Weather Briefings

INSTRUMENTS FLIGHT PLANNING

CHAPTER SEVEN

Next, check both the existing and forecast local weather for your estimated time of departure.

Check the bases and tops of cloud layers, freezing level, crosswind, and runway temperature or

pressure (density) altitude, when required. Do not neglect T/O weather in flight planning. If the

local weather dictates, plan for the measures that must be taken to prepare the aircraft for entry

into freezing clouds, such as pitot heat, engine inlet anti-ice, etc. On days when the weather is

below available approach minimums, discretion requires a plan for a suitable T/O alternate

airport where you can land safely should an emergency occur after T/O. A minute of planning

for this possibility may pay rich dividends later.

Enroute

Check the winds along the route of flight through a considerable range of altitudes. This allows

the selection of the best altitude for aircraft performance, and gives you a feel for the change in

aircraft performance you can expect if you are given a change in altitude enroute. Look

specifically for the extent of clouds that may be present along the proposed route. Check the

altitude of the tops and bottoms of the clouds. When clouds are present and flight is conducted

on instruments along the route, keep in mind the location of the nearest area that is VFR for

letdown and landing in the event of complete radio failure or other emergency.

You must carefully ascertain the possibility of any hazards to flight along your proposed route.

Know the altitude of the freezing level and the likelihood of icing. Do not plan a flight for

extended periods in clouds with a temperature just below freezing for this is the level of

maximum icing. Check for the likelihood of thunderstorms and turbulence and avoid them

whenever possible. If avoidance is not possible, plan to minimize their effect. The presence of

fog, low ceiling, and low visibility areas along the route are additional hazards. Know the

location of these areas before leaving the weather office. A look at the Weather Depiction Chart

or the sequence reports discloses areas that are near or below IFR minimums.

Destination

You must know, in detail, the weather to be expected at your destination. If the weather is

forecast to be IFR, analyze it closely, then carefully choose the alternate(s). Look for ceiling and

visibility, precipitation; amount of snow, if present; RCR or equivalent runway braking action;

forecast wind and the likelihood of crosswinds to the runway; the effect of surrounding

topography on weather conditions at the field, etc. Check on the possibility of a delay in landing

due to the presence of heavy showers or squalls at the destination. Always try to choose an

alternate with better weather than the destination.

703.

WEATHER BRIEFINGS

Before obtaining a flight clearance, you must receive a verbal weather briefing in person, by

telephone or by weather vision. Additionally, a DD 175-1 (Flight Weather Briefing Form) is

completed for all IFR flights. The verbal briefing contains a detailed analysis of present and

forecast weather in the immediate vicinity of the departure point, along the flight route, and at

the destination and alternate airfield(s). All potential hazards to flight are included.

IN-FLIGHT WEATHER ANALYSIS 7-3