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Preflight Weather-What to expect from Flight Service

by Julia Greenway
Reprinted with permission from FAA Aviation News

NTSB reports available through NASDAC (National Aviation Safety Data Analysis Center) from January 1,1996, to December 31, 2002, indicate that over 50% of the pilots involved in Title 14 Code of Federal Regulations part 91 fatal weather accidents failed to obtain a required weather briefing. A further in-depth review of these accidents shows that they could be classified into four broad categories related to weather hazards and weather information:

  • The weather hazard is unknown to the science of meteorology.
  • The weather hazard is known but not detected or reported to aviation weather dissemination outlets.
  • Aviation weather dissemination outlets fail to advise the flight crew of a weather hazard in a timely manner. Weather hazard areas frequently pose a time critical need for information and action by flight crews. This is a common failure. The data show a very limited number of weather updates on in-flight weather briefings.
  • The weather hazard is understood, detected, and disseminated; however, the flight crew lacked the knowledge, skill, ability or judgment to effectively deal with the weather hazard.

Much of what we do at Flight Service involves these very crucial elements of flight and timing of information. At Flight Service, it is our responsibility to provide weather and aeronautical information to the pilot in a sequenced and easily understood format, with explanations as required and requested. It is the responsibility of the pilot to provide the minimum information requested and to understand and comprehend all information to make an informed decision to fly.

As a Flight Service specialist, I understand that knowing what to look for in weather patterns is essential to a safe flight and providing that information into an easily understood weather briefing can only translate into aviation safety. No one will argue that this is an easy task, as no one will argue that weather is an exact science. One that is not easily predicted, even with good forecast data; but deciphering weather along changing terrain and weather patterns and translating that into an understandable format is a challenge within science itself'a challenge that is shared by both the pilot receiving the service and the preflight weather briefer providing the service.

VFR Flight Not Recommended

VFR Flight Not Recommended (VNR) may be the most controversial statement in Flight Service. However, Flight Service specialists are required to include this VNR statement to the pilot 'when VFR flight is proposed and sky conditions or visibilities are present or forecast, surface or aloft, that in your best judgment would make flight under visual flight rules doubtful.' Further, the specialists are required to 'describe the conditions, affected locations and times.' If a briefer tells you that VFR flight is not recommended without providing an explanation, or the explanation is not obvious, and you are not sure why VFR flight is not recommend, ask the briefer for the reasoning behind the recommendation. VFR may not be recommended in a certain area, because of low visibilities, but may be completely unrestricted in another direction, allowing for VFR flight. The important thing to note is that this recommendation is advisory in nature, and the final decision as to whether the flight can be conducted safely rests solely with the pilot. The briefer is required to provide the pilot with the information needed to make an informed decision. Therefore, you should never leave a briefing without a complete understanding of the briefing and recommendation, and if you do not understand any aspect of the briefing ask for clarification or an explanation. Keep in mind, that at a minimum, FAA regulations require the Flight Service specialist to use the VNR statement if: Sky conditions or visibilities are present or forecast, surface or aloft, that in the judgment of the AFSS/FSS briefer would make flight under visual flight rules doubtful.

Remember, just because the briefer does not issue the VNR statement, does not mean a flight will be free of adverse weather phenomena. Thunderstorms, turbulence, icing, and strong winds, do not, in and of themselves, require the briefer to issue this statement. However, these weather conditions usually accompany less than VFR conditions.

Flight Service specialists are qualified and certificated by the National Weather Service as a pilot weather briefer. They provide around the clock real-time weather and aeronautical information mostly to the general aviation pilot. Before calling, it is helpful to check out your local weather station or other media to get a visual weather picture, but keep in mind this is a forecast for land dwellers and should never replace an aviation briefing. Another pre-briefing source of weather, provided by Flight Service, is the telephone information-briefing service (TIBS). This service provides pilots with a recorded summary of pre-determined areas and routes spanning out in different directions from the associated Flight Service Station. Recordings are updated hourly and as significant conditions dictate, but because they are time specific, they are not a good source in rapidly changing weather systems, and should never replace a pilot weather briefing'only enhance it.

Specialists translate and interpret available charts, radar, forecasts and national weather service reports directly into terms describing the weather conditions you can expect along your flight route and at your destination'from surface charts depicting prevailing weather systems to lifted index charts indicating the stability of, or instability of air, to visible satellite imagery depicting cloud 'street' formations (for soaring pilots) to less visible coastal advection fog. Specialists must obtain minimum flight information for the briefing requested and are obligated to provide adverse conditions, both meteorological and aeronautical (your destination airport may be closed), to ensure you have the information you need to make a fully informed decision to fly.

OASIS Equipment

Some Flight Service Stations are equipped with the latest that technology has to offer. Approximately 16 Flight Service Stations are equipped with OASIS (Operational and Supportability Implementation System). OASIS enables the briefer to overlay a route of flight using multiple charts for more precise route weather interpolation, and the latest software includes sectional charts. Other useful features allow multiple weather charts to be displayed at once with continuously updating data.

Minimum Flight Information

It may seem tedious, but be prepared to provide the briefer with the following required information (see Chapter 5 in the Aeronautical Information Manual, AIM) along with your request of a standard, abbreviated or outlook briefing:

  • Type of flight: IFR or VFR
  • Aircraft identification or pilot's name (the briefer needs to create a record file)
  • Type of aircraft and performance enhancements (if applicable, i.e. deicing equipment, radar or storm scopes)
  • Departure point
  • Route of flight
  • Destination
  • Flight altitude(s)
  • Estimated time of departure (ETD) and estimated time en route (ETE)

It is also good to give your pilot qualifications (e.g., student, newly instrument rated), so that the briefer has a better understanding of your experience level to provide you an even more tailored service. There are three types of briefings available and it is best to know which kind you need before calling. However, depending on weather conditions and pertinent NOTAMS, your briefing may dictate more or less information than initially requested.

Standard Briefing

A standard weather briefing is a full weather and aeronautical information briefing, and consists of the following information provided in this sequence (see Chapter 7 of AIM):

  • Adverse Conditions
  • VFR Flight Not Recommended (VNR)
  • Synopsis
  • Current Conditions
  • En route Forecast
  • Destination Forecast
  • Winds Aloft
  • Notices to Airmen
  • ATC Delays
  • Request for Pilot Reports (PIREPS)
  • EFAS (inform pilots of availability of En route Flight Advisory Service for weather updates, thunderstorms, icing, requests for pilot reports, etc.)
  • Upon request items (military training routes, military operation area, military NOTAMS, GPS RAIM information, etc. and any other requests for information)

Abbreviated Briefing

Request an abbreviated briefing to:

  • Supplement mass disseminated data
  • Update a previous briefing, or
  • Request specific information.
Along with specific information requested, provide the briefer with the time, type, and source (vendor, another Flight Service, etc.) of information or your last briefing, and the briefer is obligated to advise the pilot if adverse conditions are present or forecast. Adverse conditions are not just weather related, but include airspace restrictions, ATC delays, and unscheduled airport closures, and any information that may immediately effect your decision to fly. In an abbreviated weather briefing, the briefer will ask if you have received any adverse weather condition reports. Unless specifically requested or the pilot indicates he or she does not have adverse conditions, details are provided only at the pilot's request, and since weather conditions change rapidly, it is strongly advised that you ask for the most current adverse conditions. For example, in summer, convective sigmets are updated with rapidly developing thunderstorms, or conversely, in winter, a pilot report of icing at or near your altitude may become available before or during or after (happens quite frequently) the briefing. This new information may indicate conditions not previously forecast that may be extremely pertinent to your flight. It is crucial to update and stay updated on adverse conditions.

Note: If you request only to file a flight plan, the Flight Service specialist is required to ask if you have the latest adverse conditions along your route of flight. Please do not take this question lightly, as it may mean the difference between a go and no-go decision. And the decision to request details on adverse weather conditions lies solely with the pilot.

Outlook Briefing

An outlook briefing is provided when the proposed departure time is six hours or more from the time of the briefing. The briefing will be conducted in the sequence of a standard weather briefing, but will be limited to forecast data applicable to the proposed time of flight. The Flight Service specialist omits the VNR statement, current conditions, winds aloft, and NOTAMS, unless specifically requested by the pilot or deemed pertinent. Outlook briefings can be obtained, within reason, days before the proposed flight, and updated as necessary. However, Flight Service specialists only receive forecast chart information available within 48 hours of proposed time of flight.

800 Numbers and Cell Phones

Roughly 80 percent of Flight Service specialists' job is pilot weather briefing'primarily associated within the stations in and adjacent to their own geographical area. Within this area, Flight Service specialists are very familiar with the interactions of weather and local terrain. This is why it is important, when traveling across country, to contact the local Flight Service Station in the geographical area that you are departing from. When using cell phones, remember that 1- 800-WX BRIEF (1-800-992-7433), which is the national toll free number for Flight Service, will route you to the local Flight Service Station of your cell phone area code. A popular story is of a pilot on the South Pole (Antarctica) calling Northern Virginia for a local weather briefing. More common, are pilots calling by cell phone in Alaska reaching someone in the contiguous U.S. and requesting a local weather briefing. Obviously, since weather and local terrain are a significant part of flight, it is important that you speak to a briefer familiar with the weather where you are at rather than your cell phone area code.

Toll free numbers (866 numbers) for in-area Flight Service Stations are located in the Airport/Facility Directory (AFD), and may be posted at your local airport. Some Flight Service facilities have dedicated web sites that list helpful information.

Waiting Times

One of the biggest complaints received from pilots at some Flight Service Stations is the telephone waiting or holding times when calling for a preflight weather briefing. It has become particularly challenging in places like Washington DC, because of the Air Defense Identification Zone (ADIZ) and the Flight Restricted Zone (FRZ), among other flight restrictions. Although procedures have settled somewhat in the past months, the waiting times have changed dramatically, mostly due to Temporary Flight Restrictions (TFR), ADIZ restrictions and the resulting increased number of calls. A clear, fair-weather day use to be a breeze for pilots as no flight plans were required, and fair-weather briefings were quickly provided. Now everyone still wants to fly in these areas, but pilots are required to comply with the latest restrictions. Caller off-loads have eased some of the waiting at times, but workload and staffing needs are still not in balance. Flight Service specialists appreciate the patience of the general aviation pilot, and any suggestions to ease this situation might prove helpful.

Weather Briefing

A Flight Service specialist is trained to interpolate and blend real time weather products seamlessly to provide you with the most accurate and understandable weather along your route. They have, at their fingertips, a multitude of weather and aeronautical information from which to draw, not the least of which is their seasonal experience.

Before starting a work shift, briefers familiarize themselves with all available weather and aeronautical information pertinent to their own geographical and adjacent geographical areas, to get the 'big picture.' Specialists normally start out by familiarizing themselves with the local and outlying weather (the big picture)'by using all available charts, radar, satellite, and National Weather Service (NWS) products reporting real-time and forecast weather. The surface analysis chart provides a good basis from which to draw, as it indicates the position of surface based weather systems: such as areas of high pressure, low pressure, fronts, and troughs.

Mental notes are made of anything significant or unusual to pass on to pilots for their shared information and understanding. If something doesn't make sense, like a pilot report for icing, but there are no indications of precipitation on radar, the briefer will check all available data to evaluate the pilot report. There could be a warm layer aloft (inversion), interacting with a weak trough, which working together, can create enough moisture to produce an area of light icing aided along by the upslope of local terrain'or it could be an old (the better part of an hour) pilot report based on the leftovers of an exiting weather system. Since there are sometimes combined (weather is constantly changing) logical answers to real-time weather, there are combined multiple reasons, and the most logical explanation is sought, supported by real-time weather information. As pilots, it is extremely important to key in on any inconsistencies between forecast and real-time weather and the 'why and how' that will affect your route of flight. This is not the time to hold back questions, but to ask until you are satisfied and comfortable with the information provided so that you can make an informed flight decision.

Once a pilot provides the briefer with pertinent background information, the briefer will provide the requested briefing in the appropriate format. Adverse weather conditions are most important, as they may determine the go/no go decision, and include both aeronautical and meteorological information. Adverse weather conditions, the VNR statement, if applicable, and a route synopsis should work together to provide an overall 'big picture,' and should provide the pilot with a solid basis for the rest of the briefing. Conversely, current conditions, pilot reports, and winds should clarify and validate the adverse conditions, VNR statement and synopsis.

Next, the briefer will summarize pertinent current conditions, en route, and destination weather using all available data, NWS data, radar, and pilot reports, and applicable forecast data will be summarized. Individual reports will be read for emphasis only, or as requested. These reports should complete the overall synopsis, VNR statement, and adverse conditions. At any point, the briefer may emphasize significant weather or NOTAM information. It is very important to ask questions if you are not certain how provided weather or aeronautical information pertains to your route of flight.

If you request a standard briefing, current conditions may be omitted if the proposed departure time is more than two hours from the weather briefing. A terminal destination forecast is given for the destination airport. If no terminal forecast data is available for the destination airport, the briefer will provide the area forecast as a destination forecast, supplemented by surrounding terminal forecasts as needed. Remember, that area forecasts are given in heights of mean sea level (MSL), unless otherwise stated by ceiling (CIG) or above ground level (AGL). Terminal forecasts are in AGL. Area forecasts are given in MSL heights to account for the larger forecast area and terrain. Destination forecasts/ area forecasts are provided within one hour before and one hour after your ETA.

Winds aloft forecasts will be given using the compass degree from the direction the wind is blowing, e.g. 'winds along your route of flight are forecast from 340 degrees at 25 knots.' Forecast winds aloft are given in terms of true north, south, east and west, as opposed to magnetic direction, because magnetic north varies from true north depending on where you are located on earth. You must make corrections depending on your geographical location. This information may be supplemented with a pilot report, which should always mesh with the briefing being provided.

All information provided should flow seamlessly from the weather and aeronautical data. Further, the briefer is required to request pilot reports and advise pilots of the availability of radio or Flight Watch for updated briefing or pilot reports.

Airspace Restrictions

Airspace restrictions are spelled out in a NOTAM. Flight Service specialists translate the complexity of the NOTAM as it pertains to your route and altitude of flight. All pertinent NOTAMS are provided in a standard weather briefing. Since pertinent NOTAMS, such as airspace restrictions, airport closures, and ATC delays, may affect your go/no go decision, they are provided as a flight advisory; and in an abbreviated briefing, the briefer will ask if you have the most current flight advisories, including airspace restrictions' if you say yes, details are only available on request. Regardless of the type of briefing requested, changing airspace restrictions, NOTAMS, and advisories can change at any time and without notice'and it is the pilot's responsibility to obtain and understand the latest pertinent NOTAM information through a preflight briefing, and stay updated.

When it comes to flight restrictions, some geographical areas are particularly challenging, especially since changes can occur without warning. With spring coming, snowbirds returning, fun fly-ins, and the many other warm weather activities, it is best to prepare for and understand, well in advance, airspace restrictions along your route of flight. For example, when flying from the New England region to Florida, it can be very challenging to find a place to refuel in the mid- Atlantic area. To operate within the Washington ADIZ, you must be on an active IFR flight plan or file an ADIZ flight plan (IFR for transponder purposes), receive a discrete transponder code, and remain in continuous two-way communication with ATC before entering, landing, or departing the ADIZ. And, the difference between the already small unrestricted area between prohibited area 40 (P40) in Maryland and the Washington DC Metropolitan Area ADIZ narrows considerably, sometimes extending into the ADIZ, when P40 is 'super-sized, 'restricting flight altogether. In fact, just ask, 'Are there any airspace restrictions along my route of flight?' Then, be prepared to copy. Military or U.S. Customs aircraft may intercept aircraft operating within the ADIZ without prior authorization.

To operate in the ADIZ, your transponder must be a coded beacon transponder, the aircraft equipped with automatic pressure altitude reporting equipment, having altitude- reporting capability that automatically replies to interrogations by transmitting pressure altitude in 100- foot increments, and pilots should be knowledgeable of intercept procedures as outlined in the AIM.

In-Flight Services

Flight Service provides two in-flight services: Radio and Flight Watch. Radio, or for example, 'Leesburg Radio,' correlates to the local servicing Flight Service Station'Leesburg AFSS. The common radio frequency nationwide is 122.2 MHz. However, most Flight Service Stations have frequencies discrete to smaller areas within their area. For example, when flying in the Charlottesville, Virginia, area, it is preferred pilots use 122.65 MHz instead of 122.2 MHz to ease frequency congestion, and it is a good idea to obtain discrete frequencies along your route prior to flight either from charts or from your Flight Service specialist, especially if operating in areas of limited coverage.

Radio services include updating weather and aeronautical information; activating, closing or changing flight plans; broadcasting weather updates; and emergency services. Additionally, in some geographical areas, pilots can contact Flight Service by tuning in a local VOR, stating the VOR you are listening over, and transmitting on 122.1 MHz. Flight Service will call you back by transmitting over the VOR you stated. It is also important pilots know the local VORs along their route of flight, especially in an area of minimal coverage, for updated weather information and in the event of an emergency.

Flight Watch

Otherwise known as En Route Flight Advisory Service, Flight Watch also correlates with the local Flight Service Station, but not all Flight Service Stations are Flight Watch staffed. However, each Air Route Traffic Control Center has a correlating Flight Watch. So, whichever center's airspace you're in will be your Flight Watch. For example, in New York Center airspace, it would be 'New York Flight Watch.' Flight Watch, like in-flight, has a common frequency, 122.0 MHz. Frequency 122.0 MHz is primarily for low altitude use, due to frequency congestion, and is available for flights operating above 5,000 feet and below flight level 180, although in numerous areas, contacts are possible below 5,000 feet. High altitude Flight Watch frequencies correlate with the specific area as do Radio discrete frequencies, and are charted, shown in the inside back cover of AFD, or available on request from your Flight Watch specialist.


Hazardous In-flight Weather Advisory Service (HIWAS) is a broadcast of summarized hazardous weather advisories. It will be updated as necessary and a time will be placed on the recording. This broadcast includes radar descriptions and pilot reports. Each HIWAS covers an area within a 150 nautical mile radius of an assigned outlet. Since HIWAS updates are provided when adverse weather becomes available, there may be a crucial time delay, as adverse weather conditions are constantly changing. As with all recorded information, pay particular attention to the time of the recording and contact Flight Watch or Radio for the most current information.

A few notes about the role of Flight Service in Search and Rescue.

The purpose of filing a VFR flight plan is to have a database of correct flight information if search and rescue is needed. And, since it is an issue of search and rescue, the elements of a flight plan are very important. Of course, the N-number, type, and color of aircraft are significant for obvious reasons. However, one consistent problem remains: destination contact information. Flight Service needs a telephone number so we can contact someone immediately in case your flight plan becomes overdue. Plus, in case you fail to close your VFR flight plan, someone can call you at your destination.

Initial search and rescue procedures are started once an aircraft on a VFR or IFR activated flight plan becomes overdue, or a report is made to an air traffic facility of a missing aircraft that is not on a flight plan one hour from the actual time a reliable source reports the aircraft to be at least one hour late at the destination. Once the aircraft becomes overdue, an initial communications search is started, including a telephone call to the destination contact number you provided us when you filed your flight plan. A correct telephone number may avoid unnecessary search and rescue operations, and possible expense to aircraft owners. If an ELT signal is received, the ARTCC serves as the contact point and coordinates directly with the appropriate rescue coordination center (RCC). If not already in progress, Flight Service specialists initiate field searches, and proceed with search and rescue responsibilities.

Once a search passes the initial communications stage, one hour after the aircraft is overdue, the RCC becomes involved. Communications, air traffic, and field searches are still ongoing, but at this point, more personnel become involved'including local authorities if not already contacted to perform an after hours ramp search' which by the way, may involve removing expensive hanger locks.

Within two hours of your ETA a full and extensive search and rescue effort is underway. The search involves an area extending 50 miles on either side of the route of flight you provided us when you filed your flight plan, from the last reported position to the destination. Therefore, it is important to activate your flight plan (without that, all we have is a proposal), and make any changes in your flight plan, either prior to departure or aloft, to the local servicing Flight Service Station. All changes concerning your flight will be sent to the destination station. The information we have is the information we will use to locate your aircraft. Once safely landed, close your VFR flight plan with the destination Flight Service either on 122.2 MHz, (which is the common Flight Service frequency nationwide), or a discrete to the area frequency. If you are unable to contact Flight Service by radio, telephone it as soon as possible, or pass to air traffic to relay to Flight Service.

How to Get a Good Phone Briefing

So, how do you maximize your time on the phone with a knowledgeable weather briefer and decipher all that weather information?

Know your weather service products, ask questions, listen intently with emphasis on adverse weather and aeronautical information, and never be afraid to ask for weather and aeronautical explanations. You'll wish you had seconded guessed that weather pattern on that warm (relatively) sunny spring morning when the artic air has not completely exited the upper atmosphere, and an equally stubborn and moist southerly flow both confront to create an off-seasonal mix that can leave you questioning that 'go' decision but not before you start trying to find a safe place to land in the aftermath of unseasonable scattered thunderstorms without as much of a warning as a fair weather cloud.

Pay attention to the big atmospheric picture, but don't be too quick to ignore that early morning fog that 'has been' burning off by 8 a.m.' only to be interrupted by a stubbornly calm and yet warmer air mass, that settles the temperature/dew point spread till four in the afternoon'just days after the unending 8 a.m. trend ended.

The bottom line is that it truly is the science of weather briefing that you should seek out when making that all important preflight call. It is not just about temperature and dew point spread, or local conditions'-weather truly is the big picture and finding your picture in the essence of the briefing is a science in and of itself.

Julia Greenway is an Air Traffic Control Specialist at the Leesburg AFSS in Virginia.

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