visibility is  below that required for safe flight. The temperature-dew point  spread is the basis for determining at what altitude moisture  condenses and clouds form. It is important to be particularly  watchful for low visibilities when the air and dew point  temperatures are within a spread of three to four degrees.  COLD AIR BELOW WARM AIR ABOVE CALM BELOW Turbulence where  the strong winds mix  with the calm air S T R O N G W I N D S A B O V E Figure 5-5. Typical morning inversion layer—calm cold air is below; high winds are above. 5-4